A lot of good answers are provided above but I am going to present my(Java) viewpoint here.
Data Encapsulation simply means wrapping and controlling access of logically grouped data in a class. It is generally associated with another keyword - Data Hiding. This is achieved in Java using access modifiers.
A simple example would be defining a private variable and giving access to it using getter and setter methods or making a method private as it's only use is withing the class. There is no need for user to know about these methods and variables.
Note : It should not be misunderstood that encapsulation is all about data hiding only. When we say encapsulation, emphasis should be on grouping or packaging or bundling related data and behavior together.
Data Abstraction on the other hand is concept of generalizing so that the underneath complex logic is not exposed to the user. In Java this is achieved by using interfaces and abstract classes.
Example -
Lets say we have an interface Animal and it has a function makeSound(). There are two concrete classes Dog and Cat that implement this interface. These concrete classes have separate implementations of makeSound() function. Now lets say we have a animal(We get this from some external module). All user knows is that the object that it is receiving is some Animal and it is the users responsibility to print the animal sound. One brute force way is to check the object received to identify it's type, then typecast it to that Animal type and then call makeSound() on it. But a neater way is to abstracts thing out. Use Animal as a polymorphic reference and call makeSound() on it. At runtime depending on what the real Object type is proper function will be invoked.
More details here.
Complex logic is in the circuit board which is encapsulated in a touchpad and a nice interface(buttons) is provided to abstract it out to the user.
PS: Above links are to my personal blog.
In the definition of your Card
class, a declaration for a default construction appears:
class Card
{
// ...
Card(); // <== Declaration of default constructor!
// ...
};
But no corresponding definition is given. In fact, this function definition (from card.cpp
):
void Card() {
//nothing
}
Does not define a constructor, but rather a global function called Card
that returns void
. You probably meant to write this instead:
Card::Card() {
//nothing
}
Unless you do that, since the default constructor is declared but not defined, the linker will produce error about undefined references when a call to the default constructor is found.
The same applies to your constructor accepting two arguments. This:
void Card(Card::Rank rank, Card::Suit suit) {
cardRank = rank;
cardSuit = suit;
}
Should be rewritten into this:
Card::Card(Card::Rank rank, Card::Suit suit) {
cardRank = rank;
cardSuit = suit;
}
And the same also applies for other member functions: it seems you did not add the Card::
qualifier before the member function names in their definitions. Without it, those functions are global functions rather than definitions of member functions.
Your destructor, on the other hand, is declared but never defined. Just provide a definition for it in card.cpp
:
Card::~Card() { }
Personally I would use a classmethod whenever I needed a static method. Mainly because I get the class as an argument.
class myObj(object):
def myMethod(cls)
...
myMethod = classmethod(myMethod)
or use a decorator
class myObj(object):
@classmethod
def myMethod(cls)
For static properties.. Its time you look up some python definition.. variable can always change. There are two types of them mutable and immutable.. Also, there are class attributes and instance attributes.. Nothing really like static attributes in the sense of java & c++
Why use static method in pythonic sense, if it has no relation whatever to the class! If I were you, I'd either use classmethod or define the method independent from the class.
A simple Monads explanation with a Marvel's case study is here.
Monads are abstractions used to sequence dependent functions that are effectful. Effectful here means they return a type in form F[A] for example Option[A] where Option is F, called type constructor. Let's see this in 2 simple steps
A => C = A => B andThen B => C
However, if the function returns an effect type like Option[A] i.e. A => F[B] the composition doesn't work as to go to B we need A => B but we have A => F[B].
We need a special operator, "bind" that knows how to fuse these functions that return F[A].
A => F[C] = A => F[B] bind B => F[C]
The "bind" function is defined for the specific F.
There is also "return", of type A => F[A] for any A, defined for that specific F also. To be a Monad, F must have these two functions defined for it.
Thus we can construct an effectful function A => F[B] from any pure function A => B,
A => F[B] = A => B andThen return
but a given F can also define its own opaque "built-in" special functions of such types that a user can't define themself (in a pure language), like
When would you use private
and when would you use protected
?
Private Inheritance can be thought of Implemented in terms of relationship rather than a IS-A relationship. Simply put, the external interface of the inheriting class has no (visible) relationship to the inherited class, It uses the private
inheritance only to implement a similar functionality which the Base class provides.
Unlike, Private Inheritance, Protected inheritance is a restricted form of Inheritance,wherein the deriving class IS-A kind of the Base class and it wants to restrict the access of the derived members only to the derived class.
Why not change the constructor on Production
to let you pass in a reference at construction time:
public class Meter
{
private int _powerRating = 0;
private Production _production;
public Meter()
{
_production = new Production(this);
}
}
In the Production
constructor you can assign this to a private field or a property. Then Production
will always have access to is parent.
In Python:
self
argument.self
) or the class (cls
) argument.__init__
is a special function and without overriding __new__
it will always be given the instance of the class as its first argument.
An example using the builtin classmethod and staticmethod decorators:
import sys
class Num:
max = sys.maxint
def __init__(self,num):
self.n = num
def getn(self):
return self.n
@staticmethod
def getone():
return 1
@classmethod
def getmax(cls):
return cls.max
myObj = Num(3)
# with the appropriate decorator these should work fine
myObj.getone()
myObj.getmax()
myObj.getn()
That said, I would try to use @classmethod
/@staticmethod
sparingly. If you find yourself creating objects that consist of nothing but staticmethod
s the more pythonic thing to do would be to create a new module of related functions.
For Autodidacts:
function BaseClass(toBePrivate){
var morePrivates;
this.isNotPrivate = 'I know';
// add your stuff
}
var o = BaseClass.prototype;
// add your prototype stuff
o.stuff_is_never_private = 'whatever_except_getter_and_setter';
// MiddleClass extends BaseClass
function MiddleClass(toBePrivate){
BaseClass.call(this);
// add your stuff
var morePrivates;
this.isNotPrivate = 'I know';
}
var o = MiddleClass.prototype = Object.create(BaseClass.prototype);
MiddleClass.prototype.constructor = MiddleClass;
// add your prototype stuff
o.stuff_is_never_private = 'whatever_except_getter_and_setter';
// TopClass extends MiddleClass
function TopClass(toBePrivate){
MiddleClass.call(this);
// add your stuff
var morePrivates;
this.isNotPrivate = 'I know';
}
var o = TopClass.prototype = Object.create(MiddleClass.prototype);
TopClass.prototype.constructor = TopClass;
// add your prototype stuff
o.stuff_is_never_private = 'whatever_except_getter_and_setter';
// to be continued...
Create "instance" with getter and setter:
function doNotExtendMe(toBePrivate){
var morePrivates;
return {
// add getters, setters and any stuff you want
}
}
Just a heads up... with Python 2.7, and I believe ever since super()
was introduced in version 2.2, you can only call super()
if one of the parents inherit from a class that eventually inherits object
(new-style classes).
Personally, as for python 2.7 code, I'm going to continue using BaseClassName.__init__(self, args)
until I actually get the advantage of using super()
.
It looks much like a list of Django ORM model instances.
Why not sort them on query like this:
ut = Tag.objects.order_by('-count')
Basic thumb rule is: For "Nouns" use Abstract class and for "Verbs" use interface
E.g: car
is an abstract class and drive
, we can make it an interface.
Another option to include_once or require_once is to use class autoloading. http://php.net/manual/en/language.oop5.autoload.php
Something like this (might not work as I don't have Python around):
class IInterface:
def show(self): raise NotImplementedError
class MyClass(IInterface):
def show(self): print "Hello World!"
Compile time polymorphism(Static Binding/Early Binding): In static polymorphism, if we call a method in our code then which definition of that method is to be called actually is resolved at compile time only.
(or)
At compile time, Java knows which method to invoke by checking the method signatures. So, this is called compile-time polymorphism or static binding.
Dynamic Polymorphism(Late Binding/ Runtime Polymorphism): At run time, Java waits until runtime to determine which object is actually being pointed to by the reference. Method resolution was taken at runtime, due to that we call as run time polymorphism.
Another somewhat obscure use of __slots__
is to add attributes to an object proxy from the ProxyTypes package, formerly part of the PEAK project. Its ObjectWrapper
allows you to proxy another object, but intercept all interactions with the proxied object. It is not very commonly used (and no Python 3 support), but we have used it to implement a thread-safe blocking wrapper around an async implementation based on tornado that bounces all access to the proxied object through the ioloop, using thread-safe concurrent.Future
objects to synchronise and return results.
By default any attribute access to the proxy object will give you the result from the proxied object. If you need to add an attribute on the proxy object, __slots__
can be used.
from peak.util.proxies import ObjectWrapper
class Original(object):
def __init__(self):
self.name = 'The Original'
class ProxyOriginal(ObjectWrapper):
__slots__ = ['proxy_name']
def __init__(self, subject, proxy_name):
# proxy_info attributed added directly to the
# Original instance, not the ProxyOriginal instance
self.proxy_info = 'You are proxied by {}'.format(proxy_name)
# proxy_name added to ProxyOriginal instance, since it is
# defined in __slots__
self.proxy_name = proxy_name
super(ProxyOriginal, self).__init__(subject)
if __name__ == "__main__":
original = Original()
proxy = ProxyOriginal(original, 'Proxy Overlord')
# Both statements print "The Original"
print "original.name: ", original.name
print "proxy.name: ", proxy.name
# Both statements below print
# "You are proxied by Proxy Overlord", since the ProxyOriginal
# __init__ sets it to the original object
print "original.proxy_info: ", original.proxy_info
print "proxy.proxy_info: ", proxy.proxy_info
# prints "Proxy Overlord"
print "proxy.proxy_name: ", proxy.proxy_name
# Raises AttributeError since proxy_name is only set on
# the proxy object
print "original.proxy_name: ", proxy.proxy_name
There's no point in declaring the class as static
. Just declare its methods static
and call them from the class name as normal, like Java's Math class.
Also, even though it isn't strictly necessary to make the constructor private, it is a good idea to do so. Marking the constructor private prevents other people from creating instances of your class, then calling static methods from those instances. (These calls work exactly the same in Java, they're just misleading and hurt the readability of your code.)
From a phylosophic point of view :
An abstract class represents an "is a" relationship. Lets say I have fruits, well I would have a Fruit abstract class that shares common responsabilities and common behavior.
An interface represents a "should do" relationship. An interface, in my opinion (which is the opinion of a junior dev), should be named by an action, or something close to an action, (Sorry, can't find the word, I'm not an english native speaker) lets say IEatable. You know it can be eaten, but you don't know what you eat.
From a coding point of view :
If your objects have duplicated code, it is an indication that they have common behavior, which means you might need an abstract class to reuse the code, which you cannot do with an interface.
Another difference is that an object can implement as many interfaces as you need, but you can only have one abstract class because of the "diamond problem" (check out here to know why! http://en.wikipedia.org/wiki/Multiple_inheritance#The_diamond_problem)
I probably forget some points, but I hope it can clarify things.
PS : The "is a"/"should do" is brought by Vivek Vermani's answer, I didn't mean to steal his answer, just to reuse the terms because I liked them!
If you want a super class to call a function from a subclass, the cleanest way is to define an abstract pattern, in this manner you explicitly know the method exists somewhere and must be overridden by a subclass.
This is as an example, normally you do not call a sub method within the constructor as the sub instance is not initialized yet… (reason why you have an "undefined" in your question's example)
abstract class A {
// The abstract method the subclass will have to call
protected abstract doStuff():void;
constructor(){
alert("Super class A constructed, calling now 'doStuff'")
this.doStuff();
}
}
class B extends A{
// Define here the abstract method
protected doStuff()
{
alert("Submethod called");
}
}
var b = new B();
Test it Here
And if like @Max you really want to avoid implementing the abstract method everywhere, just get rid of it. I don't recommend this approach because you might forget you are overriding the method.
abstract class A {
constructor() {
alert("Super class A constructed, calling now 'doStuff'")
this.doStuff();
}
// The fallback method the subclass will call if not overridden
protected doStuff(): void {
alert("Default doStuff");
};
}
class B extends A {
// Override doStuff()
protected doStuff() {
alert("Submethod called");
}
}
class C extends A {
// No doStuff() overriding, fallback on A.doStuff()
}
var b = new B();
var c = new C();
Try it Here
Abstract method doesnt have an implementation.It is declared in the parent class. The child class is resposible for implementing that method.
Virtual method should have an implementation in the parent class and it facilitates the child class to make the choice whether to use that implementation of the parent class or to have a new implementation for itself for that method in child class.
One of my friends is writing a graphics app using NVIDIA CUDA. Application fits in very nicely with OOP paradigm and the problem can be decomposed into modules neatly. However, to use CUDA you need to use C, which doesn't support inheritance. Therefore, you need to be clever.
a) You devise a clever system which will emulate inheritance to a certain extent. It can be done!
i) You can use a hook system, which expects every child C of parent P to have a certain override for function F. You can make children register their overrides, which will be stored and called when required.
ii) You can use struct memory alignment feature to cast children into parents.
This can be neat but it's not easy to come up with future-proof, reliable solution. You will spend lots of time designing the system and there is no guarantee that you won't run into problems half-way through the project. Implementing multiple inheritance is even harder, if not almost impossible.
b) You can use consistent naming policy and use divide and conquer approach to create a program. It won't have any inheritance but because your functions are small, easy-to-understand and consistently formatted you don't need it. The amount of code you need to write goes up, it's very hard to stay focused and not succumb to easy solutions (hacks). However, this ninja way of coding is the C way of coding. Staying in balance between low-level freedom and writing good code. Good way to achieve this is to write prototypes using a functional language. For example, Haskell is extremely good for prototyping algorithms.
I tend towards approach b. I wrote a possible solution using approach a, and I will be honest, it felt very unnatural using that code.
There is a much easier and more compact solution for multilevel prototype lookup, but it requires Proxy
support. Usage: SUPER(<instance>).<method>(<args>)
, for example, assuming two classes A
and B extends A
with method m
: SUPER(new B).m()
.
function SUPER(instance) {
return new Proxy(instance, {
get(target, prop) {
return Object.getPrototypeOf(Object.getPrototypeOf(target))[prop].bind(target);
}
});
}
Private members (state and behavior) are inherited. They (can) affect the behavior and size of the object which is instantiated by the class. Not to mention that they are very well visible to the subclasses via all the encaptulation-breaking mechanisms that are available, or can be assumed by their implementers.
Although inheritance has a "defacto" definition, it definitely has no link to "visibility" aspects, which get assumed by the "no" answers.
So, there is no need to be diplomatic. JLS is just wrong at this point.
Any assumption that they are not "inherited" is unsafe and dangerous.
So among two defacto (partially) conflicting definitions (which I will not repeat), the only one that should be followed is the one that is safer (or safe).
There are some equivalents of constructors for when the zero values can't make sensible default values or for when some parameter is necessary for the struct initialization.
Supposing you have a struct like this :
type Thing struct {
Name string
Num int
}
then, if the zero values aren't fitting, you would typically construct an instance with a NewThing
function returning a pointer :
func NewThing(someParameter string) *Thing {
p := new(Thing)
p.Name = someParameter
p.Num = 33 // <- a very sensible default value
return p
}
When your struct is simple enough, you can use this condensed construct :
func NewThing(someParameter string) *Thing {
return &Thing{someParameter, 33}
}
If you don't want to return a pointer, then a practice is to call the function makeThing
instead of NewThing
:
func makeThing(name string) Thing {
return Thing{name, 33}
}
Reference : Allocation with new in Effective Go.
In keeping with its unbroken record of backwards-compatibility, ECMAScript 6, JavaScript still doesn't have a class
type (though not everyone understands this). It does have a class
keyword as part of its class
syntax for creating prototypes—but still no thing called class. JavaScript is not now and has never been a classical OOP language. Speaking of JS in terms of class is only either misleading or a sign of not yet grokking prototypical inheritance (just keeping it real).
That means this.constructor
is still a great way to get a reference to the constructor
function. And this.constructor.prototype
is the way to access the prototype itself. Since this isn't Java, it's not a class. It's the prototype object your instance was instantiated from. Here is an example using the ES6 syntactic sugar for creating a prototype chain:
class Foo {
get foo () {
console.info(this.constructor, this.constructor.name)
return 'foo'
}
}
class Bar extends Foo {
get foo () {
console.info('[THIS]', this.constructor, this.constructor.name, Object.getOwnPropertyNames(this.constructor.prototype))
console.info('[SUPER]', super.constructor, super.constructor.name, Object.getOwnPropertyNames(super.constructor.prototype))
return `${super.foo} + bar`
}
}
const bar = new Bar()
console.dir(bar.foo)
This is what that outputs using babel-node
:
> $ babel-node ./foo.js ? 6.2.0 [±master ?]
[THIS] [Function: Bar] 'Bar' [ 'constructor', 'foo' ]
[SUPER] [Function: Foo] 'Foo' [ 'constructor', 'foo' ]
[Function: Bar] 'Bar'
'foo + bar'
There you have it! In 2016, there's a class
keyword in JavaScript, but still no class type. this.constructor
is the best way to get the constructor function, this.constructor.prototype
the best way to get access to the prototype itself.
A sub class is a small file of a program that extends from some other class. For example you make a class about cars in general and have basic information that holds true for all cars with your constructors and stuff then you have a class that extends from that on a more specific car or line of cars that would have new variables/methods. I see you already have plenty of examples of code from above by the time I get to post this but I hope this description helps.
You could define a clone function.
I use this one :
function goclone(source) {
if (Object.prototype.toString.call(source) === '[object Array]') {
var clone = [];
for (var i=0; i<source.length; i++) {
clone[i] = goclone(source[i]);
}
return clone;
} else if (typeof(source)=="object") {
var clone = {};
for (var prop in source) {
if (source.hasOwnProperty(prop)) {
clone[prop] = goclone(source[prop]);
}
}
return clone;
} else {
return source;
}
}
var B = goclone(A);
It doesn't copy the prototype, functions, and so on. But you should adapt it (and maybe simplify it) for you own need.
const int WIDTH = 1024;
const int HEIGHT = 800;
for example we have a
class Employee
{
int getsalary()
{return 0;}
String getDesignation()
{
return “default”;
}
}
class Manager extends Employee
{
int getsalary()
{
return 20000;
}
String getDesignation()
{
return “Manager”
}
}
class SoftwareEngineer extends Employee
{
int getsalary()
{
return 20000;
}
String getDesignation()
{
return “Manager”
}
}
now if you want to set or get salary and designation of all employee (i.e software enginerr,manager etc )
we will take an array of Employee and call both method getsalary(),getDesignation
Employee arr[]=new Employee[10];
arr[1]=new SoftwareEngieneer();
arr[2]=new Manager();
arr[n]=…….
for(int i;i>arr.length;i++)
{
System.out.println(arr[i].getDesignation+””+arr[i].getSalary())
}
now its an kind of loose coupling because you can have different types of employees ex:softeware engineer,manager,hr,pantryEmployee etc
so you can give object to the parent reference irrespective of different employee object
Properties have the primary advantage of allowing you to change the way data on an object is accessed without breaking it's public interface. For example, if you need to add extra validation, or to change a stored field into a calculated you can do so easily if you initially exposed the field as a property. If you just exposed a field directly, then you would have to change the public interface of your class to add the new functionality. That change would break existing clients, requiring them to be recompiled before they could use the new version of your code.
If you write a class library designed for wide consumption (like the .NET Framework, which is used by millions of people), that can be a problem. However, if you are writing a class used internally inside a small code base (say <= 50 K lines), it's really not a big deal, because no one would be adversely affected by your changes. In that case it really just comes down to personal preference.
Encapsulation
Encapsulation from what you have learnt googling around, is a concept of combining the related data and operations in a single capsule or what we could say a class in OOP, such that no other program can modify the data it holds or method implementation it has, at a particular instance of time. Only the getter and setter methods can provide access to the instance variables.
Our code might be used by others and future up-gradations or bug fixes are liable. Encapsulation is something that makes sure that whatever code changes we do in our code doesn't break the code of others who are using it.
Encapsulation adds up to the maintainability, flexibility and extensibility of the code.
Encapsulation helps hide the implementation behind an interface.
Abstraction
Abstraction is the process of actually hiding the implementation behind an interface. So we are just aware of the actual behavior but not how exactly the think works out internally. The most common example could the scenario where put a key inside the lock and easily unlock it. So the interface here is the keyhole, while we are not aware of how the levers inside the lock co-ordinate among themselves to get the lock unlocked.
To be more clear, abstraction can be explained as the capability to use the same interface for different objects. Different implementations of the same interface can exist, while the details of every implementation are hidden by encapsulation.
Finally, the statement to answer all the confusions until now - The part that is hidden relates to encapsulation while the part that is exposed relates to abstraction.
For example two class A,B having same method m1(). And class C extends both A, B.
class C extends A, B // for explaining purpose.
Now, class C will search the definition of m1. First, it will search in class if it didn't find then it will check to parents class. Both A, B having the definition So here ambiguity occur which definition should choose. So JAVA DOESN'T SUPPORT MULTIPLE INHERITANCE.
Use
$this
to refer to the current object. Useself
to refer to the current class. In other words, use$this->member
for non-static members, useself::$member
for static members.
Here is an example of correct usage of $this
and self
for non-static and static member variables:
<?php
class X {
private $non_static_member = 1;
private static $static_member = 2;
function __construct() {
echo $this->non_static_member . ' '
. self::$static_member;
}
}
new X();
?>
Here is an example of incorrect usage of $this
and self
for non-static and static member variables:
<?php
class X {
private $non_static_member = 1;
private static $static_member = 2;
function __construct() {
echo self::$non_static_member . ' '
. $this->static_member;
}
}
new X();
?>
Here is an example of polymorphism with $this
for member functions:
<?php
class X {
function foo() {
echo 'X::foo()';
}
function bar() {
$this->foo();
}
}
class Y extends X {
function foo() {
echo 'Y::foo()';
}
}
$x = new Y();
$x->bar();
?>
Here is an example of suppressing polymorphic behaviour by using self
for member functions:
<?php
class X {
function foo() {
echo 'X::foo()';
}
function bar() {
self::foo();
}
}
class Y extends X {
function foo() {
echo 'Y::foo()';
}
}
$x = new Y();
$x->bar();
?>
The idea is that
$this->foo()
calls thefoo()
member function of whatever is the exact type of the current object. If the object is oftype X
, it thus callsX::foo()
. If the object is oftype Y
, it callsY::foo()
. But with self::foo(),X::foo()
is always called.
From http://www.phpbuilder.com/board/showthread.php?t=10354489:
I think the question is getting at the fact that C# needs another keyword, for precisely this sort of situation. You want a method whose return value depends only on the type on which it is called. You can't call it "static" if said type is unknown. But once the type becomes known, it will become static. "Unresolved static" is the idea -- it's not static yet, but once we know the receiving type, it will be. This is a perfectly good concept, which is why programmers keep asking for it. But it didn't quite fit into the way the designers thought about the language.
Since it's not available, I have taken to using non-static methods in the way shown below. Not exactly ideal, but I can't see any approach that makes more sense, at least not for me.
public interface IZeroWrapper<TNumber> {
TNumber Zero {get;}
}
public class DoubleWrapper: IZeroWrapper<double> {
public double Zero { get { return 0; } }
}
Polymorphism relates to the ability of a language to have different object treated uniformly by using a single interfaces; as such it is related to overriding, so the interface (or the base class) is polymorphic, the implementor is the object which overrides (two faces of the same medal)
anyway, the difference between the two terms is better explained using other languages, such as c++: a polymorphic object in c++ behaves as the java counterpart if the base function is virtual, but if the method is not virtual the code jump is resolved statically, and the true type not checked at runtime so, polymorphism include the ability for an object to behave differently depending on the interface used to access it; let me make an example in pseudocode:
class animal {
public void makeRumor(){
print("thump");
}
}
class dog extends animal {
public void makeRumor(){
print("woff");
}
}
animal a = new dog();
dog b = new dog();
a.makeRumor() -> prints thump
b.makeRumor() -> prints woff
(supposing that makeRumor is NOT virtual)
java doesn't truly offer this level of polymorphism (called also object slicing).
animal a = new dog(); dog b = new dog();
a.makeRumor() -> prints thump
b.makeRumor() -> prints woff
on both case it will only print woff.. since a and b is refering to class dog
Polymorphism is the ability to treat a class of object as if it is the parent class.
For instance, suppose there is a class called Animal, and a class called Dog that inherits from Animal. Polymorphism is the ability to treat any Dog object as an Animal object like so:
Dog* dog = new Dog;
Animal* animal = dog;
You can't achieve multiple inheritance with abstract class, that is why Sun Microsystems provide interfaces.
You cannot extend two classes but you can implement multiple interfaces.
Variable set outside __init__
belong to the class. They're shared by all instances.
Variables created inside __init__
(and all other method functions) and prefaced with self.
belong to the object instance.
In this simple case you can use vars()
:
an = Animal()
attrs = vars(an)
# {'kids': 0, 'name': 'Dog', 'color': 'Spotted', 'age': 10, 'legs': 2, 'smell': 'Alot'}
# now dump this in some way or another
print(', '.join("%s: %s" % item for item in attrs.items()))
If you want to store Python objects on the disk you should look at shelve — Python object persistence.
Actually, I believe you want to use the __getattr__
special method instead.
Quote from the Python docs:
__getattr__( self, name)
Called when an attribute lookup has not found the attribute in the usual places (i.e. it is not an instance attribute nor is it found in the class tree for self). name is the attribute name. This method should return the (computed) attribute value or raise an AttributeError exception.
Note that if the attribute is found through the normal mechanism,__getattr__()
is not called. (This is an intentional asymmetry between__getattr__()
and__setattr__()
.) This is done both for efficiency reasons and because otherwise__setattr__()
would have no way to access other attributes of the instance. Note that at least for instance variables, you can fake total control by not inserting any values in the instance attribute dictionary (but instead inserting them in another object). See the__getattribute__()
method below for a way to actually get total control in new-style classes.
Note: for this to work, the instance should not have a test
attribute, so the line self.test=20
should be removed.
It does, in that a high-level functional PL (like OCaml, with classes, modules, etc.) certainly supersedes OOP imperative languages in type versatility and power of expression. The abstractions do not leak, you can express most of your ideas directly in the program. Therefore, yes, it does replace design patterns, most of which are ridiculously simplistic compared to functional patterns anyhow.
To sum it up,in object oriented programming, everything is modeled into classes and objects. Classes contain properties and methods. Public, private and protected keywords are used to specify access to these members(properties and methods) of a class from other classes or other .dlls or even other applications.
The Abstract Factory pattern is used in various places.
E.g., DatagramSocketImplFactory
, PreferencesFactory
. There are many more---search the Javadoc for interfaces which have the word "Factory" in their name.
Also there are quite a few instances of the Factory pattern, too.
Properties have values only in objects, not classes.
If you need to store something for all objects of a class, you have to use a global variable. You can hide it by declaring it static
in the implementation file.
You may also consider using specific relations between your objects: you attribute a role of master to a specific object of your class and link others objects to this master. The master will hold the dictionary as a simple property. I think of a tree like the one used for the view hierarchy in Cocoa applications.
Another option is to create an object of a dedicated class that is composed of both your 'class' dictionary and a set of all the objects related to this dictionary. This is something like NSAutoreleasePool
in Cocoa.
In addition to the already selected answer (and the various informative posts here), I would highly recommend grabbing a copy of Head First Design Patterns. It is a very easy read and will answer your question directly, explain why it is important, and show you many programming patterns you can use to make use of that principle (and others).
It is simple, $obj->{$obj->Name} the curly brackets will wrap the property much like a variable variable.
This was a top search. But did not resolve my question, which was using $this. In the case of my circumstance using the curly bracket also helped...
example with Code Igniter get instance
in an sourced library class called something with a parent class instance
$this->someClass='something';
$this->someID=34;
the library class needing to source from another class also with the parents instance
echo $this->CI->{$this->someClass}->{$this->someID};
I generally prefer to write regular non static classes and use a factory class to instantiate single ( sudo static ) instances of the object.
This way constructor and destructor work as per normal, and I can create additional non static instances if I wish ( for example a second DB connection )
I use this all the time and is especially useful for creating custom DB store session handlers, as when the page terminates the destructor will push the session to the database.
Another advantage is you can ignore the order you call things as everything will be setup on demand.
class Factory {
static function &getDB ($construct_params = null)
{
static $instance;
if( ! is_object($instance) )
{
include_once("clsDB.php");
$instance = new clsDB($construct_params); // constructor will be called
}
return $instance;
}
}
The DB class...
class clsDB {
$regular_public_variables = "whatever";
function __construct($construct_params) {...}
function __destruct() {...}
function getvar() { return $this->regular_public_variables; }
}
Anywhere you want to use it just call...
$static_instance = &Factory::getDB($somekickoff);
Then just treat all methods as non static ( because they are )
echo $static_instance->getvar();
An interface is one of the more overloaded and confusing terms in development.
It is actually a concept of abstraction and encapsulation. For a given "box", it declares the "inputs" and "outputs" of that box. In the world of software, that usually means the operations that can be invoked on the box (along with arguments) and in some cases the return types of these operations.
What it does not do is define what the semantics of these operations are, although it is commonplace (and very good practice) to document them in proximity to the declaration (e.g., via comments), or to pick good naming conventions. Nevertheless, there are no guarantees that these intentions would be followed.
Here is an analogy: Take a look at your television when it is off. Its interface are the buttons it has, the various plugs, and the screen. Its semantics and behavior are that it takes inputs (e.g., cable programming) and has outputs (display on the screen, sound, etc.). However, when you look at a TV that is not plugged in, you are projecting your expected semantics into an interface. For all you know, the TV could just explode when you plug it in. However, based on its "interface" you can assume that it won't make any coffee since it doesn't have a water intake.
In object oriented programming, an interface generally defines the set of methods (or messages) that an instance of a class that has that interface could respond to.
What adds to the confusion is that in some languages, like Java, there is an actual interface with its language specific semantics. In Java, for example, it is a set of method declarations, with no implementation, but an interface also corresponds to a type and obeys various typing rules.
In other languages, like C++, you do not have interfaces. A class itself defines methods, but you could think of the interface of the class as the declarations of the non-private methods. Because of how C++ compiles, you get header files where you could have the "interface" of the class without actual implementation. You could also mimic Java interfaces with abstract classes with pure virtual functions, etc.
An interface is most certainly not a blueprint for a class. A blueprint, by one definition is a "detailed plan of action". An interface promises nothing about an action! The source of the confusion is that in most languages, if you have an interface type that defines a set of methods, the class that implements it "repeats" the same methods (but provides definition), so the interface looks like a skeleton or an outline of the class.
I have done something like this and it works like a charm.
Simple.
P.S. There is more the the object but I just posted the relevant part.
var exScript = (function (undefined) {
function exScript() {
this.logInfo = [];
var that = this;
this.logInfo.push = function(e) {
that.logInfo[that.logInfo.length] = e;
console.log(e);
};
}
})();
The wording of your question is odd - Abstraction vs Encapsulation? It should be - someone explain abstraction and encapsulation...
Abstraction is understanding the essence of the thing.
A real world example is abstract art. The artists of this style try to capture/paint the essence of the thing that still allows it to be the thing. This brown smear of 4 lines captures the essence of what a bull is.
Encapsulation is black boxing.
A cell phone is a great example. I have no idea how the cell phone connects to a satellite, tower, or another phone. I have no idea how the damn thing understands my key presses or how it takes and sends pictures to an email address or another phone number. I have no idea about the intricate details of most of how a modern smart phone works. But, I can use it! The phones have standard interfaces (yes - both literal and software design) that allows someone who understand the basics of one to use almost all of them.
How are the two related?
Both abstraction and encapsulation are underlying foundations of object oriented thought and design. So, in our cell phone example. The notion of a smart phone is an abstraction, within which certain features and services are encapsulated. The iPhone and Galaxy are further abstractions of the higher level abstraction. Your physical iPhone or Galaxy are concrete examples of multiple layers of abstractions which contain encapsulated features and services.
The correct answer to this is that you shouldn't. If you want this type of thing either just use a dict, or you'll need to explicitly add attributes to some container. You can automate that by learning about decorators.
In particular, by the way, method1 in your example is just as good of an attribute.
Using the trick
Attribute VB_PredeclaredId = True
I found another more compact way:
Option Explicit
Option Base 0
Option Compare Binary
Private v_cBox As ComboBox
'
' Class creaor
Public Function New_(ByRef cBox As ComboBox) As ComboBoxExt_c
If Me Is ComboBoxExt_c Then
Set New_ = New ComboBoxExt_c
Call New_.New_(cBox)
Else
Set v_cBox = cBox
End If
End Function
As you can see the New_ constructor is called to both create and set the private members of the class (like init) only problem is, if called on the non-static instance it will re-initialize the private member. but that can be avoided by setting a flag.
If it can be of any help, I recently released a Python library named Gorilla to make the process of monkey patching more convenient.
Using a function needle()
to patch a module named guineapig
goes as follows:
import gorilla
import guineapig
@gorilla.patch(guineapig)
def needle():
print("awesome")
But it also takes care of more interesting use cases as shown in the FAQ from the documentation.
The code is available on GitHub.
Javascript is not an object oriented language as typically considered, mainly due to lack of true inheritance, DUCK typing allows for a semi-true form of inheritance/polymorphism along with the Object.prototype allowing for complex function sharing. At its heart however the lack of inheritance leads to a weak polymorphism to take place since the DUCK typing will insist some object with the same attribute names are an instance of an Object which they were not intended to be used as. Thus adding attributes to random object transforms their type's base in a manner of speaking.
You might implement your class model by composition, having the book object have a map of chapter objects contained within it (map chapter number to chapter object). Your search function could be given a list of books into which to search by asking each book to search its chapters. The book object would then iterate over each chapter, invoking the chapter.search() function to look for the desired key and return some kind of index into the chapter. The book's search() would then return some data type which could combine a reference to the book and some way to reference the data that it found for the search. The reference to the book could be used to get the name of the book object that is associated with the collection of chapter search hits.
One use for metaclasses is adding new properties and methods to an instance automatically.
For example, if you look at Django models, their definition looks a bit confusing. It looks as if you are only defining class properties:
class Person(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
However, at runtime the Person objects are filled with all sorts of useful methods. See the source for some amazing metaclassery.
If you only want one class, use an array of struct
s as the "objects" data and pass pointers to them to the "member" functions. You can use typedef struct _whatever Whatever
before declaring struct _whatever
to hide the implementation from client code. There's no difference between such an "object" and the C standard library FILE
object.
If you want more than one class with inheritance and virtual functions, then it's common to have pointers to the functions as members of the struct, or a shared pointer to a table of virtual functions. The GObject library uses both this and the typedef trick, and is widely used.
There's also a book on techniques for this available online - Object Oriented Programming with ANSI C.
One Short Answere is:
Just call the "type" built in using three parameters, like this:
ClassName = type("ClassName", (Base1, Base2,...), classdictionary)
update as stated in the comment bellow this is not the answer to this question at all. I will keep it undeleted, since there are hints some people get here trying to dynamically create classes - which is what the line above does.
To create an object of a class one has a reference too, as put in the accepted answer, one just have to call the class:
instance = ClassObject()
The mechanism for instantiation is thus:
Python does not use the new
keyword some languages use - instead it's data model explains the mechanism used to create an instantance of a class when it is called with the same syntax as any other callable:
Its class' __call__
method is invoked (in the case of a class, its class is the "metaclass" - which is usually the built-in type
). The normal behavior of this call is to invoke the (pseudo) static __new__
method on the class being instantiated, followed by its __init__
. The __new__
method is responsible for allocating memory and such, and normally is done by the __new__
of object
which is the class hierarchy root.
So calling ClassObject()
invokes ClassObject.__class__.call()
(which normally will be type.__call__
) this __call__
method will receive ClassObject itself as the first parameter - a Pure Python implementation would be like this: (the cPython version is of course, done in C, and with lots of extra code for cornercases and optimizations)
class type:
...
def __call__(cls, *args, **kw):
constructor = getattr(cls, "__new__")
instance = constructor(cls) if constructor is object.__new__ else constructor(cls, *args, **kw)
instance.__init__(cls, *args, **kw)
return instance
(I don't recall seeing on the docs the exact justification (or mechanism) for suppressing extra parameters to the root __new__
and passing it to other classes - but it is what happen "in real life" - if object.__new__
is called with any extra parameters it raises a type error - however, any custom implementation of a __new__
will get the extra parameters normally)
I'm surprised AutoMapper hasn't come up as an answer.
As is clear from all the previous answers, you cannot do the typecast. However, using AutoMapper, in a few lines of code you can have a new SkyfilterClient
instantiated based on an existing NetworkClient
.
In essence, you would put the following where you are currently doing your typecasting:
using AutoMapper;
...
// somewhere, your network client was declared
var existingNetworkClient = new NetworkClient();
...
// now we want to type-cast, but we can't, so we instantiate using AutoMapper
AutoMapper.Mapper.CreateMap<NetworkClient, SkyfilterClient>();
var skyfilterObject = AutoMapper.Mapper.Map<SkyfilterClient>(existingNetworkClient);
Here's a full-blown example:
public class Vehicle
{
public int NumWheels { get; set; }
public bool HasMotor { get; set; }
}
public class Car: Vehicle
{
public string Color { get; set; }
public string SteeringColumnStyle { get; set; }
}
public class CarMaker
{
// I am given vehicles that I want to turn into cars...
public List<Car> Convert(List<Vehicle> vehicles)
{
var cars = new List<Car>();
AutoMapper.Mapper.CreateMap<Vehicle, Car>(); // Declare that we want some automagic to happen
foreach (var vehicle in vehicles)
{
var car = AutoMapper.Mapper.Map<Car>(vehicle);
// At this point, the car-specific properties (Color and SteeringColumnStyle) are null, because there are no properties in the Vehicle object to map from.
// However, car's NumWheels and HasMotor properties which exist due to inheritance, are populated by AutoMapper.
cars.Add(car);
}
return cars;
}
}
Another Python BST with sort key (defaulting to value)
LEFT = 0
RIGHT = 1
VALUE = 2
SORT_KEY = -1
class BinarySearchTree(object):
def __init__(self, sort_key=None):
self._root = []
self._sort_key = sort_key
self._len = 0
def insert(self, val):
if self._sort_key is None:
sort_key = val // if no sort key, sort key is value
else:
sort_key = self._sort_key(val)
node = self._root
while node:
if sort_key < node[_SORT_KEY]:
node = node[LEFT]
else:
node = node[RIGHT]
if sort_key is val:
node[:] = [[], [], val]
else:
node[:] = [[], [], val, sort_key]
self._len += 1
def minimum(self):
return self._extreme_node(LEFT)[VALUE]
def maximum(self):
return self._extreme_node(RIGHT)[VALUE]
def find(self, sort_key):
return self._find(sort_key)[VALUE]
def _extreme_node(self, side):
if not self._root:
raise IndexError('Empty')
node = self._root
while node[side]:
node = node[side]
return node
def _find(self, sort_key):
node = self._root
while node:
node_key = node[SORT_KEY]
if sort_key < node_key:
node = node[LEFT]
elif sort_key > node_key:
node = node[RIGHT]
else:
return node
raise KeyError("%r not found" % sort_key)
I wrote up the answer for another question, though this is a more accurate question for it.
How do constructors and destructors work?
Here is a slightly opinionated answer.
Don't use __del__
. This is not C++ or a language built for destructors. The __del__
method really should be gone in Python 3.x, though I'm sure someone will find a use case that makes sense. If you need to use __del__
, be aware of the basic limitations per http://docs.python.org/reference/datamodel.html:
__del__
is called when the garbage collector happens to be collecting the objects, not when you lose the last reference to an object and not when you execute del object
.__del__
is responsible for calling any __del__
in a superclass, though it is not clear if this is in method resolution order (MRO) or just calling each superclass.__del__
means that the garbage collector gives up on detecting and cleaning any cyclic links, such as losing the last reference to a linked list. You can get a list of the objects ignored from gc.garbage. You can sometimes use weak references to avoid the cycle altogether. This gets debated now and then: see http://mail.python.org/pipermail/python-ideas/2009-October/006194.html.__del__
function can cheat, saving a reference to an object, and stopping the garbage collection.__del__
are ignored.__del__
complements __new__
far more than __init__
. This gets confusing. See http://www.algorithm.co.il/blogs/programming/python-gotchas-1-del-is-not-the-opposite-of-init/ for an explanation and gotchas.__del__
is not a "well-loved" child in Python. You will notice that sys.exit() documentation does not specify if garbage is collected before exiting, and there are lots of odd issues. Calling the __del__
on globals causes odd ordering issues, e.g., http://bugs.python.org/issue5099. Should __del__
called even if the __init__
fails? See http://mail.python.org/pipermail/python-dev/2000-March/thread.html#2423 for a long thread.But, on the other hand:
__del__
means you do not forget to call a close statement. See http://eli.thegreenplace.net/2009/06/12/safely-using-destructors-in-python/ for a pro __del__
viewpoint. This is usually about freeing ctypes or some other special resource.And my pesonal reason for not liking the __del__
function.
__del__
it devolves into thirty messages of confusion.So, find a reason not to use __del__
.
Abstraction is like using a computer.
You have absolutely no idea what's going on with it beyond what you see with the GUI (graphical user interface) and external hardware (e.g. screen). All those pretty colors and such. You're only presented the details relevant to you as a generic consumer.
Encapsulation is the actual act of hiding the irrelevant details.
You use your computer, but you don't see what its CPU (central processing unit) looks like (unless you try to break into it). It's hidden (or encapsulated) behind all that chrome and plastic.
In the context of OOP (object-oriented programming) languages, you usually have this kind of setup:
CLASS {
METHOD {
*the actual code*
}
}
An example of "encapsulation" would be having a METHOD that the regular user can't see (private). "Abstraction" is the regular user using the METHOD that they can (public) in order to use the private one.
Here's the way to do it without using any external libraries:
// Define a class like this
function Person(name, gender){
// Add object properties like this
this.name = name;
this.gender = gender;
}
// Add methods like this. All Person objects will be able to invoke this
Person.prototype.speak = function(){
alert("Howdy, my name is" + this.name);
};
// Instantiate new objects with 'new'
var person = new Person("Bob", "M");
// Invoke methods like this
person.speak(); // alerts "Howdy, my name is Bob"
Now the real answer is a whole lot more complex than that. For instance, there is no such thing as classes in JavaScript. JavaScript uses a prototype
-based inheritance scheme.
In addition, there are numerous popular JavaScript libraries that have their own style of approximating class-like functionality in JavaScript. You'll want to check out at least Prototype and jQuery.
Deciding which of these is the "best" is a great way to start a holy war on Stack Overflow. If you're embarking on a larger JavaScript-heavy project, it's definitely worth learning a popular library and doing it their way. I'm a Prototype guy, but Stack Overflow seems to lean towards jQuery.
As far as there being only "one way to do it", without any dependencies on external libraries, the way I wrote is pretty much it.
The Basics:
String
is an immutable class, it can't be changed.
StringBuilder
is a mutable class that can be appended to, characters replaced or removed and ultimately converted to a String
StringBuffer
is the original synchronized version of StringBuilder
You should prefer StringBuilder
in all cases where you have only a single thread accessing your object.
The Details:
Also note that StringBuilder/Buffers
aren't magic, they just use an Array as a backing object and that Array has to be re-allocated when ever it gets full. Be sure and create your StringBuilder/Buffer
objects large enough originally where they don't have to be constantly re-sized every time .append()
gets called.
The re-sizing can get very degenerate. It basically re-sizes the backing Array to 2 times its current size every time it needs to be expanded. This can result in large amounts of RAM getting allocated and not used when StringBuilder/Buffer
classes start to grow large.
In Java String x = "A" + "B";
uses a StringBuilder
behind the scenes. So for simple cases there is no benefit of declaring your own. But if you are building String
objects that are large, say less than 4k, then declaring StringBuilder sb = StringBuilder(4096);
is much more efficient than concatenation or using the default constructor which is only 16 characters. If your String
is going to be less than 10k then initialize it with the constructor to 10k to be safe. But if it is initialize to 10k then you write 1 character more than 10k, it will get re-allocated and copied to a 20k array. So initializing high is better than to low.
In the auto re-size case, at the 17th character the backing Array gets re-allocated and copied to 32 characters, at the 33th character this happens again and you get to re-allocated and copy the Array into 64 characters. You can see how this degenerates to lots of re-allocations and copies which is what you really are trying to avoid using StringBuilder/Buffer
in the first place.
This is from the JDK 6 Source code for AbstractStringBuilder
void expandCapacity(int minimumCapacity) {
int newCapacity = (value.length + 1) * 2;
if (newCapacity < 0) {
newCapacity = Integer.MAX_VALUE;
} else if (minimumCapacity > newCapacity) {
newCapacity = minimumCapacity;
}
value = Arrays.copyOf(value, newCapacity);
}
A best practice is to initialize the StringBuilder/Buffer
a little bit larger than you think you are going to need if you don't know right off hand how big the String
will be but you can guess. One allocation of slightly more memory than you need is going to be better than lots of re-allocations and copies.
Also beware of initializing a StringBuilder/Buffer
with a String
as that will only allocated the size of the String + 16 characters, which in most cases will just start the degenerate re-allocation and copy cycle that you are trying to avoid. The following is straight from the Java 6 source code.
public StringBuilder(String str) {
super(str.length() + 16);
append(str);
}
If you by chance do end up with an instance of StringBuilder/Buffer
that you didn't create and can't control the constructor that is called, there is a way to avoid the degenerate re-allocate and copy behavior. Call .ensureCapacity()
with the size you want to ensure your resulting String
will fit into.
The Alternatives:
Just as a note, if you are doing really heavy String
building and manipulation, there is a much more performance oriented alternative called Ropes.
Another alternative, is to create a StringList
implemenation by sub-classing ArrayList<String>
, and adding counters to track the number of characters on every .append()
and other mutation operations of the list, then override .toString()
to create a StringBuilder
of the exact size you need and loop through the list and build the output, you can even make that StringBuilder
an instance variable and 'cache' the results of .toString()
and only have to re-generate it when something changes.
Also don't forget about String.format()
when building fixed formatted output, which can be optimized by the compiler as they make it better.
When would you choose to use struct and when to use class in C++?
I use struct
when I define functors
and POD
. Otherwise I use class
.
// '()' is public by default!
struct mycompare : public std::binary_function<int, int, bool>
{
bool operator()(int first, int second)
{ return first < second; }
};
class mycompare : public std::binary_function<int, int, bool>
{
public:
bool operator()(int first, int second)
{ return first < second; }
};
First, as for your Athlete class, you can remove your Getter and Setter
methods since you have declared your instance variables with an access modifier of public
. You can access the variables via <ClassName>.<variableName>
.
However, if you really want to use that Getter and Setter
, change the public
modifier to private
instead.
Second, for the constructor, you're trying to do a simple technique called shadowing
. Shadowing
is when you have a method having a parameter with the same name as the declared variable. This is an example of shadowing
:
----------Shadowing sample----------
You have the following class:
public String name;
public Person(String name){
this.name = name; // This is Shadowing
}
In your main method for example, you instantiate the Person
class as follow:
Person person = new Person("theolc");
Variable name
will be equal to "theolc"
.
----------End of shadowing----------
Let's go back to your question, if you just want to print the first element with your current code, you may remove the Getter and Setter
. Remove your parameters on your constructor
.
public class Athlete {
public String[] name = {"Art", "Dan", "Jen"};
public String[] country = {"Canada", "Germany", "USA"};
public Athlete() {
}
In your main method, you could do this.
public static void main(String[] args) {
Athlete art = new Athlete();
System.out.println(art.name[0]);
System.out.println(art.country[0]);
}
}
It bugged me too to find a solution to mimic interfaces with the lower impacts possible.
One solution could be to make a tool :
/**
@parameter {Array|object} required : method name list or members types by their name
@constructor
*/
let Interface=function(required){
this.obj=0;
if(required instanceof Array){
this.obj={};
required.forEach(r=>this.obj[r]='function');
}else if(typeof(required)==='object'){
this.obj=required;
}else {
throw('Interface invalid parameter required = '+required);
}
};
/** check constructor instance
@parameter {object} scope : instance to check.
@parameter {boolean} [strict] : if true -> throw an error if errors ar found.
@constructor
*/
Interface.prototype.check=function(scope,strict){
let err=[],type,res={};
for(let k in this.obj){
type=typeof(scope[k]);
if(type!==this.obj[k]){
err.push({
key:k,
type:this.obj[k],
inputType:type,
msg:type==='undefined'?'missing element':'bad element type "'+type+'"'
});
}
}
res.success=!err.length;
if(err.length){
res.msg='Class bad structure :';
res.errors=err;
if(strict){
let stk = new Error().stack.split('\n');
stk.shift();
throw(['',res.msg,
res.errors.map(e=>'- {'+e.type+'} '+e.key+' : '+e.msg).join('\n'),
'','at :\n\t'+stk.join('\n\t')
].join('\n'));
}
}
return res;
};
Exemple of use :
// create interface tool
let dataInterface=new Interface(['toData','fromData']);
// abstract constructor
let AbstractData=function(){
dataInterface.check(this,1);// check extended element
};
// extended constructor
let DataXY=function(){
AbstractData.apply(this,[]);
this.xy=[0,0];
};
DataXY.prototype.toData=function(){
return [this.xy[0],this.xy[1]];
};
// should throw an error because 'fromData' is missing
let dx=new DataXY();
With classes
class AbstractData{
constructor(){
dataInterface.check(this,1);
}
}
class DataXY extends AbstractData{
constructor(){
super();
this.xy=[0,0];
}
toData(){
return [this.xy[0],this.xy[1]];
}
}
It's still a bit performance consumming and require dependancy to the Interface class, but can be of use for debug or open api.
Maybe an example from ruby can help:
You can include the mixin Comparable
and define one function "<=>(other)"
, the mixin provides all those functions:
<(other)
>(other)
==(other)
<=(other)
>=(other)
between?(other)
It does this by invoking <=>(other)
and giving back the right result.
"instance <=> other"
returns 0 if both objects are equal, less than 0 if instance
is bigger than other
and more than 0 if other
is bigger.
This rule is a complete nonsense. Why?
The reason is that in every case it is possible to tell whether to use composition or inheritance. This is determined by the answer to a question: "IS something A something else" or "HAS something A something else".
You cannot "prefer" to make something to be something else or to have something else. Strict logical rules apply.
Also there are no "contrived examples" because in every situation an answer to this question can be given.
If you cannot answer this question there is something else wrong. This includes overlapping responsibilities of classess which are usually the result of wrong use of interfaces, less often by rewriting same code in different classess.
To avoid this situations I also recommend to use good names for classes , that fully resemble their responsibilities.
A great example of how interfaces are used is in the Collections framework. If you write a function that takes a List
, then it doesn't matter if the user passes in a Vector
or an ArrayList
or a HashList
or whatever. And you can pass that List
to any function requiring a Collection
or Iterable
interface too.
This makes functions like Collections.sort(List list)
possible, regardless of how the List
is implemented.
Though both Inheritance and Composition provides code reusablility, main difference between Composition and Inheritance in Java is that Composition allows reuse of code without extending it but for Inheritance you must extend the class for any reuse of code or functionality. Another difference which comes from this fact is that by using Composition you can reuse code for even final class which is not extensible but Inheritance cannot reuse code in such cases. Also by using Composition you can reuse code from many classes as they are declared as just a member variable, but with Inheritance you can reuse code form just one class because in Java you can only extend one class, because multiple Inheritance is not supported in Java. You can do this in C++ though because there one class can extend more than one class. BTW, You should always prefer Composition over Inheritance in Java, its not just me but even Joshua Bloch has suggested in his book
Encapsulation is a strategy used as part of abstraction. Encapsulation refers to the state of objects - objects encapsulate their state and hide it from the outside; outside users of the class interact with it through its methods, but cannot access the classes state directly. So the class abstracts away the implementation details related to its state.
Abstraction is a more generic term, it can also be achieved by (amongst others) subclassing. For example, the interface List
in the standard library is an abstraction for a sequence of items, indexed by their position, concrete examples of a List
are an ArrayList
or a LinkedList
. Code that interacts with a List
abstracts over the detail of which kind of a list it is using.
Abstraction is often not possible without hiding underlying state by encapsulation - if a class exposes its internal state, it can't change its inner workings, and thus cannot be abstracted.
Technically speaking, you can only extend one class at a time and implement multiple interfaces, but when laying hands on software engineering, I would rather suggest a problem specific solution not generally answerable. By the way, it is good OO practice, not to extend concrete classes/only extend abstract classes to prevent unwanted inheritance behavior - there is no such thing as an "animal" and no use of an animal object but only concrete animals.
Source: http://jasonroell.com/2014/12/09/interfaces-vs-abstract-classes-what-should-you-use/
C# is a wonderful language that has matured and evolved over the last 14 years. This is great for us developers because a mature language provides us with a plethora of language features that are at our disposal.
However, with much power becomes much responsibility. Some of these features can be misused, or sometimes it is hard to understand why you would choose to use one feature over another. Over the years, a feature that I have seen many developers struggle with is when to choose to use an interface or to choose to use an abstract class. Both have there advantages and disadvantages and the correct time and place to use each. But how to we decide???
Both provide for reuse of common functionality between types. The most obvious difference right away is that interfaces provide no implementation for their functionality whereas abstract classes allow you to implement some “base” or “default” behavior and then have the ability to “override” this default behavior with the classes derived types if necessary.
This is all well and good and provides for great reuse of code and adheres to the DRY (Don’t Repeat Yourself) principle of software development. Abstract classes are great to use when you have an “is a” relationship.
For example: A golden retriever “is a” type of dog. So is a poodle. They both can bark, as all dogs can. However, you might want to state that the poodle park is significantly different than the “default” dog bark. Therefor, it could make sense for you to implement something as follows:
public abstract class Dog
{
public virtual void Bark()
{
Console.WriteLine("Base Class implementation of Bark");
}
}
public class GoldenRetriever : Dog
{
// the Bark method is inherited from the Dog class
}
public class Poodle : Dog
{
// here we are overriding the base functionality of Bark with our new implementation
// specific to the Poodle class
public override void Bark()
{
Console.WriteLine("Poodle's implementation of Bark");
}
}
// Add a list of dogs to a collection and call the bark method.
void Main()
{
var poodle = new Poodle();
var goldenRetriever = new GoldenRetriever();
var dogs = new List<Dog>();
dogs.Add(poodle);
dogs.Add(goldenRetriever);
foreach (var dog in dogs)
{
dog.Bark();
}
}
// Output will be:
// Poodle's implementation of Bark
// Base Class implementation of Bark
//
As you can see, this would be a great way to keep your code DRY and allow for the base class implementation be called when any of the types can just rely on the default Bark instead of a special case implementation. The classes like GoldenRetriever, Boxer, Lab could all could inherit the “default” (bass class) Bark at no charge just because they implement the Dog abstract class.
But I’m sure you already knew that.
You are here because you want to understand why you might want to choose an interface over an abstract class or vice versa. Well one reason you may want to choose an interface over an abstract class is when you don’t have or want to prevent a default implementation. This is usually because the types that are implementing the interface not related in an “is a” relationship. Actually, they don’t have to be related at all except for the fact that each type “is able” or has “the ablity” to do something or have something.
Now what the heck does that mean? Well, for example: A human is not a duck…and a duck is not a human. Pretty obvious. However, both a duck and a human have “the ability” to swim (given that the human passed his swimming lessons in 1st grade :) ). Also, since a duck is not a human or vice versa, this is not an “is a” realationship, but instead an “is able” relationship and we can use an interface to illustrate that:
// Create ISwimable interface
public interface ISwimable
{
public void Swim();
}
// Have Human implement ISwimable Interface
public class Human : ISwimable
public void Swim()
{
//Human's implementation of Swim
Console.WriteLine("I'm a human swimming!");
}
// Have Duck implement ISwimable interface
public class Duck: ISwimable
{
public void Swim()
{
// Duck's implementation of Swim
Console.WriteLine("Quack! Quack! I'm a Duck swimming!")
}
}
//Now they can both be used in places where you just need an object that has the ability "to swim"
public void ShowHowYouSwim(ISwimable somethingThatCanSwim)
{
somethingThatCanSwim.Swim();
}
public void Main()
{
var human = new Human();
var duck = new Duck();
var listOfThingsThatCanSwim = new List<ISwimable>();
listOfThingsThatCanSwim.Add(duck);
listOfThingsThatCanSwim.Add(human);
foreach (var something in listOfThingsThatCanSwim)
{
ShowHowYouSwim(something);
}
}
// So at runtime the correct implementation of something.Swim() will be called
// Output:
// Quack! Quack! I'm a Duck swimming!
// I'm a human swimming!
Using interfaces like the code above will allow you to pass an object into a method that “is able” to do something. The code doesn’t care how it does it…All it knows is that it can call the Swim method on that object and that object will know which behavior take at run-time based on its type.
Once again, this helps your code stay DRY so that you would not have to write multiple methods that are calling the object to preform the same core function (ShowHowHumanSwims(human), ShowHowDuckSwims(duck), etc.)
Using an interface here allows the calling methods to not have to worry about what type is which or how the behavior is implemented. It just knows that given the interface, each object will have to have implemented the Swim method so it is safe to call it in its own code and allow the behavior of the Swim method be handled within its own class.
Summary:
So my main rule of thumb is use an abstract class when you want to implement a “default” functionality for a class hierarchy or/and the classes or types you are working with share a “is a” relationship (ex. poodle “is a” type of dog).
On the other hand use an interface when you do not have an “is a” relationship but have types that share “the ability” to do something or have something (ex. Duck “is not” a human. However, duck and human share “the ability” to swim).
Another difference to note between abstract classes and interfaces is that a class can implement one to many interfaces but a class can only inherit from ONE abstract class (or any class for that matter). Yes, you can nest classes and have an inheritance hierarchy (which many programs do and should have) but you cannot inherit two classes in one derived class definition (this rule applies to C#. In some other languages you are able to do this, usually only because of the lack of interfaces in these languages).
Also remember when using interfaces to adhere to the Interface Segregation Principle (ISP). ISP states that no client should be forced to depend on methods it does not use. For this reason interfaces should be focused on specific tasks and are usually very small (ex. IDisposable, IComparable ).
Another tip is if you are developing small, concise bits of functionality, use interfaces. If you are designing large functional units, use an abstract class.
Hope this clears things up for some people!
Also if you can think of any better examples or want to point something out, please do so in the comments below!
Static Methods:
Benefits of Static Methods:
More convenient to import versus module-level functions since each method does not have to be specially imported
@staticmethod
def some_static_method(*args, **kwds):
pass
Class Methods:
These are created with classmethod in-built function.
@classmethod
def some_class_method(cls, *args, **kwds):
pass
Really depends on your requirement, although lately I have seen a trend for classes with at least one bare constructor defined.
The upside of posting your parameters in via constructor is that you know those values can be relied on after instantiation. The downside is that you'll need to put more work in with any library that expects to be able to create objects with a bare constructor.
My personal preference is to go with a bare constructor and set any properties as part of the declaration.
Person p=new Person()
{
Name = "Han Solo",
Age = 39
};
This gets around the "class lacks bare constructor" problem, plus reduces maintenance ( I can set more things without changing the constructor ).
You should make your audioSounds and minTime members static:
public static List<AudioSource> audioSounds = new List<AudioSource>();
public static double minTime = 0.5;
But I would consider using singleton objects instead of static members instead:
public class SoundManager : MonoBehaviour
{
public List<AudioSource> audioSounds = new List<AudioSource>();
public double minTime = 0.5;
public static SoundManager Instance { get; private set; }
void Awake()
{
Instance = this;
}
public void playSound(AudioClip sourceSound, Vector3 objectPosition, int volume, float audioPitch, int dopplerLevel)
{
bool playsound = false;
foreach (AudioSource sound in audioSounds) // Loop through List with foreach
{
if (sourceSound.name != sound.name && sound.time <= minTime)
{
playsound = true;
}
}
if(playsound) {
AudioSource.PlayClipAtPoint(sourceSound, objectPosition);
}
}
}
Update from September 2020:
Six years later, it is still one of my most upvoted answers on StackOverflow, so I feel obligated to add: singleton is a pattern that creates a lot of problems down the road, and personally, I consider it to be an anti-pattern. It can be accessed from anywhere, and using singletons for different game systems creates a spaghetti of invisible dependencies between different parts of your project.
If you're just learning to program, using singletons is OK for now. But please, consider reading about Dependency Injection, Inversion of Control and other architectural patterns. At least file it under "stuff I will learn later". This may sound as an overkill when you first learn about them, but a proper architecture can become a life-saver on middle and big projects.
Cohesion is an indication of how related and focused the responsibilities of an software element are.
Coupling refers to how strongly a software element is connected to other elements.
The software element could be class, package, component, subsystem or a system. And while designing the systems it is recommended to have software elements that have High cohesion and support Low coupling.
Low cohesion results in monolithic classes that are difficult to maintain, understand and reduces re-usablity. Similarly High Coupling results in classes that are tightly coupled and changes tend not be non-local, difficult to change and reduces the reuse.
We can take a hypothetical scenario where we are designing an typical monitor-able ConnectionPool
with the following requirements. Note that, it might look too much for a simple class like ConnectionPool
but the basic intent is just to demonstrate low coupling and high cohesion with some simple example and I think should help.
With low cohesion we could design a ConnectionPool
class by forcefully stuffing all this functionality/responsibilities into a single class as below. We can see that this single class is responsible for connection management, interacting with database as well maintaining connection stats.
With high cohesion we can assign these responsibility across the classes and make it more maintainable and reusable.
To demonstrate Low coupling we will continue with the high cohesion ConnectionPool
diagram above. If we look at the above diagram although it supports high cohesion, the ConnectionPool
is tightly coupled with ConnectionStatistics
class and PersistentStore
it interacts with them directly. Instead to reduce the coupling we could introduce a ConnectionListener
interface and let these two classes implement the interface and let them register with ConnectionPool
class. And the ConnectionPool
will iterate through these listeners and notify them of connection get and release events and allows less coupling.
Note/Word or Caution: For this simple scenario it may look like an overkill but if we imagine a real-time scenario where our application needs to interact with multiple third party services to complete a transaction: Directly coupling our code with the third party services would mean that any changes in the third party service could result in changes to our code at multiple places, instead we could have Facade
that interacts with these multiple services internally and any changes to the services become local to the Facade
and enforce low coupling with the third party services.
A nice cheat sheet (http://loufranco.com/wp-content/uploads/2012/11/cheatsheet.pdf):
It covers:
And provides a few samples.
Computer c= new Computer()
Here an object is created from the Computer
class. A reference named c allows the programmer to access the object.
This is not exactly an answer, rather sharing my findings, and hopefully getting some critical argument for/against it, as specifically I am not aware how efficient it is.
I recently had a need to do this for my project. I did this using Object.assign
, more precisely it is done something like this:Object.assign(new Person(...), anObjectLikePerson)
.
Here is link to my JSFiddle, and also the main part of the code:
function Person(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
this.getFullName = function() {
return this.lastName + ' ' + this.firstName;
}
}
var persons = [{
lastName: "Freeman",
firstName: "Gordon"
}, {
lastName: "Smith",
firstName: "John"
}];
var stronglyTypedPersons = [];
for (var i = 0; i < persons.length; i++) {
stronglyTypedPersons.push(Object.assign(new Person("", ""), persons[i]));
}
In addition to the other answers to this question, using an anonymous namespace can also improve performance. As symbols within the namespace do not need any external linkage, the compiler is freer to perform aggressive optimization of the code within the namespace. For example, a function which is called multiple times once in a loop can be inlined without any impact on the code size.
For example, on my system the following code takes around 70% of the run time if the anonymous namespace is used (x86-64 gcc-4.6.3 and -O2; note that the extra code in add_val makes the compiler not want to include it twice).
#include <iostream>
namespace {
double a;
void b(double x)
{
a -= x;
}
void add_val(double x)
{
a += x;
if(x==0.01) b(0);
if(x==0.02) b(0.6);
if(x==0.03) b(-0.1);
if(x==0.04) b(0.4);
}
}
int main()
{
a = 0;
for(int i=0; i<1000000000; ++i)
{
add_val(i*1e-10);
}
std::cout << a << '\n';
return 0;
}
Better late than never - if you're looking for unnecessary clutter or overhead then it's hard to beat the following in terms of least code/fast execution at the same time.
Data class:
public class MyData {
int id;
boolean relevant;
String name;
float value;
}
Comparator:
public class MultiFieldComparator implements Comparator<MyData> {
@Override
public int compare(MyData dataA, MyData dataB) {
int result;
if((result = Integer.compare(dataA.id, dataB.id)) == 0 &&
(result = Boolean.compare(dataA.relevant, dataB.relevant)) == 0 &&
(result = dataA.name.compareTo(dataB.name)) == 0)
result = Float.compare(dataA.value, dataB.value);
return result;
}
}
If you are just looking to sort a collection by a custom order then the following is even cleaner:
myDataList.sort((dataA, dataB) -> {
int result;
if((result = Integer.compare(dataA.id, dataB.id)) == 0 &&
(result = Boolean.compare(dataA.relevant, dataB.relevant)) == 0 &&
(result = dataA.name.compareTo(dataB.name)) == 0)
result = Float.compare(dataA.value, dataB.value);
return result;
});
class Foo(object):
bar = 1
def bah(self):
print Foo.bar
f = Foo()
f.bah()
When do you choose functional programming over object oriented?
When you anticipate a different kind of software evolution:
Object-oriented languages are good when you have a fixed set of operations on things, and as your code evolves, you primarily add new things. This can be accomplished by adding new classes which implement existing methods, and the existing classes are left alone.
Functional languages are good when you have a fixed set of things, and as your code evolves, you primarily add new operations on existing things. This can be accomplished by adding new functions which compute with existing data types, and the existing functions are left alone.
When evolution goes the wrong way, you have problems:
Adding a new operation to an object-oriented program may require editing many class definitions to add a new method.
Adding a new kind of thing to a functional program may require editing many function definitions to add a new case.
This problem has been well known for many years; in 1998, Phil Wadler dubbed it the "expression problem". Although some researchers think that the expression problem can be addressed with such language features as mixins, a widely accepted solution has yet to hit the mainstream.
What are the typical problem definitions where functional programming is a better choice?
Functional languages excel at manipulating symbolic data in tree form. A favorite example is compilers, where source and intermediate languages change seldom (mostly the same things), but compiler writers are always adding new translations and code improvements or optimizations (new operations on things). Compilation and translation more generally are "killer apps" for functional languages.
Strings do have a length method: __len__()
The protocol in Python is to implement this method on objects which have a length and use the built-in len()
function, which calls it for you, similar to the way you would implement __iter__()
and use the built-in iter()
function (or have the method called behind the scenes for you) on objects which are iterable.
See Emulating container types for more information.
Here's a good read on the subject of protocols in Python: Python and the Principle of Least Astonishment
First there is an elevator class. It has a direction (up, down, stand, maintenance), a current floor and a list of floor requests sorted in the direction. It receives request from this elevator.
Then there is a bank. It contains the elevators and receives the requests from the floors. These are scheduled to all active elevators (not in maintenance).
The scheduling will be like:
Each elevator has a set of states.
There are additional signals:
EDIT: Some elevators don't start at bottom/first_floor esp. in case of skyscrapers.
min_floor & max_floor are two additional attributes for Elevator.
I can't believe, except for one guy no one has used the code to explain this, let me give it a shot too!
// Design Class
class HumanClass {
var name:String
init(name:String) {
self.name = name
}
}
var humanClassObject1 = HumanClass(name: "Rehan")
Now the left side i.e: "humanClassObject1" is the object and the right side i.e: HumanClass(name: "Rehan") is the instance of this object.
var humanClassObject2 = HumanClass(name: "Ahmad") // again object on left and it's instance on the right.
So basically, instance contains the specific values for that object and objects contains the memory location (at run-time).
Remember the famous statement "object reference not set to an instance of an object", this means that non-initialised objects don't have any instance. In some programming languages like swift the compiler will not allow you to even design a class that don't have any way to initialise all it's members (variable eg: name, age e.t.c), but in some language you are allowed to do this:
// Design Class
class HumanClass {
var name:String // See we don't have any way to initialise name property.
}
And the error will only be shown at run time when you try to do something like this:
var myClass = HumanClass()
print(myClass.name) // will give, object reference not set to an instance of the object.
This error indicates that, the specific values (for variables\property) is the "INSTANCE" as i tried to explain this above! And the object i.e: "myClass" contains the memory location (at run-time).
It's important to point out to readers stumbling upon this question when researching the subject in a broader fashion that the accepted answer's procedure is not required in the case you just want to split your project into files. It's only needed when you need multiple implementations of single classes. If your implementation per class is one, just one header file for each is enough.
Hence, from the accepted answer's example only this part is needed:
#ifndef MYHEADER_H
#define MYHEADER_H
//Class goes here, full declaration AND implementation
#endif
The #ifndef etc. preprocessor definitions allow it to be used multiple times.
PS. The topic becomes clearer once you realize C/C++ is 'dumb' and #include is merely a way to say "dump this text at this spot".
Specific to C#, I found "Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries" to have lots of good information on the logic of naming.
As far as finding those more specific words though, I often use a thesaurus and jump through related words to try and find a good one. I try not to spend to much time with it though, as I progress through development I come up with better names, or sometimes realize that SuchAndSuchManager
should really be broken up into multiple classes, and then the name of that deprecated class becomes a non-issue.
Most modern languages are in varying degree both imperative and functional but to better understand functional programming, it will be best to take an example of pure functional language like Haskell in contrast of imperative code in not so functional language like java/C#. I believe it is always easy to explain by example, so below is one.
Functional programming: calculate factorial of n i.e n! i.e n x (n-1) x (n-2) x ...x 2 X 1
-- | Haskell comment goes like
-- | below 2 lines is code to calculate factorial and 3rd is it's execution
factorial 0 = 1
factorial n = n * factorial (n - 1)
factorial 3
-- | for brevity let's call factorial as f; And x => y shows order execution left to right
-- | above executes as := f(3) as 3 x f(2) => f(2) as 2 x f(1) => f(1) as 1 x f(0) => f(0) as 1
-- | 3 x (2 x (1 x (1)) = 6
Notice that Haskel allows function overloading to the level of argument value. Now below is example of imperative code in increasing degree of imperativeness:
//somewhat functional way
function factorial(n) {
if(n < 1) {
return 1;
}
return n * factorial(n-1);
}
factorial(3);
//somewhat more imperative way
function imperativeFactor(n) {
int f = 1;
for(int i = 1; i <= n; i++) {
f = f * i;
}
return f;
}
This read can be a good reference to understand that how imperative code focus more on how part, state of machine (i in for loop), order of execution, flow control.
The later example can be seen as java/C# lang code roughly and first part as limitation of the language itself in contrast of Haskell to overload the function by value (zero) and hence can be said it is not purist functional language, on the other hand you can say it support functional prog. to some extent.
Disclosure: none of the above code is tested/executed but hopefully should be good enough to convey the concept; also I would appreciate comments for any such correction :)
A. Static Method:
Class.method = function () { /* code */ }
method()
here is a function property added to an another function (here Class).Class.method();
new Class()
) for accessing the method(). So you could call it as a static method.B. Prototype Method (Shared across all the instances):
Class.prototype.method = function () { /* code using this.values */ }
method()
here is a function property added to an another function protype (here Class.prototype).new Class()
).Class
C. Class Method (Each instance has its own copy):
function Class () {
this.method = function () { /* do something with the private members */};
}
method()
here is a method defined inside an another function (here Class).Class.method();
new Class()
) for the method() access.new Class()
).Example:
function Class() {
var str = "Constructor method"; // private variable
this.method = function () { console.log(str); };
}
Class.prototype.method = function() { console.log("Prototype method"); };
Class.method = function() { console.log("Static method"); };
new Class().method(); // Constructor method
// Bcos Constructor method() has more priority over the Prototype method()
// Bcos of the existence of the Constructor method(), the Prototype method
// will not be looked up. But you call it by explicity, if you want.
// Using instance
new Class().constructor.prototype.method(); // Prototype method
// Using class name
Class.prototype.method(); // Prototype method
// Access the static method by class name
Class.method(); // Static method
Answer 1 : Yes it called upcasting but the way you do it is not modern way. Upcasting can be performed implicitly you don't need any conversion. So just writing Employee emp = mgr; is enough for upcasting.
Answer 2 : If you create object of Manager class we can say that manager is an employee. Because class Manager : Employee depicts Is-A relationship between Employee Class and Manager Class. So we can say that every manager is an employee.
But if we create object of Employee class we can not say that this employee is manager because class Employee is a class which is not inheriting any other class. So you can not directly downcast that Employee Class object to Manager Class object.
So answer is, if you want to downcast from Employee Class object to Manager Class object, first you must have object of Manager Class first then you can upcast it and then you can downcast it.
There are tree ways methods and properties are implemented on function or class objects, and on they instances.
Foo.method()
or Foo.prop
. Those are static methods or propertiesFoo.prototype.method()
or Foo.prototype.prop
. When created, the instances will inherit those object via the prototype witch is {method:function(){...}, prop:...}
. So the foo object will receive, as prototype, a copy of the Foo.prototype object.foo={method:function(){...}, prop:...}
The this
keyword will represent and act differently according to the context. In a static method, it will represent the class itself (witch is after all an instance of Function : class Foo {}
is quite equivalent to let Foo = new Function({})
With ECMAScript 2015, that seems well implemented today, it is clearer to see the difference between class (static) methods and properties, instance methods and properties and own methods ans properties. You can thus create three method or properties having the same name, but being different because they apply to different objects, the this
keyword, in methods, will apply to, respectively, the class object itself and the instance object, by the prototype or by its own.
class Foo {
constructor(){super();}
static prop = "I am static" // see 1.
static method(str) {alert("static method"+str+" :"+this.prop)} // see 1.
prop="I am of an instance"; // see 2.
method(str) {alert("instance method"+str+" : "+this.prop)} // see 2.
}
var foo= new Foo();
foo.prop = "I am of own"; // see 3.
foo.func = function(str){alert("own method" + str + this.prop)} // see 3.
If you need something from super's __init__
to be done in addition to what is being done in the current class's __init__,
you must call it yourself, since that will not happen automatically. But if you don't need anything from super's __init__,
no need to call it. Example:
>>> class C(object):
def __init__(self):
self.b = 1
>>> class D(C):
def __init__(self):
super().__init__() # in Python 2 use super(D, self).__init__()
self.a = 1
>>> class E(C):
def __init__(self):
self.a = 1
>>> d = D()
>>> d.a
1
>>> d.b # This works because of the call to super's init
1
>>> e = E()
>>> e.a
1
>>> e.b # This is going to fail since nothing in E initializes b...
Traceback (most recent call last):
File "<pyshell#70>", line 1, in <module>
e.b # This is going to fail since nothing in E initializes b...
AttributeError: 'E' object has no attribute 'b'
__del__
is the same way, (but be wary of relying on __del__
for finalization - consider doing it via the with statement instead).
I rarely use __new__.
I do all the initialization in __init__.
I think there is a much better approach, that allows for solid type-safety and scalability.
First declare interfaces that you want to implement on your target class:
interface IBar {
doBarThings(): void;
}
interface IBazz {
doBazzThings(): void;
}
class Foo implements IBar, IBazz {}
Now we have to add the implementation to the Foo
class. We can use class mixins that also implements these interfaces:
class Base {}
type Constructor<I = Base> = new (...args: any[]) => I;
function Bar<T extends Constructor>(constructor: T = Base as any) {
return class extends constructor implements IBar {
public doBarThings() {
console.log("Do bar!");
}
};
}
function Bazz<T extends Constructor>(constructor: T = Base as any) {
return class extends constructor implements IBazz {
public doBazzThings() {
console.log("Do bazz!");
}
};
}
Extend the Foo
class with the class mixins:
class Foo extends Bar(Bazz()) implements IBar, IBazz {
public doBarThings() {
super.doBarThings();
console.log("Override mixin");
}
}
const foo = new Foo();
foo.doBazzThings(); // Do bazz!
foo.doBarThings(); // Do bar! // Override mixin
If you want to ensure they all get called, use super
at all levels.
When I am trying to share behavior between 2 closely related classes, I create an abstract class that holds the common behavior and serves as a parent to both classes.
When I am trying to define a Type, a list of methods that a user of my object can reliably call upon, then I create an interface.
For example, I would never create an abstract class with 1 concrete subclass because abstract classes are about sharing behavior. But I might very well create an interface with only one implementation. The user of my code won't know that there is only one implementation. Indeed, in a future release there may be several implementations, all of which are subclasses of some new abstract class that didn't even exist when I created the interface.
That might have seemed a bit too bookish too (though I have never seen it put that way anywhere that I recall). If the interviewer (or the OP) really wanted more of my personal experience on that, I would have been ready with anecdotes of an interface has evolved out of necessity and visa versa.
One more thing. Java 8 now allows you to put default code into an interface, further blurring the line between interfaces and abstract classes. But from what I have seen, that feature is overused even by the makers of the Java core libraries. That feature was added, and rightly so, to make it possible to extend an interface without creating binary incompatibility. But if you are making a brand new Type by defining an interface, then the interface should be JUST an interface. If you want to also provide common code, then by all means make a helper class (abstract or concrete). Don't be cluttering your interface from the start with functionality that you may want to change.
You can also create a free function in a namespace:
In BitParser.h
namespace BitParser
{
bool getBitAt(int buffer, int bitIndex);
}
In BitParser.cpp
namespace BitParser
{
bool getBitAt(int buffer, int bitIndex)
{
//get the bit :)
}
}
In general this would be the preferred way to write the code. When there's no need for an object don't use a class.
I'd like to add one more difference which makes sense. For example, you have a framework with thousands of lines of code. Now if you want to add a new feature throughout the code using a method enhanceUI(), then it's better to add that method in abstract class rather in interface. Because, if you add this method in an interface then you should implement it in all the implemented class but it's not the case if you add the method in abstract class.
You could pass a Class<T>
in.
private void foo(Class<?> cls) {
if (cls == String.class) { ... }
else if (cls == int.class) { ... }
}
private void bar() {
foo(String.class);
}
Update: the OOP way depends on the functional requirement. Best bet would be an interface defining foo()
and two concrete implementations implementing foo()
and then just call foo()
on the implementation you've at hand. Another way may be a Map<Class<?>, Action>
which you could call by actions.get(cls)
. This is easily to be combined with an interface and concrete implementations: actions.get(cls).foo()
.
This will get you the hours, minutes and second. hey presto.
select
to_char(CREATION_TIME,'RRRR') year,
to_char(CREATION_TIME,'MM') MONTH,
to_char(CREATION_TIME,'DD') DAY,
to_char(CREATION_TIME,'HH:MM:SS') TIME,
sum(bytes) Bytes
from
v$datafile
group by
to_char(CREATION_TIME,'RRRR'),
to_char(CREATION_TIME,'MM'),
to_char(CREATION_TIME,'DD'),
to_char(CREATION_TIME,'HH:MM:SS')
ORDER BY 1, 2;
Aergistal's answer works, but I found that converting to mp4 can make some m3u8 videos broken. If you are stuck with this problem, try to convert them to mkv, and convert them to mp4 later.
As ping
works, but telnet
to port 80
does not, the HTTP port 80
is closed on your machine. I assume that your browser's HTTP connection goes through a proxy (as browsing works, how else would you read stackoverflow?).
You need to add some code to your python program, that handles the proxy, like described here:
<script>
function seetext(x){
x.type = "text";
}
function seeasterisk(x){
x.type = "password";
}
</script>
<body>
<img onmouseover="seetext(a)" onmouseout="seeasterisk(a)" border="0" src="smiley.gif" alt="Smiley" width="32" height="32">
<input id = "a" type = "password"/>
</body>
Try this see if it works
Another solution, based on scroll listener. Initial conditions are the same as in Sevastyan answer
RecyclerView recyclerView;
TextView tvTitle; //sticky header view
//... onCreate, initialize, etc...
public void bindList(List<Item> items) { //All data in adapter. Item - just interface for different item types
adapter = new YourAdapter(items);
recyclerView.setAdapter(adapter);
StickyHeaderViewManager<HeaderItem> stickyHeaderViewManager = new StickyHeaderViewManager<>(
tvTitle,
recyclerView,
HeaderItem.class, //HeaderItem - subclass of Item, used to detect headers in list
data -> { // bind function for sticky header view
tvTitle.setText(data.getTitle());
});
stickyHeaderViewManager.attach(items);
}
Layout for ViewHolder and sticky header.
item_header.xml
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/tv_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
Layout for RecyclerView
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<!--it can be any view, but order important, draw over recyclerView-->
<include
layout="@layout/item_header"/>
</FrameLayout>
Class for HeaderItem.
public class HeaderItem implements Item {
private String title;
public HeaderItem(String title) {
this.title = title;
}
public String getTitle() {
return title;
}
}
It's all use. The implementation of the adapter, ViewHolder and other things, is not interesting for us.
public class StickyHeaderViewManager<T> {
@Nonnull
private View headerView;
@Nonnull
private RecyclerView recyclerView;
@Nonnull
private StickyHeaderViewWrapper<T> viewWrapper;
@Nonnull
private Class<T> headerDataClass;
private List<?> items;
public StickyHeaderViewManager(@Nonnull View headerView,
@Nonnull RecyclerView recyclerView,
@Nonnull Class<T> headerDataClass,
@Nonnull StickyHeaderViewWrapper<T> viewWrapper) {
this.headerView = headerView;
this.viewWrapper = viewWrapper;
this.recyclerView = recyclerView;
this.headerDataClass = headerDataClass;
}
public void attach(@Nonnull List<?> items) {
this.items = items;
if (ViewCompat.isLaidOut(headerView)) {
bindHeader(recyclerView);
} else {
headerView.post(() -> bindHeader(recyclerView));
}
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
bindHeader(recyclerView);
}
});
}
private void bindHeader(RecyclerView recyclerView) {
if (items.isEmpty()) {
headerView.setVisibility(View.GONE);
return;
} else {
headerView.setVisibility(View.VISIBLE);
}
View topView = recyclerView.getChildAt(0);
if (topView == null) {
return;
}
int topPosition = recyclerView.getChildAdapterPosition(topView);
if (!isValidPosition(topPosition)) {
return;
}
if (topPosition == 0 && topView.getTop() == recyclerView.getTop()) {
headerView.setVisibility(View.GONE);
return;
} else {
headerView.setVisibility(View.VISIBLE);
}
T stickyItem;
Object firstItem = items.get(topPosition);
if (headerDataClass.isInstance(firstItem)) {
stickyItem = headerDataClass.cast(firstItem);
headerView.setTranslationY(0);
} else {
stickyItem = findNearestHeader(topPosition);
int secondPosition = topPosition + 1;
if (isValidPosition(secondPosition)) {
Object secondItem = items.get(secondPosition);
if (headerDataClass.isInstance(secondItem)) {
View secondView = recyclerView.getChildAt(1);
if (secondView != null) {
moveViewFor(secondView);
}
} else {
headerView.setTranslationY(0);
}
}
}
if (stickyItem != null) {
viewWrapper.bindView(stickyItem);
}
}
private void moveViewFor(View secondView) {
if (secondView.getTop() <= headerView.getBottom()) {
headerView.setTranslationY(secondView.getTop() - headerView.getHeight());
} else {
headerView.setTranslationY(0);
}
}
private T findNearestHeader(int position) {
for (int i = position; position >= 0; i--) {
Object item = items.get(i);
if (headerDataClass.isInstance(item)) {
return headerDataClass.cast(item);
}
}
return null;
}
private boolean isValidPosition(int position) {
return !(position == RecyclerView.NO_POSITION || position >= items.size());
}
}
Interface for bind header view.
public interface StickyHeaderViewWrapper<T> {
void bindView(T data);
}
#define BITS_SIZE 8
int
reverseBits ( int a )
{
int rev = 0;
int i;
/* scans each bit of the input number*/
for ( i = 0; i < BITS_SIZE - 1; i++ )
{
/* checks if the bit is 1 */
if ( a & ( 1 << i ) )
{
/* shifts the bit 1, starting from the MSB to LSB
* to build the reverse number
*/
rev |= 1 << ( BITS_SIZE - 1 ) - i;
}
}
return rev;
}
6.5.5 Multiplicative operators
...
6 When integers are divided, the result of the/
operator is the algebraic quotient with any fractional part discarded.105) If the quotienta/b
is representable, the expression(a/b)*b + a%b
shall equala
; otherwise, the behavior of botha/b
anda%b
is unde?ned.
105) This is often called ‘‘truncation toward zero’’.
Dividing an integer by an integer gives an integer result. 1/2 yields 0; assigning this result to a floating-point variable gives 0.0. To get a floating-point result, at least one of the operands must be a floating-point type. b = a / 350.0f;
should give you the result you want.
just fetch specific node data and its working perfect for me
mFirebaseInstance.getReference("yourNodeName").getRef().addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
Log.e(TAG, "======="+postSnapshot.child("email").getValue());
Log.e(TAG, "======="+postSnapshot.child("name").getValue());
}
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.e(TAG, "Failed to read app title value.", error.toException());
}
});
Use prepared statements. Those keep the data and syntax apart, which removes the need for escaping MySQL data. See e.g. this tutorial.
For someone who needs quick reference of C# Escape Sequences that can be used in string
literals:
\t Horizontal tab (ASCII code value: 9)
\n Line feed (ASCII code value: 10)
\r Carriage return (ASCII code value: 13)
\' Single quotation mark
\" Double quotation mark
\\ Backslash
\? Literal question mark
\x12 ASCII character in hexadecimal notation (e.g. for 0x12)
\x1234 Unicode character in hexadecimal notation (e.g. for 0x1234)
It's worth mentioning that these (in most cases) are universal codes. So \t is 9 and \n is 10 char value on Windows and Linux. But newline sequence is not universal. On Windows it's \n\r and on Linux it's just \n. That's why it's best to use Environment.Newline
which gets adjusted to current OS settings. With .Net Core it gets really important.
Use split()
let mut split = "some string 123 ffd".split("123");
This gives an iterator, which you can loop over, or collect()
into a vector.
for s in split {
println!("{}", s)
}
let vec = split.collect::<Vec<&str>>();
// OR
let vec: Vec<&str> = split.collect();
I believe you are using the
echo Text >> Example.txt
function?
If so the answer would be simply adding a "." (Dot) directly after the echo with nothing else there.
Example:
echo Blah
echo Blah 2
echo. #New line is added
echo Next Blah
Try it like this:
Sub testIt()
Dim r As Long, endRow as Long, pasteRowIndex As Long
endRow = 10 ' of course it's best to retrieve the last used row number via a function
pasteRowIndex = 1
For r = 1 To endRow 'Loop through sheet1 and search for your criteria
If Cells(r, Columns("B").Column).Value = "YourCriteria" Then 'Found
'Copy the current row
Rows(r).Select
Selection.Copy
'Switch to the sheet where you want to paste it & paste
Sheets("Sheet2").Select
Rows(pasteRowIndex).Select
ActiveSheet.Paste
'Next time you find a match, it will be pasted in a new row
pasteRowIndex = pasteRowIndex + 1
'Switch back to your table & continue to search for your criteria
Sheets("Sheet1").Select
End If
Next r
End Sub
Abstraction is one of the many benefits of Data Encapsulation. We can also say Data Encapsulation is one way to implement Abstraction.
I had the same problem, tnsnames.ora
worked fine for all other tools but SQL Developer would not use it. I tried all the suggestions on the web I could find, including the solutions on the link provided here.
Nothing worked.
It turns out that the database was caching backup copies of tnsnames.ora
like tnsnames.ora.bk2
, tnsnames09042811AM4501.bak
, tnsnames.ora.bk
etc. These files were not readable by the average user.
I suspect sqldeveloper is pattern matching for the name and it was trying to read one of these backup copies and couldn't. So it just fails gracefully and shows nothing in drop down list.
The solution is to make all the files readable or delete or move the backup copies out of the Admin directory.
An established connection was aborted by the software in your host machine
That is a boiler-plate error message, it comes out of Windows. The underlying error code is WSAECONNABORTED. Which really doesn't mean more than "connection was aborted". You have to be a bit careful about the "your host machine" part of the phrase. In the vast majority of Windows application programs, it is indeed the host that the desktop app is connected to that aborted the connection. Usually a server somewhere else.
The roles are reversed however when you implement your own server. Now you need to read the error message as "aborted by the application at the other end of the wire". Which is of course not uncommon when you implement a server, client programs that use your server are not unlikely to abort a connection for whatever reason. It can mean that a fire-wall or a proxy terminated the connection but that's not very likely since they typically would not allow the connection to be established in the first place.
You don't really know why a connection was aborted unless you have insight what is going on at the other end of the wire. That's of course hard to come by. If your server is reachable through the Internet then don't discount the possibility that you are being probed by a port scanner. Or your customers, looking for a game cheat.
To get the whole database structure as a set of CREATE TABLE statements, use mysqldump:
mysqldump database_name --compact --no-data
For single tables, add the table name after db name in mysqldump. You get the same results with SQL and SHOW CREATE TABLE:
SHOW CREATE TABLE table;
Or DESCRIBE if you prefer a column listing:
DESCRIBE table;
With my current reputation I have no ability to comment, so I choose answer referencing comments for sample code in reply by Prashant Gaur (thanks, Gaur - this was helpful!) - his sample is for python2, since python3 has no
unicodemethod.
The replacement below for function
get_prep_value(self, value):should work with Django running with python3 (I'll use this code soon - yet not tested). Note, though, that I'm passing
encoding='utf-8', errors='ignore'parameters to
decode()and
unicode() methods. Encoding should match your Django settings.py configuration and passing
errors='ignore'is optional (and may result in silent data loss instead of exception whith misconfigured django in rare cases).
import sys ... def get_prep_value(self, value): if value is None: return value if sys.version_info[0] >= 3: if isinstance(out_data, type(b'')): return value.decode(encoding='utf-8', errors='ignore') else: if isinstance(out_data, type(b'')): return unicode(value, encoding='utf-8', errors='ignore') return str(value) ...
I ran into this issue and resolved it by removing the width styling I had used on the SVG:
.svg-div img {
width: 200px; /* removed this */
height: auto;
}
I've had the same problem, my fragments were pages of a ViewPager. The reason it was happening is that I was using child fragment manager rather than the activity support fragment manager when instantiating FragmentPagerAdapter.
There are no "usernames" in Git.
When creating a commit with Git it uses the configuration values of user.name
(the real name) and user.email
(email address). Those config values can be overridden on the console by setting and exporting the environment variables GIT_{COMMITTER,AUTHOR}_{NAME,EMAIL}
.
Git doesn't know anything about github's users, because github is not part of Git. So you're only left with an API call to github (I guess you could do that from the command line with a little scripting.)
Updated Answer:
DynamoDB allows for specification of secondary indexes to aid in this sort of query. Secondary indexes can either be global, meaning that the index spans the whole table across hash keys, or local meaning that the index would exist within each hash key partition, thus requiring the hash key to also be specified when making the query.
For the use case in this question, you would want to use a global secondary index on the "CreatedAt" field.
For more on DynamoDB secondary indexes see the secondary index documentation
Original Answer:
DynamoDB does not allow indexed lookups on the range key only. The hash key is required such that the service knows which partition to look in to find the data.
You can of course perform a scan operation to filter by the date value, however this would require a full table scan, so it is not ideal.
If you need to perform an indexed lookup of records by time across multiple primary keys, DynamoDB might not be the ideal service for you to use, or you might need to utilize a separate table (either in DynamoDB or a relational store) to store item metadata that you can perform an indexed lookup against.
print all folders name where batch script file is kept
for /d %%d in (*.*) do (
set test=%%d
echo !test!
)
pause
This worked for me & thought of sharing...
find ./ -type f -name "*" -not -name "*.o" -exec sh -c '
case "$(head -n 1 "$1")" in
?ELF*) exit 0;;
MZ*) exit 0;;
#!*/ocamlrun*)exit0;;
esac
exit 1
' sh {} \; -print
Fail module works great! Thanks.
I had to define my fact before checking it, otherwise I'd get an undefined variable error.
And I had issues when doing setting the fact with quotes and without spaces.
This worked:
set_fact: flag="failed"
This threw errors:
set_fact: flag = failed
Just for the fun, I'm offering an alternative solution using jOOQ and Java 8. Instead of using jOOQ, you could be using any other API that maps JDBC ResultSet
to List
, such as Spring JDBC or Apache DbUtils, or write your own ResultSetIterator
:
List<Object> list =
DSL.using(connection)
.fetch("SELECT col1, col2, col3, ...")
.stream()
.flatMap(r -> Arrays.stream(r.intoArray()))
.collect(Collectors.toList());
List<Object> list =
DSL.using(connection)
.fetch("SELECT col1, col2, col3, ...")
.stream()
.flatMap(Record::intoStream)
.collect(Collectors.toList());
(Disclaimer, I work for the company behind jOOQ)
In Java 9, you can simply write: Map.entry(key, value)
to create an immutable pair.
Note: this method does not allow keys or values to be null. If you want to allow null values, for example, you'd want to change this to: Map.entry(key, Optional.ofNullable(value))
.
In Java 8, you can use the more general-purpose javafx.util.Pair
to create an immutable, serializable pair. This class does allow null keys and null values. (In Java 9, this class is included in the javafx.base
module). EDIT: As of Java 11, JavaFX has been decoupled from the JDK, so you'd need the additional maven artifact org.openjfx:javafx-base.
In Java 6 and up, you can use the more verbose AbstractMap.SimpleImmutableEntry
for an immutable pair, or AbstractMap.SimpleEntry
for a pair whose value can be changed. These classes also allow null keys and null values, and are serializable.
If you're writing for Android, just use Pair.create(key, value)
to create an immutable pair.
Apache Commons Lang
provides the helpful Pair.of(key, value)
to create an immutable, comparable, serializable pair.
If you're using pairs that contain primitives, Eclipse Collections provides some very efficient primitive pair classes that will avoid all the inefficient auto-boxing and auto-unboxing.
For instance, you could use PrimitiveTuples.pair(int, int)
to create an IntIntPair
, or PrimitiveTuples.pair(float, long)
to create a FloatLongPair
.
Using Project Lombok, you can create an immutable pair class simply by writing:
@Value
public class Pair<K, V> {
K key;
V value;
}
Lombok will fill in the constructor, getters, equals()
, hashCode()
, and toString()
methods for you automatically in the generated bytecode. If you want a static factory method instead of a constructor, e.g., a Pair.of(k, v)
, simply change the annotation to: @Value(staticConstructor = "of")
.
If none of the above solutions float your boat, you can simply copy and paste the following code (which, unlike the class listed in the accepted answer, guards against NullPointerExceptions):
import java.util.Objects;
public class Pair<K, V> {
public final K key;
public final V value;
public Pair(K key, V value) {
this.key = key;
this.value = value;
}
public boolean equals(Object o) {
return o instanceof Pair && Objects.equals(key, ((Pair<?,?>)o).key) && Objects.equals(value, ((Pair<?,?>)o).value);
}
public int hashCode() {
return 31 * Objects.hashCode(key) + Objects.hashCode(value);
}
public String toString() {
return key + "=" + value;
}
}
Try the vim-way:
ex -s +"g/foo/d" -cwq file.txt
You forgot to define the default value for left
so it doesn't know how to animate.
.test {
left: 0;
transition:left 1s linear;
}
See here: http://jsfiddle.net/shomz/yFy5n/5/
You can also consider contract classes implemented with the NVI (Non Virtual Interface Pattern). For instance:
struct Contract1 : boost::noncopyable
{
virtual ~Contract1();
void f(Parameters p) {
assert(checkFPreconditions(p)&&"Contract1::f, pre-condition failure");
// + class invariants.
do_f(p);
// Check post-conditions + class invariants.
}
private:
virtual void do_f(Parameters p) = 0;
};
...
class Concrete : public Contract1, public Contract2
{
private:
virtual void do_f(Parameters p); // From contract 1.
virtual void do_g(Parameters p); // From contract 2.
};
You can also use INT_MAX:
http://www.cplusplus.com/reference/climits/
it's equivalent to using numeric_limits.
You can make you request headers by yourself using:
// open a socket connection on port 80
$fp = fsockopen($host, 80);
// send the request headers:
fputs($fp, "POST $path HTTP/1.1\r\n");
fputs($fp, "Host: $host\r\n");
fputs($fp, "Referer: $referer\r\n");
fputs($fp, "Content-type: application/x-www-form-urlencoded\r\n");
fputs($fp, "Content-length: ". strlen($data) ."\r\n");
fputs($fp, "Connection: close\r\n\r\n");
fputs($fp, $data);
$result = '';
while(!feof($fp)) {
// receive the results of the request
$result .= fgets($fp, 128);
}
// close the socket connection:
fclose($fp);
Like writen on how make request
POCOs(Plain old CLR objects) are simply entities of your Domain. Normally when we use entity framework the entities are generated automatically for you. This is great but unfortunately these entities are interspersed with database access functionality which is clearly against the SOC (Separation of concern). POCOs are simple entities without any data access functionality but still gives the capabilities all EntityObject functionalities like
Here is a good start for this
You can also generate POCOs so easily from your existing Entity framework project using Code generators.
I'm very late to the party here, but if you use an IDE like PyCharm, there's an option in 'Edit Configurations' under the 'Run' menu (Run > Edit Configurations) where you can specify a default port. This of course is relevant only if you are debugging/testing through PyCharm.
I just tried the first answer from Brad Rem and came to this setting in the web.config under BasicHttpBinding:
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding bypassProxyOnLocal="False" useDefaultWebProxy="false" proxyAddress="http://127.0.0.1:8888" ...
...
</basicHttpBinding>
</bindings>
...
<system.serviceModel>
Hope this helps someone.
ok I figured out a crude way of doing it.
I store the "n" value in the for loop when condition is satisfied in a list (lets call it delList) then do the following:
for ii in sorted(delList, reverse=True):
tupleX.pop(ii)
Any other suggestions are welcome too.
Approaches 1 and 2 obviously don't work, because you get java.sql.Date
objects, per JPA/Hibernate spec, and not java.util.Date
. From approaches 3 and 4, I would rather choose the latter one, because it's more declarative, and will work with both field and getter annotations.
You have already laid out the solution 4 in your referenced blog post, as @tscho was kind to point out. Maybe defaultForType (see below) should give you the centralized solution you were looking for. Of course will will still need to differentiate between date (without time) and timestamp fields.
For future reference I will leave the summary of using your own Hibernate UserType here:
To make Hibernate give you java.util.Date
instances, you can use the @Type and @TypeDef annotations to define a different mapping of your java.util.Date java types to and from the database.
See the examples in the core reference manual here.
TimestampAsJavaUtilDateType
Add a @TypeDef annotation on one entity or in a package-info.java - both will be available globally for the session factory (see manual link above). You can use defaultForType to apply the type conversion on all mapped fields of type java.util.Date
.
@TypeDef
name = "timestampAsJavaUtilDate",
defaultForType = java.util.Date.class, /* applied globally */
typeClass = TimestampAsJavaUtilDateType.class
)
Optionally, instead of defaultForType
, you can annotate your fields/getters with @Type individually:
@Entity
public class MyEntity {
[...]
@Type(type="timestampAsJavaUtilDate")
private java.util.Date myDate;
[...]
}
P.S. To suggest a totally different approach: we usually just don't compare Date objects using equals() anyway. Instead we use a utility class with methods to compare e.g. only the calendar date of two Date instances (or another resolution such as seconds), regardless of the exact implementation type. That as worked well for us.
In a normal situation, variables are bound by scoping rule: Local variables work only within the defined function. Closure is a way of breaking this rule temporarily for convenience.
def n_times(a_thing)
return lambda{|n| a_thing * n}
end
in the above code, lambda(|n| a_thing * n}
is the closure because a_thing
is referred by the lambda (an anonymous function creator).
Now, if you put the resulting anonymous function in a function variable.
foo = n_times(4)
foo will break the normal scoping rule and start using 4 internally.
foo.call(3)
returns 12.
A query string is an array of parameters sent to a web page.
This url: http://page.asp?x=1&y=hello
Request.QueryString[0] is the same as
Request.QueryString["x"] and holds a string value "1"
Request.QueryString[1] is the same as
Request.QueryString["y"] and holds a string value "hello"
It looks like it is a bug open for this issue: Prettier Bug
None of above solution worked for me. The only thing that worked was, adding this line of code in package.json:
"prettier": {
"singleQuote": true
},
It's not doable with CSS2.1, but it is possible with CSS3 attribute substring-matching selectors (which are supported in IE7+):
div[class^="status-"], div[class*=" status-"]
Notice the space character in the second attribute selector. This picks up div
elements whose class
attribute meets either of these conditions:
[class^="status-"]
— starts with "status-"
[class*=" status-"]
— contains the substring "status-" occurring directly after a space character. Class names are separated by whitespace per the HTML spec, hence the significant space character. This checks any other classes after the first if multiple classes are specified, and adds a bonus of checking the first class in case the attribute value is space-padded (which can happen with some applications that output class
attributes dynamically).
Naturally, this also works in jQuery, as demonstrated here.
The reason you need to combine two attribute selectors as described above is because an attribute selector such as [class*="status-"]
will match the following element, which may be undesirable:
<div id='D' class='foo-class foo-status-bar bar-class'></div>
If you can ensure that such a scenario will never happen, then you are free to use such a selector for the sake of simplicity. However, the combination above is much more robust.
If you have control over the HTML source or the application generating the markup, it may be simpler to just make the status-
prefix its own status
class instead as Gumbo suggests.
A. Grab file data from the file field
The first thing to do is bind a function to the change event on your file field and a function for grabbing the file data:
// Variable to store your files
var files;
// Add events
$('input[type=file]').on('change', prepareUpload);
// Grab the files and set them to our variable
function prepareUpload(event)
{
files = event.target.files;
}
This saves the file data to a file variable for later use.
B. Handle the file upload on submit
When the form is submitted you need to handle the file upload in its own AJAX request. Add the following binding and function:
$('form').on('submit', uploadFiles);
// Catch the form submit and upload the files
function uploadFiles(event)
{
event.stopPropagation(); // Stop stuff happening
event.preventDefault(); // Totally stop stuff happening
// START A LOADING SPINNER HERE
// Create a formdata object and add the files
var data = new FormData();
$.each(files, function(key, value)
{
data.append(key, value);
});
$.ajax({
url: 'submit.php?files',
type: 'POST',
data: data,
cache: false,
dataType: 'json',
processData: false, // Don't process the files
contentType: false, // Set content type to false as jQuery will tell the server its a query string request
success: function(data, textStatus, jqXHR)
{
if(typeof data.error === 'undefined')
{
// Success so call function to process the form
submitForm(event, data);
}
else
{
// Handle errors here
console.log('ERRORS: ' + data.error);
}
},
error: function(jqXHR, textStatus, errorThrown)
{
// Handle errors here
console.log('ERRORS: ' + textStatus);
// STOP LOADING SPINNER
}
});
}
What this function does is create a new formData object and appends each file to it. It then passes that data as a request to the server. 2 attributes need to be set to false:
C. Upload the files
Quick and dirty php script to upload the files and pass back some info:
<?php // You need to add server side validation and better error handling here
$data = array();
if(isset($_GET['files']))
{
$error = false;
$files = array();
$uploaddir = './uploads/';
foreach($_FILES as $file)
{
if(move_uploaded_file($file['tmp_name'], $uploaddir .basename($file['name'])))
{
$files[] = $uploaddir .$file['name'];
}
else
{
$error = true;
}
}
$data = ($error) ? array('error' => 'There was an error uploading your files') : array('files' => $files);
}
else
{
$data = array('success' => 'Form was submitted', 'formData' => $_POST);
}
echo json_encode($data);
?>
IMP: Don't use this, write your own.
D. Handle the form submit
The success method of the upload function passes the data sent back from the server to the submit function. You can then pass that to the server as part of your post:
function submitForm(event, data)
{
// Create a jQuery object from the form
$form = $(event.target);
// Serialize the form data
var formData = $form.serialize();
// You should sterilise the file names
$.each(data.files, function(key, value)
{
formData = formData + '&filenames[]=' + value;
});
$.ajax({
url: 'submit.php',
type: 'POST',
data: formData,
cache: false,
dataType: 'json',
success: function(data, textStatus, jqXHR)
{
if(typeof data.error === 'undefined')
{
// Success so call function to process the form
console.log('SUCCESS: ' + data.success);
}
else
{
// Handle errors here
console.log('ERRORS: ' + data.error);
}
},
error: function(jqXHR, textStatus, errorThrown)
{
// Handle errors here
console.log('ERRORS: ' + textStatus);
},
complete: function()
{
// STOP LOADING SPINNER
}
});
}
Final note
This script is an example only, you'll need to handle both server and client side validation and some way to notify users that the file upload is happening. I made a project for it on Github if you want to see it working.
See docs.python.org:
When you’re done with a file, call f.close() to close it and free up any system resources taken up by the open file. After calling f.close(), attempts to use the file object will automatically fail.
Hence use close()
elegantly with try/finally
:
f = open('file.txt', 'r')
try:
# do stuff with f
finally:
f.close()
This ensures that even if # do stuff with f
raises an exception, f
will still be closed properly.
Note that open
should appear outside of the try
. If open
itself raises an exception, the file wasn't opened and does not need to be closed. Also, if open
raises an exception its result is not assigned to f
and it is an error to call f.close()
.
For the sake of completeness of this popular question, since version 1.0.0 of dplyr
, parameter .groups controls the grouping structure of the summarise
function after group_by
summarise help.
With .groups = "drop_last"
, summarise
drops the last level of grouping. This was the only result obtained before version 1.0.0.
library(dplyr)
library(scales)
original <- mtcars %>%
group_by (am, gear) %>%
summarise (n=n()) %>%
mutate(rel.freq = scales::percent(n/sum(n), accuracy = 0.1))
#> `summarise()` regrouping output by 'am' (override with `.groups` argument)
original
#> # A tibble: 4 x 4
#> # Groups: am [2]
#> am gear n rel.freq
#> <dbl> <dbl> <int> <chr>
#> 1 0 3 15 78.9%
#> 2 0 4 4 21.1%
#> 3 1 4 8 61.5%
#> 4 1 5 5 38.5%
new_drop_last <- mtcars %>%
group_by (am, gear) %>%
summarise (n=n(), .groups = "drop_last") %>%
mutate(rel.freq = scales::percent(n/sum(n), accuracy = 0.1))
dplyr::all_equal(original, new_drop_last)
#> [1] TRUE
With .groups = "drop"
, all levels of grouping are dropped. The result is turned into an independent tibble with no trace of the previous group_by
# .groups = "drop"
new_drop <- mtcars %>%
group_by (am, gear) %>%
summarise (n=n(), .groups = "drop") %>%
mutate(rel.freq = scales::percent(n/sum(n), accuracy = 0.1))
new_drop
#> # A tibble: 4 x 4
#> am gear n rel.freq
#> <dbl> <dbl> <int> <chr>
#> 1 0 3 15 46.9%
#> 2 0 4 4 12.5%
#> 3 1 4 8 25.0%
#> 4 1 5 5 15.6%
If .groups = "keep"
, same grouping structure as .data (mtcars, in this case). summarise
does not peel off any variable used in the group_by
.
Finally, with .groups = "rowwise"
, each row is it's own group. It is equivalent to "keep" in this situation
# .groups = "keep"
new_keep <- mtcars %>%
group_by (am, gear) %>%
summarise (n=n(), .groups = "keep") %>%
mutate(rel.freq = scales::percent(n/sum(n), accuracy = 0.1))
new_keep
#> # A tibble: 4 x 4
#> # Groups: am, gear [4]
#> am gear n rel.freq
#> <dbl> <dbl> <int> <chr>
#> 1 0 3 15 100.0%
#> 2 0 4 4 100.0%
#> 3 1 4 8 100.0%
#> 4 1 5 5 100.0%
# .groups = "rowwise"
new_rowwise <- mtcars %>%
group_by (am, gear) %>%
summarise (n=n(), .groups = "rowwise") %>%
mutate(rel.freq = scales::percent(n/sum(n), accuracy = 0.1))
dplyr::all_equal(new_keep, new_rowwise)
#> [1] TRUE
Another point that can be of interest is that sometimes, after applying group_by
and summarise
, a summary line can help.
# create a subtotal line to help readability
subtotal_am <- mtcars %>%
group_by (am) %>%
summarise (n=n()) %>%
mutate(gear = NA, rel.freq = 1)
#> `summarise()` ungrouping output (override with `.groups` argument)
mtcars %>% group_by (am, gear) %>%
summarise (n=n()) %>%
mutate(rel.freq = n/sum(n)) %>%
bind_rows(subtotal_am) %>%
arrange(am, gear) %>%
mutate(rel.freq = scales::percent(rel.freq, accuracy = 0.1))
#> `summarise()` regrouping output by 'am' (override with `.groups` argument)
#> # A tibble: 6 x 4
#> # Groups: am [2]
#> am gear n rel.freq
#> <dbl> <dbl> <int> <chr>
#> 1 0 3 15 78.9%
#> 2 0 4 4 21.1%
#> 3 0 NA 19 100.0%
#> 4 1 4 8 61.5%
#> 5 1 5 5 38.5%
#> 6 1 NA 13 100.0%
Created on 2020-11-09 by the reprex package (v0.3.0)
Hope you find this answer useful.
If indeed the goal is to see if a string contains the actual space character (as described in the title), as opposed to any other sort of whitespace characters, you can use:
string s = "Hello There";
bool fHasSpace = s.Contains(" ");
If you're looking for ways to detect whitespace, there's several great options below.
You can use Pillow.
pip install Pillow
image = base64.b64decode(str(base64String))
fileName = 'test.jpeg'
imagePath = FILE_UPLOAD_DIR + fileName
img = Image.open(io.BytesIO(image))
img.save(imagePath, 'jpeg')
return fileName
reference for complete source code: https://abhisheksharma.online/convert-base64-blob-to-image-file-in-python/
If you need to include non-ASCII alphabetic characters, and if your regex flavor supports Unicode, then
\A\pL+\z
would be the correct regex.
Some regex engines don't support this Unicode syntax but allow the \w
alphanumeric shorthand to also match non-ASCII characters. In that case, you can get all alphabetics by subtracting digits and underscores from \w
like this:
\A[^\W\d_]+\z
\A
matches at the start of the string, \z
at the end of the string (^
and $
also match at the start/end of lines in some languages like Ruby, or if certain regex options are set).
You can use
#pragma GCC push_options
#pragma GCC optimize ("O0")
your code
#pragma GCC pop_options
to disable optimizations since GCC 4.4.
See the GCC documentation if you need more details.
Probably you can go with this code to take actions as the checkbox is checked or unchecked.
$('#chk').on('click',function(){
if(this.checked==true){
alert('yes');
}else{
alert('no');
}
});
Shame on me...
I looked at the user guide and the first function is $this->db->insert_id();
This also works with activerecord inserts...
EDIT: I updated the link
You can do this with the hex codec. ie:
>>> s='000000000000484240FA063DE5D0B744ADBED63A81FAEA390000C8428640A43D5005BD44'
>>> s.decode('hex')
'\x00\x00\x00\x00\x00\x00HB@\xfa\x06=\xe5\xd0\xb7D\xad\xbe\xd6:\x81\xfa\xea9\x00\x00\xc8B\x86@\xa4=P\x05\xbdD'
I found a simple solution, Simply add your jars inside WEB-INF-->lib folder..
I use AQTime, it is one of the best profiling tools I've ever used. It isn't free but you can get a 30 day trial, so if you plan on a optimizing and profiling only one project and 30 days are enough for you then I would recommend using this application. (http://www.automatedqa.com/downloads/aqtime/index.asp)
goto cpanel and login as Main Admin or Super Administrator
find SSH/Shell Access ( you will find under the security tab of cpanel )
now give the username and password of Super Administrator as root
or whatyougave
note: do not give any username, cos, it needs permissions
once your into console type
type ' mysql
' and press enter now you find youself in
mysql>
/* and type here like */
mysql> set global net_buffer_length=1000000;
Query OK, 0 rows affected (0.00 sec)
mysql> set global max_allowed_packet=1000000000;
Query OK, 0 rows affected (0.00 sec)
Now upload and enjoy!!!
You can query the ALL_OBJECTS view:
select owner
, object_name
, object_type
from ALL_OBJECTS
where object_name = 'FOO'
To find synonyms:
select *
from ALL_SYNONYMS
where synonym_name = 'FOO'
Just to clarify, if a user user's SQL statement references an object name with no schema qualification (e.g. 'FOO'), Oracle FIRST checks the user's schema for an object of that name (including synonyms in that user's schema). If Oracle can't resolve the reference from the user's schema, Oracle then checks for a public synonym.
If you are looking specifically for constraints on a particular table_name:
select c.*
from all_constraints c
where c.table_name = 'FOO'
union all
select cs.*
from all_constraints cs
join all_synonyms s
on (s.table_name = cs.table_name
and s.table_owner = cs.owner
and s.synonym_name = 'FOO'
)
HTH
-- addendum:
If your user is granted access to the DBA_ views (e.g. if your user has been granted SELECT_CATALOG_ROLE), you can substitute 'DBA_
' in place of 'ALL_
' in the preceding SQL examples. The ALL_x
views only show objects which you have been granted privileges. The DBA_x
views will show all database objects, whether you have privileges on them or not.
The problem for me was not got the port from process.env.PORT
it is very important because Heroku and other services properly do a random port numbers to use.
So that is the code that work for me eventuly :
var app = require('express')();
var http = require('http').createServer(app);
const serverPort = process.env.PORT ; //<----- important
const io = require('socket.io')(http,{
cors: {
origin: '*',
methods: 'GET,PUT,POST,DELETE,OPTIONS'.split(','),
credentials: true
}
});
http.listen(serverPort,()=>{
console.log(`server listening on port ${serverPort}`)
})
Indeed, in the latest version of Spring Data, findOne returns an optional. If you want to retrieve the object from the Optional, you can simply use get() on the Optional. First of all though, a repository should return the optional to a service, which then handles the case in which the optional is empty. afterwards, the service should return the object to the controller.
From Get-ScriptDirectory to the Rescue blog entry ...
function Get-ScriptDirectory
{
$Invocation = (Get-Variable MyInvocation -Scope 1).Value
Split-Path $Invocation.MyCommand.Path
}
If you wish your class to be compatible with the Java Beans specification, so that tools utilizing reflection (e.g. JavaBuilders, JGoodies Binding) can recognize boolean getters, either use getXXXX()
or isXXXX()
as a method name. From the Java Beans spec:
8.3.2 Boolean properties
In addition, for boolean properties, we allow a getter method to match the pattern:
public boolean is
<PropertyName>()
;This “is<PropertyName>” method may be provided instead of a “get<PropertyName>” method, or it may be provided in addition to a “get<PropertyName>” method. In either case, if the “is<PropertyName>” method is present for a boolean property then we will use the “is<PropertyName>” method to read the property value. An example boolean property might be:
public boolean isMarsupial(); public void setMarsupial(boolean m);
first in your ajax call include success & error function and then check if it gives you error or what?
your code should be like this
$(document).ready(function (e) {
$('#imageUploadForm').on('submit',(function(e) {
e.preventDefault();
var formData = new FormData(this);
$.ajax({
type:'POST',
url: $(this).attr('action'),
data:formData,
cache:false,
contentType: false,
processData: false,
success:function(data){
console.log("success");
console.log(data);
},
error: function(data){
console.log("error");
console.log(data);
}
});
}));
$("#ImageBrowse").on("change", function() {
$("#imageUploadForm").submit();
});
});
The new urllib3 library has a nice documentation here
In order to get your desired result you shuld follow that:
Import urllib3
from bs4 import BeautifulSoup
url = 'http://www.thefamouspeople.com/singers.php'
http = urllib3.PoolManager()
response = http.request('GET', url)
soup = BeautifulSoup(response.data.decode('utf-8'))
The "decode utf-8" part is optional. It worked without it when i tried, but i posted the option anyway.
Source: User Guide
RFC 3066 gives the details of the allowed values (emphasis and links added):
All 2-letter subtags are interpreted as ISO 3166 alpha-2 country codes from [ISO 3166], or subsequently assigned by the ISO 3166 maintenance agency or governing standardization bodies, denoting the area to which this language variant relates.
I interpret that as meaning any valid (according to ISO 3166) 2-letter code is valid as a subtag. The RFC goes on to state:
Tags with second subtags of 3 to 8 letters may be registered with IANA, according to the rules in chapter 5 of this document.
By the way, that looks like a typo, since chapter 3 seems to relate to the the registration process, not chapter 5.
A quick search for the IANA registry reveals a very long list, of all the available language subtags. Here's one example from the list (which would be used as en-scouse
):
Type: variant
Subtag: scouse
Description: Scouse
Added: 2006-09-18
Prefix: en
Comments: English Liverpudlian dialect known as 'Scouse'
There are all sorts of subtags available; a quick scroll has already revealed fr-1694acad
(17th century French).
The usefulness of some of these (I would say the vast majority of these) tags, when it comes to documents designed for display in the browser, is limited. The W3C Internationalization specification simply states:
Browsers and other applications can use information about the language of content to deliver to users the most appropriate information, or to present information to users in the most appropriate way. The more content is tagged and tagged correctly, the more useful and pervasive such applications will become.
I'm struggling to find detailed information on how browsers behave when encountering different language tags, but they are most likely going to offer some benefit to those users who use a screen reader, which can use the tag to determine the language/dialect/accent in which to present the content.
Check if you have the correct file mentioned in form statement in HTML:
For eg:
form action="insert.php" method="POST">
</form>
when you are in trial.php but instead you give another fileName
The fix is really simple: just replace YOUR_API_KEY on the last line of your code with your actual API key!
If you don't have one, you can get it for free on the Google Developers Website.
This terminal command:
open /Applications/Python\ 3.7/Install\ Certificates.command
Found here: https://stackoverflow.com/a/57614113/6207266
Resolved it for me. With my config
pip install --upgrade certifi
had no impact.
The information is not available through document.cookie, but if you're really desperate for it, you could try performing a request through the XmlHttpRequest object to the current page and access the cookie header using getResponseHeader().
Another easy method in Netbeans is also avaiable here, There are libraries inside Netbeans itself,where the solutions for this type of situations are available.Select the relevant one as well.It is much easier.After doing the prescribed steps in the link,please restart Netbeans.
Step1:- Select Tools->Palette->Swing/AWT Components
Step2:- Click 'Add from JAR'in Palette Manager
Step3:- Browse to [NETBEANS HOME]\ide\modules\ext and select swingx-0.9.5.jar
Step4:- This will bring up a list of all the components available for the palette. Lots of goodies here! Select JXDatePicker.
Step5:- Select Swing Controls & click finish
Step6:- Restart NetBeans IDE and see the magic :)
Constructors don't return a type , just remove the return type which is void in your case. It would run fine then.
I have not seen many linq solutions here.
I am not sure of the performance implications, however I generally stick to linq
as rule of thumb and then optimize later if necessary.
public bool CompareTwoArrays(byte[] array1, byte[] array2)
{
return !array1.Where((t, i) => t != array2[i]).Any();
}
Please do note this only works if they are the same size arrays. an extension could look like so
public bool CompareTwoArrays(byte[] array1, byte[] array2)
{
if (array1.Length != array2.Length) return false;
return !array1.Where((t, i) => t != array2[i]).Any();
}
To elaborate on Breno's answer... For Windows 7 these steps worked for me:
;C:\Program Files\nodejs
C:\>
) type npm and hit enter; you should now see some help text (Usage: npm <command>
etc.) rather than "npm is not recognized..."Now you can start using npm!
I always use the time-stamp - so its not possible, that the file exists already:
import os
import shutil
import datetime
now = str(datetime.datetime.now())[:19]
now = now.replace(":","_")
src_dir="C:\\Users\\Asus\\Desktop\\Versand Verwaltung\\Versand.xlsx"
dst_dir="C:\\Users\\Asus\\Desktop\\Versand Verwaltung\\Versand_"+str(now)+".xlsx"
shutil.copy(src_dir,dst_dir)
A slightly updated answer (since I ran into this problem in different circumstances.)
When you connect to a server using SSL, the first thing the server does is present a certificate which says "I am api.dropbox.com." The certificate has a "subject" and the subject has a "CN" (short for "common name".) The certificate may also have one or more "subjectAltNames". When node.js connects to a server, node.js fetches this certificate, and then verifies that the domain name it thinks it's connecting to (api.dropbox.com) matches either the subject's CN or one of the altnames. Note that, in node 0.10.x, if you connect using an IP, the IP address has to be in the altnames - node.js will not try to verify the IP against the CN.
Setting the rejectUnauthorized
flag to false will get around this check, but first of all if the server is giving you different credentials than you are expecting, something fishy is going on, and second this will also bypass other checks - it's not a good idea if you're connecting over the Internet.
If you are using node >= 0.11.x, you can also specify a checkServerIdentity: function(host, cert)
function to the tls module, which should return undefined
if you want to allow the connection and throw an exception otherwise (although I don't know if request
will proxy this flag through to tls for you.) It can be handy to declare such a function and console.log(host, cert);
to figure out what the heck is going on.
Here's a more optimized version of Mike's answer above that gets the websites Content-Type properly, supports POST and GET request, and uses your browsers User-Agent so websites can identify your proxy as a browser. You can just simply set the URL by changing url =
and it will automatically set HTTP and HTTPS stuff without manually doing it.
var express = require('express')
var app = express()
var https = require('https');
var http = require('http');
const { response } = require('express');
app.use('/', function(clientRequest, clientResponse) {
var url;
url = 'https://www.google.com'
var parsedHost = url.split('/').splice(2).splice(0, 1).join('/')
var parsedPort;
var parsedSSL;
if (url.startsWith('https://')) {
parsedPort = 443
parsedSSL = https
} else if (url.startsWith('http://')) {
parsedPort = 80
parsedSSL = http
}
var options = {
hostname: parsedHost,
port: parsedPort,
path: clientRequest.url,
method: clientRequest.method,
headers: {
'User-Agent': clientRequest.headers['user-agent']
}
};
var serverRequest = parsedSSL.request(options, function(serverResponse) {
var body = '';
if (String(serverResponse.headers['content-type']).indexOf('text/html') !== -1) {
serverResponse.on('data', function(chunk) {
body += chunk;
});
serverResponse.on('end', function() {
// Make changes to HTML files when they're done being read.
body = body.replace(`example`, `Cat!` );
clientResponse.writeHead(serverResponse.statusCode, serverResponse.headers);
clientResponse.end(body);
});
}
else {
serverResponse.pipe(clientResponse, {
end: true
});
clientResponse.contentType(serverResponse.headers['content-type'])
}
});
serverRequest.end();
});
app.listen(3000)
console.log('Running on 0.0.0.0:3000')
You use List#get(int index)
to get an object with the index index
in the list. You use it like that:
List<ExampleClass> list = new ArrayList<ExampleClass>();
list.add(new ExampleClass());
list.add(new ExampleClass());
list.add(new ExampleClass());
ExampleClass exampleObj = list.get(2); // will get the 3rd element in the list (index 2);
There is GitHub Enterprise to satisfy your needs. And there is an open source "clone" of Github Enterprise.
PS: Now Github provides unlimited private repositories, bitbucket does the same. you can give a try to both. There are several other solutions as well.
As the documentation says, this method call returns "a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive)". This means that you will get numbers from 0 to 9 in your case. So you've done everything correctly by adding one to that number.
Generally speaking, if you need to generate numbers from min
to max
(including both), you write
random.nextInt(max - min + 1) + min
Check out the article Visual Studio .NET Platform Target Explained.
The default setting, "Any CPU", means that the assembly will run natively on the CPU it is currently running on. Meaning, it will run as 64-bit on a 64-bit machine and 32-bit on a 32-bit machine. If the assembly is called from a 64-bit application, it will perform as a 64-bit assembly and so on.
The above link has been reported to be broken, so here is another article with a similar explanation: What AnyCPU Really Means As Of .NET 4.5 and Visual Studio 11
Place the commandName
in .aspx page
<asp:Button ID="btnDelete" Text="Delete" runat="server" CssClass="CoolButtons" CommandName="DeleteData"/>
Subscribe the rowCommand
event for the grid and you can try like this,
protected void grdBillingdata_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "DeleteData")
{
GridViewRow row = (GridViewRow)(((Button)e.CommandSource).NamingContainer);
HiddenField hdnDataId = (HiddenField)row.FindControl("hdnDataId");
}
}
Without having a href
, the click will reload the current page, so you need something like this:
<a href="#" onclick="f1()">jhhghj</a>
Or prevent the scroll like this:
<a href="#" onclick="f1(); return false;">jhhghj</a>
Or return false
in your f1
function and:
<a href="#" onclick="return f1();">jhhghj</a>
....or, the unobtrusive way:
<a href="#" id="abc">jhg</a>
<a href="#" id="myLink">jhhghj</a>
<script type="text/javascript">
document.getElementById("myLink").onclick = function() {
document.getElementById("abc").href="xyz.php";
return false;
};
</script>
1) 51,983 is a string type number does not accept comma
so u should set it as text
<input type="text" name="commanumber" id="commanumber" value="1,99" step='0.01' min='0' />
replace , with .
and change type attribute to number
$(document).ready(function() {
var s = $('#commanumber').val().replace(/\,/g, '.');
$('#commanumber').attr('type','number');
$('#commanumber').val(s);
});
Check out http://jsfiddle.net/ydf3kxgu/
Hope this solves your Problem
I hope you won't mind a slight tangent, but thought you may be interested to know that besides F
(for float), D
(for double), and L
(for long), a proposal has been made to add suffixes for byte
and short
—Y
and S
respectively. This would eliminate to the need to cast to bytes when using literal syntax for byte (or short) arrays. Quoting the example from the proposal:
MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
cruddy code like
byte[] stuff = { 0x00, 0x7F, (byte)0x80, (byte)0xFF};
can be recoded as
byte[] ufum7 = { 0x00y, 0x7Fy, 0x80y, 0xFFy };
Joe Darcy is overseeing Project Coin for Java 7, and his blog has been an easy way to track these proposals.
I had the same issue. For me it helped to remove the .vs directory in the project folder.
If you prefer significant digits to fixed digits then, the signif command might be useful:
> signif(1.12345, digits = 3)
[1] 1.12
> signif(12.12345, digits = 3)
[1] 12.1
> signif(12345.12345, digits = 3)
[1] 12300
Have you tried this?
$('.myClass, .myOtherClass').removeClass('theclass');
The var
keyword in C#'s main benefit is to enhance readability, not functionality. Technically, the var
keywords allows for some other unlocks (e.g. use of anonymous objects), but that seems to be outside the scope of this question. Every variable declared with the var
keyword has a type. For instance, you'll find that the following code outputs "String".
var myString = "";
Console.Write(myString.GetType().Name);
Furthermore, the code above is equivalent to:
String myString = "";
Console.Write(myString.GetType().Name);
The var
keyword is simply C#'s way of saying "I can figure out the type for myString
from the context, so don't worry about specifying the type."
var myVariable = (MyType)null
or MyType myVariable = null
should work because you are giving the C# compiler context to figure out what type myVariable
should will be.
For more information:
Since you are on a mac, you could add yourself to the _www (the apache user group) group on your mac:
sudo dseditgroup -o edit -a $USER -t user _www
and add _www user to the wheel group which seems to be what the mac creates files as:
sudo dseditgroup -o edit -a _www -t user wheel
I think there are more solutions!
You can start the app, and here are 3 things you can do:
Settings
> Manage License...
> Remove License
, and that removes for all Jetbrains products*.File
> Close Project
, and follow the first step.Help
> Register...
> Remove license
.*In case you have a license for a pack of products. If not, you have to remove the license per product individually. Check the 3rd step.
if you omit the format
attribute from the attr
element, you can use it to reference a class from XML layouts.
Refactor > Rename
worksFind Usages
worksdon't specify a format
attribute in .../src/main/res/values/attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MyCustomView">
....
<attr name="give_me_a_class"/>
....
</declare-styleable>
</resources>
use it in some layout file .../src/main/res/layout/activity__main_menu.xml
<?xml version="1.0" encoding="utf-8"?>
<SomeLayout
xmlns:app="http://schemas.android.com/apk/res-auto">
<!-- make sure to use $ dollar signs for nested classes -->
<MyCustomView
app:give_me_a_class="class.type.name.Outer$Nested/>
<MyCustomView
app:give_me_a_class="class.type.name.AnotherClass/>
</SomeLayout>
parse the class in your view initialization code .../src/main/java/.../MyCustomView.kt
class MyCustomView(
context:Context,
attrs:AttributeSet)
:View(context,attrs)
{
// parse XML attributes
....
private val giveMeAClass:SomeCustomInterface
init
{
context.theme.obtainStyledAttributes(attrs,R.styleable.ColorPreference,0,0).apply()
{
try
{
// very important to use the class loader from the passed-in context
giveMeAClass = context::class.java.classLoader!!
.loadClass(getString(R.styleable.MyCustomView_give_me_a_class))
.newInstance() // instantiate using 0-args constructor
.let {it as SomeCustomInterface}
}
finally
{
recycle()
}
}
}
if you have two divs, you can use this to align the divs next to each other in the same row:
#keyword {_x000D_
float:left;_x000D_
margin-left:250px;_x000D_
position:absolute;_x000D_
}_x000D_
_x000D_
#bar {_x000D_
text-align:center;_x000D_
}
_x000D_
<div id="keyword">_x000D_
Keywords:_x000D_
</div>_x000D_
<div id="bar">_x000D_
<input type = textbox name ="keywords" value="" onSubmit="search()" maxlength=40>_x000D_
<input type = button name="go" Value="Go ahead and find" onClick="search()">_x000D_
</div>
_x000D_
Make sure you have Desktop Development with C++ installed. I was experiencing the same problem because I only had Universal Windows Platform Development installed.
You might need to uninstall antivirus (in my case I had to get rid of Avast).
This makes sure that crypto::cng
command will work. Otherwise it was giving me errors:
mimikatz $ crypto::cng
ERROR kull_m_patch_genericProcessOrServiceFromBuild ; OpenProcess (0x00000005)
After removing Avast:
mimikatz $ crypto::cng
"KeyIso" service patched
Magic. (:
Windows Defender is another program blocking the program to work, so you will need also to disable it for the time of using program at least.
One possible solution would to use regex.
'phone' => 'required|regex:/(01)[0-9]{9}/'
This will check the input starts with 01 and is followed by 9 numbers. By using regex you don't need the numeric
or size
validation rules.
If you want to reuse this validation method else where, it would be a good idea to create your own validation rule for validating phone numbers.
In your AppServiceProvider
's boot
method:
Validator::extend('phone_number', function($attribute, $value, $parameters)
{
return substr($value, 0, 2) == '01';
});
This will allow you to use the phone_number
validation rule anywhere in your application, so your form validation could be:
'phone' => 'required|numeric|phone_number|size:11'
In your validator extension you could also check if the $value
is numeric and 11 characters long.
string folderPath = "";
FolderBrowserDialog folderBrowserDialog1 = new FolderBrowserDialog();
if (folderBrowserDialog1.ShowDialog() == DialogResult.OK) {
folderPath = folderBrowserDialog1.SelectedPath ;
}
First I think you need to fix your lists, as the first node of a <ul>
must be a <li>
(stackoverflow ref). Once that is setup you can do this:
// note this array has outer scope
var phrases = [];
$('.phrase').each(function(){
// this is inner scope, in reference to the .phrase element
var phrase = '';
$(this).find('li').each(function(){
// cache jquery var
var current = $(this);
// check if our current li has children (sub elements)
// if it does, skip it
// ps, you can work with this by seeing if the first child
// is a UL with blank inside and odd your custom BLANK text
if(current.children().size() > 0) {return true;}
// add current text to our current phrase
phrase += current.text();
});
// now that our current phrase is completely build we add it to our outer array
phrases.push(phrase);
});
// note the comma in the alert shows separate phrases
alert(phrases);
Working jsfiddle.
One thing is if you get the .text()
of an upper level li
you will get all sub level text with it.
Keeping an array will allow for many multiple phrases to be extracted.
EDIT:
This should work better with an empty UL
with no LI
:
// outer scope
var phrases = [];
$('.phrase').each(function(){
// inner scope
var phrase = '';
$(this).find('li').each(function(){
// cache jquery object
var current = $(this);
// check for sub levels
if(current.children().size() > 0) {
// check is sublevel is just empty UL
var emptyULtest = current.children().eq(0);
if(emptyULtest.is('ul') && $.trim(emptyULtest.text())==""){
phrase += ' -BLANK- '; //custom blank text
return true;
} else {
// else it is an actual sublevel with li's
return true;
}
}
// if it gets to here it is actual li
phrase += current.text();
});
phrases.push(phrase);
});
// note the comma to separate multiple phrases
alert(phrases);
you must put object in your JSX, It`s easy way to do this just see my simple code here:
const link = [
{
name: "Cold Drink",
link: "/coldDrink"
},
{
name: "Hot Drink",
link: "/HotDrink"
},
{ name: "chease Cake", link: "/CheaseCake" } ]; and you must map this array in your code with simple object see this code :
const links = (this.props.link);
{links.map((item, i) => (
<li key={i}>
<Link to={item.link}>{item.name}</Link>
</li>
))}
I hope this answer will be helpful for you ...:)
I've found out that if your image is 72dpi it will give you the image size error. Use 96dpi instead. Hope this helps.
If you can't use "viewWillDisappear" or similar method, try to subclass UINavigationController. This is the header class:
#import <Foundation/Foundation.h>
@class MyViewController;
@interface CCNavigationController : UINavigationController
@property (nonatomic, strong) MyViewController *viewController;
@end
Implementation class:
#import "CCNavigationController.h"
#import "MyViewController.h"
@implementation CCNavigationController {
}
- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
@"This is the moment for you to do whatever you want"
[self.viewController doCustomMethod];
return [super popViewControllerAnimated:animated];
}
@end
In the other hand, you need to link this viewController to your custom NavigationController, so, in your viewDidLoad method for your regular viewController do this:
@implementation MyViewController {
- (void)viewDidLoad
{
[super viewDidLoad];
((CCNavigationController*)self.navigationController).viewController = self;
}
}
I tried this, it worked for me:
declare @b2 VARBINARY(MAX)
set @b2 = 0x54006800690073002000690073002000610020007400650073007400
SELECT CONVERT(nVARCHAR(1000), @b2, 0);
I 've been using ctrl + d
. It throws you out into the destination where You've started the sqlite3 command in the first place.
I spent around 6 hours on the same issue today. Inserts go at a 'regular' speed (less than 3sec per 100K) up until to 5MI (out of total 30MI) rows and then the performance sinks drastically (all the way down to 1min per 100K).
I will not list all of the things that did not work and cut straight to the meat.
I dropped a primary key on the target table (which was a GUID) and my 30MI or rows happily flowed to their destination at a constant speed of less than 3sec per 100K.
My simple fix to stop it putting speech marks around numeric values...
while($r = mysql_fetch_assoc($rs)){
while($elm=each($r))
{
if(is_numeric($r[$elm["key"]])){
$r[$elm["key"]]=intval($r[$elm["key"]]);
}
}
$rows[] = $r;
}
To insert a newline to output stream on Linux, I used:
sed -i "s/def/abc\\\ndef/" file1
Where file1
was:
def
Before the sed in-place replacement, and:
abc
def
After the sed in-place replacement. Please note the use of \\\n
. If the patterns have a "
inside it, escape using \"
.
Here author performed tests showed that integer unix timestamp is better than DateTime. Note, he used MySql. But I feel no matter what DB engine you use comparing integers are slightly faster than comparing dates so int index is better than DateTime index. Take T1 - time of comparing 2 dates, T2 - time of comparing 2 integers. Search on indexed field takes approximately O(log(rows)) time because index based on some balanced tree - it may be different for different DB engines but anyway Log(rows) is common estimation. (if you not use bitmask or r-tree based index). So difference is (T2-T1)*Log(rows) - may play role if you perform your query oftenly.
You can use this function in your application to add keys to indexed array.
public static function convertIndexedArrayToAssociative($indexedArr, $keys)
{
$resArr = array();
foreach ($indexedArr as $item)
{
$tmpArr = array();
foreach ($item as $key=>$value)
{
$tmpArr[$keys[$key]] = $value;
}
$resArr[] = $tmpArr;
}
return $resArr;
}
const styles = theme => ({_x000D_
contentClass:{_x000D_
overflow: 'hidden',_x000D_
textOverflow: 'ellipsis',_x000D_
display: '-webkit-box',_x000D_
WebkitLineClamp:1,_x000D_
WebkitBoxOrient:'vertical'_x000D_
} _x000D_
})
_x000D_
render () {_x000D_
return(_x000D_
<div className={classes.contentClass}>_x000D_
{'content'}_x000D_
</div>_x000D_
)_x000D_
}
_x000D_
You can use strip() or split() to control the spaces values as in the following:
words = " first second "
# Remove end spaces
def remove_end_spaces(string):
return "".join(string.rstrip())
# Remove the first and end spaces
def remove_first_end_spaces(string):
return "".join(string.rstrip().lstrip())
# Remove all spaces
def remove_all_spaces(string):
return "".join(string.split())
# Show results
print(words)
print(remove_end_spaces(words))
print(remove_first_end_spaces(words))
print(remove_all_spaces(words))
Iterating over the answer from Tao-Nhan Nguyen, accounting the original value set for every pod, adjusting it only if it's not greater than 8.0... Add the following to the Podfile:
post_install do |installer|
installer.pods_project.targets.each do |target|
target.build_configurations.each do |config|
if Gem::Version.new('8.0') > Gem::Version.new(config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'])
config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '8.0'
end
end
end
end
You would want to use CSS to achieve that.
say you have a table with the attribute id="my_table"
You would want to write the following in your css file
#my_table{
margin-top:10px //moves your table 10pixels down
margin-left:10px //moves your table 10pixels right
}
if you do not have a CSS file then you may just add margin-top:10px, margin-left:10px
to the style attribute in your table element like so
<table style="margin-top:10px; margin-left:10px;">
....
</table>
There are a lot of resources on the net describing CSS and HTML in detail
$("ul[data-group='Companies'] li[data-company='Microsoft']") //Get all elements with data-company="Microsoft" below "Companies"
$("ul[data-group='Companies'] li:not([data-company='Microsoft'])") //get all elements with data-company!="Microsoft" below "Companies"
Look in to jQuery Selectors :contains is a selector
here is info on the :contains selector
To get 'dataX = urllib.urlopen(url).read()' working in python3 (this would have been correct for python2) you must just change 2 little things.
1: The urllib statement itself (add the .request in the middle):
dataX = urllib.request.urlopen(url).read()
2: The import statement preceding it (change from 'import urlib' to:
import urllib.request
And it should work in python3 :)
Checkout Portfoliojs jQuery plugin: http://portfoliojs.com
This plugin supports Touch Devices, Desktops and Mobile Browsers. Also, It has pre-loading feature.
What you are doing is, you are accepting split response in two different variables, and strings.Split() is returning only one response and that is an array of string. you need to store it to single variable and then you can extract the part of string by fetching the index value of an array.
example :
var hostAndPort string
hostAndPort = "127.0.0.1:8080"
sArray := strings.Split(hostAndPort, ":")
fmt.Println("host : " + sArray[0])
fmt.Println("port : " + sArray[1])
app domain : localhost
site URL : http://localhost:4440/
worked for me with the new UI.
There seem to be a lot of confusion which was addressed only in comments by elclanrs and raina77ow, so let me post a clarifying answer.
From "string.splice
" one may expect that it, like the one for arrays:
The problem is, the 3d requirement can not be fulfilled because strings are immutable (related: 1, 2), I've found the most dedicated comment here:
In JavaScript strings are primitive value types and not objects (spec). In fact, as of ES5, they're one of the only 5 value types alongside
null
,undefined
,number
andboolean
. Strings are assigned by value and not by reference and are passed as such. Thus, strings are not just immutable, they are a value. Changing the string"hello"
to be"world"
is like deciding that from now on the number 3 is the number 4... it makes no sense.
So, with that in account, one may expect the "string.splice
" thing to only:
which is what substr
does; or, alternatively,
which is the subject of the next section.
If you care about optimizing, you should probably use the Mike's implementation:
String.prototype.splice = function(index, count, add) {
if (index < 0) {
index += this.length;
if (index < 0)
index = 0;
}
return this.slice(0, index) + (add || "") + this.slice(index + count);
}
Treating the out-of-boundaries index may vary, though. Depending on your needs, you may want:
if (index < 0) {
index += this.length;
if (index < 0)
index = 0;
}
if (index >= this.length) {
index -= this.length;
if (index >= this.length)
index = this.length - 1;
}
or even
index = index % this.length;
if (index < 0)
index = this.length + index;
If you don't care about performance, you may want to adapt Kumar's suggestion which is more straight-forward:
String.prototype.splice = function(index, count, add) {
var chars = this.split('');
chars.splice(index, count, add);
return chars.join('');
}
The difference in performances increases drastically with the length of the string. jsperf shows, that for strings with the length of 10 the latter solution (splitting & joining) is twice slower than the former solution (using slice), for 100-letter strings it's x5 and for 1000-letter strings it's x50, in Ops/sec it's:
10 letters 100 letters 1000 letters
slice implementation 1.25 M 2.00 M 1.91 M
split implementation 0.63 M 0.22 M 0.04 M
note that I've changed the 1st and 2d arguments when moving from 10 letters to 100 letters (still I'm surprised that the test for 100 letters runs faster than that for 10 letters).
None of the previous answers quite got to the bottom of my own confusion, so I'd like to add my own.
What I was missing is that lea
operations treat the use of parentheses different than how mov
does.
Think of C. Let's say I have an array of long
that I call array
. Now the expression array[i]
performs a dereference, loading the value from memory at the address array + i * sizeof(long)
[1].
On the other hand, consider the expression &array[i]
. This still contains the sub-expression array[i]
, but no dereferencing is performed! The meaning of array[i]
has changed. It no longer means to perform a deference but instead acts as a kind of a specification, telling &
what memory address we're looking for. If you like, you could alternatively think of the &
as "cancelling out" the dereference.
Because the two use-cases are similar in many ways, they share the syntax array[i]
, but the existence or absence of a &
changes how that syntax is interpreted. Without &
, it's a dereference and actually reads from the array. With &
, it's not. The value array + i * sizeof(long)
is still calculated, but it is not dereferenced.
The situation is very similar with mov
and lea
. With mov
, a dereference occurs that does not happen with lea
. This is despite the use of parentheses that occurs in both. For instance, movq (%r8), %r9
and leaq (%r8), %r9
. With mov
, these parentheses mean "dereference"; with lea
, they don't. This is similar to how array[i]
only means "dereference" when there is no &
.
An example is in order.
Consider the code
movq (%rdi, %rsi, 8), %rbp
This loads the value at the memory location %rdi + %rsi * 8
into the register %rbp
. That is: get the value in the register %rdi
and the value in the register %rsi
. Multiply the latter by 8, and then add it to the former. Find the value at this location and place it into the register %rbp
.
This code corresponds to the C line x = array[i];
, where array
becomes %rdi
and i
becomes %rsi
and x
becomes %rbp
. The 8
is the length of the data type contained in the array.
Now consider similar code that uses lea
:
leaq (%rdi, %rsi, 8), %rbp
Just as the use of movq
corresponded to dereferencing, the use of leaq
here corresponds to not dereferencing. This line of assembly corresponds to the C line x = &array[i];
. Recall that &
changes the meaning of array[i]
from dereferencing to simply specifying a location. Likewise, the use of leaq
changes the meaning of (%rdi, %rsi, 8)
from dereferencing to specifying a location.
The semantics of this line of code are as follows: get the value in the register %rdi
and the value in the register %rsi
. Multiply the latter by 8, and then add it to the former. Place this value into the register %rbp
. No load from memory is involved, just arithmetic operations [2].
Note that the only difference between my descriptions of leaq
and movq
is that movq
does a dereference, and leaq
doesn't. In fact, to write the leaq
description, I basically copy+pasted the description of movq
, and then removed "Find the value at this location".
To summarize: movq
vs. leaq
is tricky because they treat the use of parentheses, as in (%rsi)
and (%rdi, %rsi, 8)
, differently. In movq
(and all other instruction except lea
), these parentheses denote a genuine dereference, whereas in leaq
they do not and are purely convenient syntax.
[1] I've said that when array
is an array of long
, the expression array[i]
loads the value from the address array + i * sizeof(long)
. This is true, but there's a subtlety that should be addressed. If I write the C code
long x = array[5];
this is not the same as typing
long x = *(array + 5 * sizeof(long));
It seems that it should be based on my previous statements, but it's not.
What's going on is that C pointer addition has a trick to it. Say I have a pointer p
pointing to values of type T
. The expression p + i
does not mean "the position at p
plus i
bytes". Instead, the expression p + i
actually means "the position at p
plus i * sizeof(T)
bytes".
The convenience of this is that to get "the next value" we just have to write p + 1
instead of p + 1 * sizeof(T)
.
This means that the C code long x = array[5];
is actually equivalent to
long x = *(array + 5)
because C will automatically multiply the 5
by sizeof(long)
.
So in the context of this StackOverflow question, how is this all relevant? It means that when I say "the address array + i * sizeof(long)
", I do not mean for "array + i * sizeof(long)
" to be interpreted as a C expression. I am doing the multiplication by sizeof(long)
myself in order to make my answer more explicit, but understand that due to that, this expression should not be read as C. Just as normal math that uses C syntax.
[2] Side note: because all lea
does is arithmetic operations, its arguments don't actually have to refer to valid addresses. For this reason, it's often used to perform pure arithmetic on values that may not be intended to be dereferenced. For instance, cc
with -O2
optimization translates
long f(long x) {
return x * 5;
}
into the following (irrelevant lines removed):
f:
leaq (%rdi, %rdi, 4), %rax # set %rax to %rdi + %rdi * 4
ret
select to_timestamp(cast(epoch_ms/1000 as bigint))::date
worked for me
You can create your own method, passing throught the array and the value you want removed:
function removeItem(arr, item){
return arr.filter(f => f !== item)
}
Then you can call this with:
ary = removeItem(ary, 'seven');
You can't.
So just don't apply styles directly like that, and apply a class "foo", and then define that in your CSS specification:
a.foo { color : orange; }
a.foo:hover { font-weight : bold; }
insert into MyTable(field1, field2, id_backup)
select field1, field2, uniqueId from MyTable where uniqueId = @Id;
I had the same issue and the Microsoft.Office.Interop was not appearing in "Add Reference" option once I upgraded VS2012 to VS2015. I basically repaired the installation (Control Panel > Programs & Features > VS 2012 > Right click Change > Repair) and added the Microsoft Office component. After that the same solution started working.
In short, no, you can't.
Long answer, extension methods are just syntactic sugar. IE:
If you have an extension method on string let's say:
public static string SomeStringExtension(this string s)
{
//whatever..
}
When you then call it:
myString.SomeStringExtension();
The compiler just turns it into:
ExtensionClass.SomeStringExtension(myString);
So as you can see, there's no way to do that for static methods.
And another thing just dawned on me: what would really be the point of being able to add static methods on existing classes? You can just have your own helper class that does the same thing, so what's really the benefit in being able to do:
Bool.Parse(..)
vs.
Helper.ParseBool(..);
Doesn't really bring much to the table...
In general, it's not going to have enough of an impact to worry about, particularly since it's an intranet app and not a general-use Internet app. In particular, since it's intranet, SEO isn't a concern, since your intranet shouldn't be accessible to search engines. (and if it is, it isn't an intranet app).
And any framework worth it's salt either already has a default way to do this, or is fairly easy to change how it deals with multi-word URL components, so I wouldn't worry about it too much.
That said, here's how I see the various options:
Hyphen
Underscore
CamelCase
/
anyways. If you find that you have a URL component that is more than 2 "words" long, you should probably try to find a better name for that concept.From the GNU UPC website:
Compiler build fails with fatal error: gnu/stubs-32.h: No such file or directory
This error message shows up on the 64 bit systems where GCC/UPC multilib feature is enabled, and it indicates that 32 bit version of libc is not installed. There are two ways to correct this problem:
- Install 32 bit version of glibc (e.g. glibc-devel.i686 on Fedora, CentOS, ..)
- Disable 'multilib' build by supplying "--disable-multilib" switch on the compiler configuration command
If you have (or create) a single string, you can use np.fromstring:
import numpy as np
x = ["1.1", "2.2", "3.2"]
x = ','.join(x)
x = np.fromstring( x, dtype=np.float, sep=',' )
Note, x = ','.join(x)
transforms the x array to string '1.1, 2.2, 3.2'
. If you read a line from a txt file, each line will be already a string.
I have used Newtonsoft JSON.NET (Documentation) It allows you to create a class / object, populate the fields, and serialize as JSON.
public class ReturnData
{
public int totalCount { get; set; }
public List<ExceptionReport> reports { get; set; }
}
public class ExceptionReport
{
public int reportId { get; set; }
public string message { get; set; }
}
string json = JsonConvert.SerializeObject(myReturnData);
There are lots of explanation of Jmeter Summary, I have been using this tool from quite some time for generating performance testing report with relevant data. The explanation available on below link is right from the field experience:
Jmeter:Understanding Summary Report
This is one of the most useful report generated by Jmeter to undertstand the load test result.
# Label: Name of HTTP sample request send to server
# Samples : This Captures the total number of samples pushed to server. Suppose you put a Loop Controller to run it 5 times this particular request and then 2 iteration(Called Loop Count in Thread Group)is set and load test is run for 100 users, then the count that will be displayed here .... 1*5*2 * 100 =1000. Total = total number of samples send to server during entire run.
# Average : It's an average response time for a particular http request. This response time is in millisecond, and an average for 5 loops in two iteration for 100 users. Total = Average of total average of samples, means add all averages for all samples and divide by number of samples
# Min : Minmum time spend by sample requests send for this label. The total equals to the minimum time across all samples.
# Max : Maximum tie spend by sample requests send for this label The total equals to the maxmimum time across all samples.
# Std. Dev. : Knowing the standard deviation of your data set tells you how densely the data points are clustered around the mean. The smaller the standard deviation, the more consistent the data. Standard deviation should be less than or equal to half of the average time for a label. If it is more than that, then it means that something is wrong. you need to figure out the problem and fix it. https://en.wikipedia.org/wiki/Standard_deviation Total is euqals to highest deviation across all samples.
# Error: Total percentage of erros found for a particular sample request. 0.0% shows that all requests completed successfully. Total equals to percentage of errors samples in all samples (Total Samples)
# Throughput: Hits/sec, or total number of request per unit of time(sec, mins, hr) send to server during test.
endTime = lastSampleStartTime + lastSampleLoadTime startTime = firstSampleStartTime converstion = unit time conversion value Throughput = Numrequests / ((endTime - startTime)*conversion)
# KB/sec : Its mesuring throughput rate in Kilobytes per second.
# Avg. Bytes: Avegare of total bytes of data downloaded from server. Totals is average bytes across all samples.
So the thing with the sizeof operator is that it returns you the amount of storage needed, in bytes, to store the operand.
The amount of storage needed to store a char is always 1 byte. So the sizeof(char)
will always return 1.
char a[] = "aaaaa";
int len1 = sizeof(a)/sizeof(char); // length = 6
int len2 = sizeof(a); // length = 6;
This is the same for both len1
and len2
because this division of 1 does not influence the equation.
The reason why both len1
and len2
carry the value 6 has to do with the string termination char '\0'
. Which is also a char which adds another char to the length. Therefore your length is going to be 6 instead of the 5 you were expecting.
char *a = new char[10];
int length = sizeof(a)/sizeof(char);
You already mentioned that the length turns out to be 4 here, which is correct. Again, the sizeof operator returns the storage amount for the operand and in your case it is a pointer a
. A pointer requires 4 bytes of storage and therefore the length is 4 in this case. Since you probably compile it to a 32-bit binary. If you'd created a 64-bit binary the outcome would be 8.
This explanation might be here already be here. Just want to share my two cents.
This is my solution:
public static bool OverlappingPeriods(DateTime aStart, DateTime aEnd,
DateTime bStart, DateTime bEnd)
{
if (aStart > aEnd)
throw new ArgumentException("A start can not be after its end.");
if(bStart > bEnd)
throw new ArgumentException("B start can not be after its end.");
return !((aEnd < bStart && aStart < bStart) ||
(bEnd < aStart && bStart < aStart));
}
I unit tested it with 100% coverage.
This is an older question, but there is actually an answer to this in the PowerShell documentation. I had the same problem, and for once RTFM actually solved it. Almost.
Documentation for the -File parameter states that "In rare cases, you might need to provide a Boolean value for a switch parameter. To provide a Boolean value for a switch parameter in the value of the File parameter, enclose the parameter name and value in curly braces, such as the following: -File .\Get-Script.ps1 {-All:$False}"
I had to write it like this:
PowerShell.Exe -File MyFile.ps1 {-SomeBoolParameter:False}
So no '$' before the true/false statement, and that worked for me, on PowerShell 4.0
Well there are a few ways to go about this depending on the intended behavior, but this link should give you all the best solutions and not surprisingly is from Dianne Hackborn
http://groups.google.com/group/android-developers/browse_thread/thread/d2a5c203dad6ec42
Essentially you have the following options
FragmentManager.popBackStack(String name,
FragmentManager.POP_BACK_STACK_INCLUSIVE)
.FragmentManager.getBackStackEntryCount()
/getBackStackEntryAt().getId()
to retrieve the ID of the first entry on the back stack, and
FragmentManager.popBackStack(int id,
FragmentManager.POP_BACK_STACK_INCLUSIVE)
.FragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE)
is supposed to pop the entire back stack... I think the documentation for
that is just wrong. (Actually I guess it just doesn't cover the case where
you pass in POP_BACK_STACK_INCLUSIVE
), The border-spacing
property will work for this particular case.
table {
border-collapse:separate;
border-spacing: 0 1em;
}
Now, this seems to work:
$('#example').DataTable({
"info": false
});
it hides that div
, altogether
Yes, we can zip and unzip the file/folder using cmd. See the below command and simply you can copy past in cmd and change the directory and file name
To Zip/Compress File
powershell Compress-Archive D:\Build\FolderName D:\Build\FolderName.zip
To Unzip/Expand File
powershell expand-archive D:\Build\FileName.zip D:\deployments\FileName
break just breaks the loop & return gets control back to the caller method.
This should be working too using JPA 2.0 @MapsId annotation instead of Hibernate's GenericGenerator:
@Entity
public class Person {
@Id
@GeneratedValue
public int id;
@OneToOne
@PrimaryKeyJoinColumn
public OtherInfo otherInfo;
rest of attributes ...
}
@Entity
public class OtherInfo {
@Id
public int id;
@MapsId
@OneToOne
@JoinColumn(name="id")
public Person person;
rest of attributes ...
}
More details on this in Hibernate 4.1 documentation under section 5.1.2.2.7.
int number = 534;
String numberString = "" + number;
char firstLetterchar = numberString.charAt(0);
int firstDigit = Integer.parseInt("" + firstLetterChar);
Well if you know the basics behind them, it shouldn't be too hard.
Generally you create an array called "buckets" that contain the key and value, with an optional pointer to create a linked list.
When you access the hash table with a key, you process the key with a custom hash function which will return an integer. You then take the modulus of the result and that is the location of your array index or "bucket". Then you check the unhashed key with the stored key, and if it matches, then you found the right place.
Otherwise, you've had a "collision" and must crawl through the linked list and compare keys until you match. (note some implementations use a binary tree instead of linked list for collisions).
Check out this fast hash table implementation:
Here are a few ways to protect the images on your website.
1. Put a transparent layer or a low opaque mask over image
Usually source of the image is open to public on each webpage. So the real image is beneath this mask and become unreachable. Make sure that the mask image should be the same size as the original image.
<body>
<div style="background-image: url(real_background_image.jpg);">
<img src="transparent_image.gif" style="height:300px;width:250px" />
</div>
</body>
2. Break the image into small units using script
Super simple image tiles script is used to do this operation. The script will break the real image into pieces and hide the real image as watermarked. This is a very useful and effective method for protecting images but it will increase the request to server to load each image tiles.
Another option you could try is iptstate.
Use padding
on the cells and border-spacing
on the table. The former will give you cellpadding while the latter will give you cellspacing.
table { border-spacing: 5px; } /* cellspacing */
th, td { padding: 5px; } /* cellpadding */
As an alternative to the other (very good) answers, you could cast to uintptr_t
or intptr_t
(from stdint.h
/inttypes.h
) and use the corresponding integer conversion specifiers. This would allow more flexibility in how the pointer is formatted, but strictly speaking an implementation is not required to provide these typedefs.
reinterpret_cast
A cleaner way to do this:
class Book {
public Title: string;
public Price: number;
public Description: string;
constructor(public BookId: number, public Author: string){}
}
Then
var bks: Book[] = [
new Book(1, "vamsee")
];
Bitstamp has live bitcoin data that are publicly available in JSON
at this link. Do not try to access it more than 600 times in ten minutes or else they'll block your IP (plus, it's unnecessary anyway; read more here). The below is a C#
approach to getting live data:
using (var WebClient = new System.Net.WebClient())
{
var json = WebClient.DownloadString("https://www.bitstamp.net/api/ticker/");
string value = Convert.ToString(json);
// Parse/use from here
}
From here, you can parse the JSON
and store it in a database (or with MongoDB
insert it directly) and then access it.
For historic data (depending on the database - if that's how you approach it), do an insert from a flat file, which most databases allow you to use (for instance, with SQL Server
you can do a BULK INSERT
from a CSV
file).
you can run flutter clean
command
A form is not allowed to be a child element of a table
, tbody
or tr
. Attempting to put one there will tend to cause the browser to move the form to it appears after the table (while leaving its contents — table rows, table cells, inputs, etc — behind).
You can have an entire table inside a form. You can have a form inside a table cell. You cannot have part of a table inside a form.
Use one form around the entire table. Then either use the clicked submit button to determine which row to process (to be quick) or process every row (allowing bulk updates).
HTML 5 introduces the form
attribute. This allows you to provide one form per row outside the table and then associate all the form control in a given row with one of those forms using its id
.
You can use input type="reset"
<form action="/action_page.php">
text: <input type="text" name="email" /><br />
<input type="reset" defaultValue="Reset" />
</form>
If you need only an integer representing elapsed days since Jan. 1, 1970, you can try these:
// magic number=
// millisec * sec * min * hours
// 1000 * 60 * 60 * 24 = 86400000
public static final long MAGIC=86400000L;
public int DateToDays (Date date){
// convert a date to an integer and back again
long currentTime=date.getTime();
currentTime=currentTime/MAGIC;
return (int) currentTime;
}
public Date DaysToDate(int days) {
// convert integer back again to a date
long currentTime=(long) days*MAGIC;
return new Date(currentTime);
}
Shorter but less readable (slightly faster?):
public static final long MAGIC=86400000L;
public int DateToDays (Date date){
return (int) (date.getTime()/MAGIC);
}
public Date DaysToDate(int days) {
return new Date((long) days*MAGIC);
}
Hope this helps.
EDIT: This could work until Fri Jul 11 01:00:00 CET 5881580
I got this error when the text file I was trying to read contained a string that matched an antivirus signature on our firewall.
No, unlike in a lot of other languages, XSLT variables cannot change their values after they are created. You can however, avoid extraneous code with a technique like this:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes" omit-xml-declaration="yes"/>
<xsl:variable name="mapping">
<item key="1" v1="A" v2="B" />
<item key="2" v1="X" v2="Y" />
</xsl:variable>
<xsl:variable name="mappingNode"
select="document('')//xsl:variable[@name = 'mapping']" />
<xsl:template match="....">
<xsl:variable name="testVariable" select="'1'" />
<xsl:variable name="values" select="$mappingNode/item[@key = $testVariable]" />
<xsl:variable name="variable1" select="$values/@v1" />
<xsl:variable name="variable2" select="$values/@v2" />
</xsl:template>
</xsl:stylesheet>
In fact, once you've got the values
variable, you may not even need separate variable1
and variable2
variables. You could just use $values/@v1
and $values/@v2
instead.
i used bootstrap in a press site but it does not worked on IE8, i used css3-mediaqueries.js javascript but still not working. if you want your media query to work with this javascript file add screen to your media query line in css
here is an example :
<meta name="viewport" content="width=device-width" />
<style>
@media screen and (max-width:900px) {}
@media screen and (min-width:900px) and (max-width:1200px) {}
@media screen and (min-width:1200px) {}
</style>
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<script type="text/javascript" src="css3-mediaqueries.js"></script>
css Link line as simple as above line.
A complete example for someone who may want to use this to monitor a mount point on a server. This example will check if /var/spool is under 5G and email the person :
#!/bin/bash
# -----------------------------------------------------------------------------------------
# SUMMARY: Check if MOUNT is under certain quota, mail us if this is the case
# DETAILS: If under 5G we have it alert us via email. blah blah
# -----------------------------------------------------------------------------------------
# CRON: 0 0,4,8,12,16 * * * /var/www/httpd-config/server_scripts/clear_root_spool_log.bash
MOUNTP=/var/spool # mount drive to check
LIMITSIZE=5485760 # 5G = 10*1024*1024k # limit size in GB (FLOOR QUOTA)
FREE=$(df -k --output=avail "$MOUNTP" | tail -n1) # df -k not df -h
LOG=/tmp/log-$(basename ${0}).log
MAILCMD=mail
EMAILIDS="[email protected]"
MAILMESSAGE=/tmp/tmp-$(basename ${0})
# -----------------------------------------------------------------------------------------
function email_on_failure(){
sMess="$1"
echo "" >$MAILMESSAGE
echo "Hostname: $(hostname)" >>$MAILMESSAGE
echo "Date & Time: $(date)" >>$MAILMESSAGE
# Email letter formation here:
echo -e "\n[ $(date +%Y%m%d_%H%M%S%Z) ] Current Status:\n\n" >>$MAILMESSAGE
cat $sMess >>$MAILMESSAGE
echo "" >>$MAILMESSAGE
echo "*** This email generated by $(basename $0) shell script ***" >>$MAILMESSAGE
echo "*** Please don't reply this email, this is just notification email ***" >>$MAILMESSAGE
# sending email (need to have an email client set up or sendmail)
$MAILCMD -s "Urgent MAIL Alert For $(hostname) AWS Server" "$EMAILIDS" < $MAILMESSAGE
[[ -f $MAILMESSAGE ]] && rm -f $MAILMESSAGE
}
# -----------------------------------------------------------------------------------------
if [[ $FREE -lt $LIMITSIZE ]]; then
echo "Writing to $LOG"
echo "MAIL ERROR: Less than $((($FREE/1000))) MB free (QUOTA) on $MOUNTP!" | tee ${LOG}
echo -e "\nPotential Files To Delete:" | tee -a ${LOG}
find $MOUNTP -xdev -type f -size +500M -exec du -sh {} ';' | sort -rh | head -n20 | tee -a ${LOG}
email_on_failure ${LOG}
else
echo "Currently $(((($FREE-$LIMITSIZE)/1000))) MB of QUOTA available of on $MOUNTP. "
fi
conda create -n py27 python=2.7 ipykernel
source activate py27
pip install geocoder
According to my perspective, the main difference between script and program:
Scripts can be used with the other technologies. Example: PHP scripts, Javascripts, etc. can be used within HTML.
Programs are stand-alone chunks of code that can never be embedded into the other technologies.
If I am wrong at any place please correct me.I will admire your correction.
value
attribute (no CSS needed)Modern browsers will interpret the value
attribute and will display it as you expect. See MDN documentation.
<ol>_x000D_
<li value="3">This is item three.</li>_x000D_
<li value="50">This is item fifty.</li>_x000D_
<li value="100">This is item one hundred.</li>_x000D_
</ol>
_x000D_
Also have a look at the <ol>
article on MDN, especially the documentation for the start
and attribute.
Remove key and then add again the modified key, value pair as shown below :
JSONObject js = new JSONObject();
js.put("name", "rai");
js.remove("name");
js.put("name", "abc");
I haven't used your example; but conceptually its same.
It seems the docs/tool have been updated and you can now add the image
tag to your script. This was successful for me.
Example:
version: '2'
services:
baggins.api.rest:
image: my.image.name:rc2
build:
context: ../..
dockerfile: app/Docker/Dockerfile.release
ports:
...
Public Function connectDB() As OleDbConnection
Dim Con As New OleDbConnection
'Con.ConnectionString = "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;Initial Catalog=" & DBNAME & ";Data Source=" & DBSERVER & ";Pwd=" & DBPWD & ""
Con.ConnectionString = "Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DBNAME;Data Source=DBSERVER-TOSH;User ID=Sa;Pwd= & DBPWD"
Try
Con.Open()
Catch ex As Exception
showMessage(ex)
End Try
Return Con
End Function
XMLHttpRequest
is a standard object in the JavaScript Object model.
According to Wikipedia, XMLHttpRequest
first appeared in Internet Explorer 5 as an ActiveX object, but has since been made into a standard and has been included for use in JavaScript in the Mozilla family since 1.0, Apple Safari 1.2, Opera 7.60-p1, and IE 7.0.
The open()
method on the object takes the HTTP Method as an argument - and is specified as taking any valid HTTP method (see the item number 5 of the link) - including GET
, POST
, HEAD
, PUT
and DELETE
, as specified by RFC 2616.
check if you can hit your parent machine with:
ipconfig
(get your ip address)
ping <ip>
or telnet <ip> <port>
If you cannot get to the port, try adding a new inbound rule in your parent firewall allowing local ports.
I was then able to access http://<ip>:<port>
Assuming the column is set to support NULL as a value:
UPDATE YOUR_TABLE
SET column = NULL
Be aware of the database NULL handling - by default in SQL Server, NULL is an INT. So if the column is a different data type you need to CAST/CONVERT NULL to the proper data type:
UPDATE YOUR_TABLE
SET column = CAST(NULL AS DATETIME)
...assuming column
is a DATETIME data type in the example above.
Here's a suggestion: use two indices into the string, say start
and end
. start
points to the first character of the next string to extract, end
points to the character after the last one belonging to the next string to extract. start
starts at zero, end
gets the position of the first char after start
. Then you take the string between [start..end)
and add that to your array. You keep going until you hit the end of the string.
Is it very expensive to do this by json convert? But at least you have a 2 line solution and its generic. It does not matter eather if your datatable contains more or less fields than the object class:
Dim sSql = $"SELECT '{jobID}' AS ConfigNo, 'MainSettings' AS ParamName, VarNm AS ParamFieldName, 1 AS ParamSetId, Val1 AS ParamValue FROM StrSVar WHERE NmSp = '{sAppName} Params {jobID}'"
Dim dtParameters As DataTable = DBLib.GetDatabaseData(sSql)
Dim paramListObject As New List(Of ParameterListModel)()
If (Not dtParameters Is Nothing And dtParameters.Rows.Count > 0) Then
Dim json = Newtonsoft.Json.JsonConvert.SerializeObject(dtParameters).ToString()
paramListObject = Newtonsoft.Json.JsonConvert.DeserializeObject(Of List(Of ParameterListModel))(json)
End If
I had so many issues getting self-signed certificates working on macos/Chrome. Finally I found Mkcert, "A simple zero-config tool to make locally trusted development certificates with any names you'd like." https://github.com/FiloSottile/mkcert
Since static variables are shared by all instances of the class. For example if you are having following code
class Class<T> {
static void doIt(T object) {
// using T here
}
}
T is available only after an instance is created. But static methods can be used even before instances are available. So, Generic type parameters cannot be referenced inside static methods and variables
To end up with:
Array
object (not a NodeList
dressed up as an Array
)HTMLElements
, not Node
s force-casted to HTMLElement
sTry this:
let nodeList : NodeList = document.getElementsByTagName('script');
let elementList : Array<HTMLElement> = [];
if (nodeList) {
for (let i = 0; i < nodeList.length; i++) {
let node : Node = nodeList[i];
// Make sure it's really an Element
if (node.nodeType == Node.ELEMENT_NODE) {
elementList.push(node as HTMLElement);
}
}
}
Enjoy.
If your TextView
create click issues, than remove android:inputType=""
from your xml file.
Flexbox is the solution:
.separator {
display: flex;
align-items: center;
text-align: center;
}
.separator::before,
.separator::after {
content: '';
flex: 1;
border-bottom: 1px solid #000;
}
.separator:not(:empty)::before {
margin-right: .25em;
}
.separator:not(:empty)::after {
margin-left: .25em;
}
_x000D_
<div class="separator">Next section</div>
_x000D_
Nowadays every browser supports it, and you can ensure compatibility with decade-old browsers by adding respective vendor prefixes if needed. It would degrade gracefully anyways.
None: The file is not included in the project output group and is not compiled in the build process. An example is a text file that contains documentation, such as a Readme file.
Compile: The file is compiled into the build output. This setting is used for code files.
Content: Allows you to retrieve a file (in the same directory as the assembly) as a stream via Application.GetContentStream(URI). For this method to work, it needs a AssemblyAssociatedContentFile custom attribute which Visual Studio graciously adds when you mark a file as "Content"
Embedded resource: Embeds the file in an exclusive assembly manifest resource.
Resource (WPF only): Embeds the file in a shared (by all files in the assembly with similar setting) assembly manifest resource named AppName.g.resources.
Page (WPF only): Used to compile a xaml
file into baml
. The baml
is then embedded with the same technique as Resource
(i.e. available as `AppName.g.resources)
ApplicationDefinition (WPF only): Mark the XAML/class file that defines your application. You specify the code-behind with the x:Class="Namespace.ClassName" and set the startup form/page with StartupUri="Window1.xaml"
SplashScreen (WPF only): An image that is marked as SplashScreen
is shown automatically when an WPF application loads, and then fades
DesignData: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses mock types)
DesignDataWithDesignTimeCreatableTypes: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses actual types)
EntityDeploy: (Entity Framework): used to deploy the Entity Framework artifacts
CodeAnalysisDictionary: An XML file containing custom word dictionary for spelling rules
I just solved a similar problem by deleting all files in the website folder and then republished it.
Check it out this code, it works for me
// Slide up animation
<?xml version="1.0" encoding="utf-8"?> <set xmlns:android="http://schemas.android.com/apk/res/android" >
<translate
android:duration="@android:integer/config_mediumAnimTime"
android:fromYDelta="100%"
android:interpolator="@android:anim/accelerate_interpolator"
android:toXDelta="0" />
</set>
// Slide dowm animation
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" >
<translate
android:duration="@android:integer/config_mediumAnimTime"
android:fromYDelta="0%p"
android:interpolator="@android:anim/accelerate_interpolator"
android:toYDelta="100%p" />
</set>
// Style
<style name="DialogAnimation">
<item name="android:windowEnterAnimation">@anim/slide_up</item>
<item name="android:windowExitAnimation">@anim/slide_down</item>
</style>
// Inside Dialog Fragment
@Override
public void onActivityCreated(Bundle arg0) {
super.onActivityCreated(arg0);
getDialog().getWindow()
.getAttributes().windowAnimations = R.style.DialogAnimation;
}
Here is another way of doing the permutation of string with minimal code. We basically create a loop and then we keep swapping two characters at a time, Inside the loop we'll have the recursion. Notice,we only print when indexers reaches the length of our string. Example: ABC i for our starting point and our recursion param j for our loop
here is a visual help how it works from left to right top to bottom (is the order of permutation)
the code :
def permute(data, i, length):
if i==length:
print(''.join(data) )
else:
for j in range(i,length):
#swap
data[i], data[j] = data[j], data[i]
permute(data, i+1, length)
data[i], data[j] = data[j], data[i]
string = "ABC"
n = len(string)
data = list(string)
permute(data, 0, n)
As of rev 17 of the Android Developer Tools, the correct way to add a library jar when.using the tools and Eclipse is to create a directory called libs
on the same level as your src
and assets
directories and then drop the jar in there. Nothing else.required, the tools take care of all the rest for you automatically.
you can check by putting these code in php file.
<?php
if(in_array ('curl', get_loaded_extensions())) {
echo "CURL is available on your web server";
}
else{
echo "CURL is not available on your web server";
}
OR
var_dump(extension_loaded('curl'));
I had an embarrassing problem...
I got this error because I was rushing and forgot to put the app in INSTALLED_APPS
. You would think Django would raise a more descriptive error.
In case anyone looking for commonly supported formats by server
3g2|3gp|3gp2|3gpp|aac|aaf|aca|accdb|accde|accdt|acx|adt|adts|afm|ai|aif|aifc|aiff|appcache|application|art|asd|asf|asi|asm|asr|asx|atom|au|avi|axs|bas|bcpio|bin|bmp|c|cab|calx|cat|cdf|chm|class|clp|cmx|cnf|cod|cpio|cpp|crd|crl|crt|csh|css|csv|cur|dcr|deploy|der|dib|dir|disco|dll|dllconfig|dlm|doc|docm|docx|dot|dotm|dotx|dsp|dtd|dvi|dvr-ms|dwf|dwp|dxr|eml|emz|eot|eps|esd|etx|evy|exe|execonfig|fdf|fif|fla|flr|flv|gif|gtar|gz|h|hdf|hdml|hhc|hhk|hhp|hlp|hqx|hta|htc|htm|html|htt|hxt|ico|ics|ief|iii|inf|ins|isp|IVF|jar|java|jck|jcz|jfif|jpb|jpe|jpeg|jpg|js|json|jsonld|jsx|latex|less|lit|lpk|lsf|lsx|lzh|m13|m14|m1v|m2ts|m3u|m4a|m4v|man|manifest|map|mdb|mdp|me|mht|mhtml|mid|midi|mix|mmf|mno|mny|mov|movie|mp2|mp3|mp4|mp4v|mpa|mpe|mpeg|mpg|mpp|mpv2|ms|msi|mso|mvb|mvc|nc|nsc|nws|ocx|oda|odc|ods|oga|ogg|ogv|one|onea|onepkg|onetmp|onetoc|onetoc2|osdx|otf|p10|p12|p7b|p7c|p7m|p7r|p7s|pbm|pcx|pcz|pdf|pfb|pfm|pfx|pgm|pko|pma|pmc|pml|pmr|pmw|png|pnm|pnz|pot|potm|potx|ppam|ppm|pps|ppsm|ppsx|ppt|pptm|pptx|prf|prm|prx|ps|psd|psm|psp|pub|qt|qtl|qxd|ra|ram|rar|ras|rf|rgb|rm|rmi|roff|rpm|rtf|rtx|scd|sct|sea|setpay|setreg|sgml|sh|shar|sit|sldm|sldx|smd|smi|smx|smz|snd|snp|spc|spl|spx|src|ssm|sst|stl|sv4cpio|sv4crc|svg|svgz|swf|t|tar|tcl|tex|texi|texinfo|tgz|thmx|thn|tif|tiff|toc|tr|trm|ts|tsv|ttf|tts|txt|u32|uls|ustar|vbs|vcf|vcs|vdx|vml|vsd|vss|vst|vsto|vsw|vsx|vtx|wav|wax|wbmp|wcm|wdb|webm|wks|wm|wma|wmd|wmf|wml|wmlc|wmls|wmlsc|wmp|wmv|wmx|wmz|woff|woff2|wps|wri|wrl|wrz|wsdl|wtv|wvx|x|xaf|xaml|xap|xbap|xbm|xdr|xht|xhtml|xla|xlam|xlc|xlm|xls|xlsb|xlsm|xlsx|xlt|xltm|xltx|xlw|xml|xof|xpm|xps|xsd|xsf|xsl|xslt|xsn|xtp|xwd|z|zip
I really liked @brettdj's code, but then I found that when I added additional code to edit the copy, it overwrote my original sheet instead. I've tweaked his answer so that further code pointed at ws1
will affect the new sheet rather than the original.
Sub Test()
Dim ws1 as Worksheet
ThisWorkbook.Worksheets("Master").Copy
Set ws1 = ThisWorkbook.Worksheets("Master (2)")
End Sub
Consider a more pragmatic approach to the question of "doing it correctly".
console.log("about to bind scroll fx");
$(window).scroll(function() {
console.log("scroll bound, loop through div's");
$('div').each(function(){
If both of those log
s output correctly, then its likely the problem exists in your var declaration. To debug that, consider breaking it out into several lines:
var id='#'+$(this).attr('id');
console.log(id);
var off=$(id).offset().top;
var hei=$(id).height();
var winscroll=$(window).scrollTop();
var dif=hei+off-($(window).height());
By doing this, at least during debugging, you may find that the var id
is undefined, causing errors throughout the rest of the code. Is it possible some of your div
tags do not have id's?
It may be easier to use XPath to locate the nodes that you wish to delete. This stackoverflow thread might give you some ideas.
In your case you will find the four nodes that you want using this expression:
XmlDocument doc = new XmlDocument();
doc.Load(fileName);
XmlNodeList nodes = doc.SelectNodes("//Setting[@name='File1']");
Starting from Laravel 5.3 you can simply use :
if ($mentor->isNotEmpty()) {
//do something.
}
Documentation https://laravel.com/docs/5.5/collections#method-isnotempty
Whenever I attempt to remove the constraints that the system had to break, my constraints are no longer enough to satisfy the IB (ie "missing constraints" shows in the IB, which means they're incomplete and won't be used). I actually got around this by setting the constraint it wants to break to low priority, which (and this is an assumption) allows the system to break the constraint gracefully. It's probably not the best solution, but it solved my problem and the resulting constraints worked perfectly.
looks like you have maven project and so resources are in classpath by
go for
getClass().getResource("classpath:storedProcedures.sql")
I think it is considered "more pythonic" to just use in
when determining if a key already exists, as in
if start not in graph:
return None
When using Set-Content
instead of Out-File
, you can specify the encoding Byte
, which can be used to write a byte array to a file. This in combination with a custom UTF8 encoding which does not emit the BOM gives the desired result:
# This variable can be reused
$utf8 = New-Object System.Text.UTF8Encoding $false
$MyFile = Get-Content $MyPath -Raw
Set-Content -Value $utf8.GetBytes($MyFile) -Encoding Byte -Path $MyPath
The difference to using [IO.File]::WriteAllLines()
or similar is that it should work fine with any type of item and path, not only actual file paths.
Visual Studio also has a feature that will generate a Property from a private variable.
If you right-click on a variable, in the context menu that pops up, click on the "Refactor" item, and then choose Encapsulate Field.... This will create a getter/setter property for a variable.
I'm not too big a fan of this technique as it is a little bit awkward to use if you have to create a lot of getters/setters, and it puts the property directly below the private field, which bugs me, because I usually have all of my private fields grouped together, and this Visual Studio feature breaks my class' formatting.
it seems that the answers are unsatisfactory and I have since use my own code which is easier to understand
from datetime import datetime
from dateutil import relativedelta
date1 = datetime.strptime(str('2017-01-01'), '%Y-%m-%d')
date2 = datetime.strptime(str('2019-03-19'), '%Y-%m-%d')
difference = relativedelta.relativedelta(date2, date1)
months = difference.months
years = difference.years
# add in the number of months (12) for difference in years
months += 12 * difference.years
months
[Ljava.lang.Object;
is the name for Object[].class
, the java.lang.Class
representing the class of array of Object
.
The naming scheme is documented in Class.getName()
:
If this class object represents a reference type that is not an array type then the binary name of the class is returned, as specified by the Java Language Specification (§13.1).
If this class object represents a primitive type or
void
, then the name returned is the Java language keyword corresponding to the primitive type orvoid
.If this class object represents a class of arrays, then the internal form of the name consists of the name of the element type preceded by one or more
'['
characters representing the depth of the array nesting. The encoding of element type names is as follows:Element Type Encoding boolean Z byte B char C double D float F int I long J short S class or interface Lclassname;
Yours is the last on that list. Here are some examples:
// xxxxx varies
System.out.println(new int[0][0][7]); // [[[I@xxxxx
System.out.println(new String[4][2]); // [[Ljava.lang.String;@xxxxx
System.out.println(new boolean[256]); // [Z@xxxxx
The reason why the toString()
method on arrays returns String
in this format is because arrays do not @Override
the method inherited from Object
, which is specified as follows:
The
toString
method for classObject
returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:getClass().getName() + '@' + Integer.toHexString(hashCode())
Note: you can not rely on the toString()
of any arbitrary object to follow the above specification, since they can (and usually do) @Override
it to return something else. The more reliable way of inspecting the type of an arbitrary object is to invoke getClass()
on it (a final
method inherited from Object
) and then reflecting on the returned Class
object. Ideally, though, the API should've been designed such that reflection is not necessary (see Effective Java 2nd Edition, Item 53: Prefer interfaces to reflection).
toString
for arraysjava.util.Arrays
provides toString
overloads for primitive arrays and Object[]
. There is also deepToString
that you may want to use for nested arrays.
Here are some examples:
int[] nums = { 1, 2, 3 };
System.out.println(nums);
// [I@xxxxx
System.out.println(Arrays.toString(nums));
// [1, 2, 3]
int[][] table = {
{ 1, },
{ 2, 3, },
{ 4, 5, 6, },
};
System.out.println(Arrays.toString(table));
// [[I@xxxxx, [I@yyyyy, [I@zzzzz]
System.out.println(Arrays.deepToString(table));
// [[1], [2, 3], [4, 5, 6]]
There are also Arrays.equals
and Arrays.deepEquals
that perform array equality comparison by their elements, among many other array-related utility methods.
Use $dirty
flag to show the error only after user interacted with the input:
<div>
<input type="email" name="email" ng-model="user.email" required />
<span ng-show="form.email.$dirty && form.email.$error.required">Email is required</span>
</div>
If you want to trigger the errors only after the user has submitted the form than you may use a separate flag variable as in:
<form ng-submit="submit()" name="form" ng-controller="MyCtrl">
<div>
<input type="email" name="email" ng-model="user.email" required />
<span ng-show="(form.email.$dirty || submitted) && form.email.$error.required">
Email is required
</span>
</div>
<div>
<button type="submit">Submit</button>
</div>
</form>
function MyCtrl($scope){
$scope.submit = function(){
// Set the 'submitted' flag to true
$scope.submitted = true;
// Send the form to server
// $http.post ...
}
};
Then, if all that JS inside ng-show
expression looks too much for you, you can abstract it into a separate method:
function MyCtrl($scope){
$scope.submit = function(){
// Set the 'submitted' flag to true
$scope.submitted = true;
// Send the form to server
// $http.post ...
}
$scope.hasError = function(field, validation){
if(validation){
return ($scope.form[field].$dirty && $scope.form[field].$error[validation]) || ($scope.submitted && $scope.form[field].$error[validation]);
}
return ($scope.form[field].$dirty && $scope.form[field].$invalid) || ($scope.submitted && $scope.form[field].$invalid);
};
};
<form ng-submit="submit()" name="form">
<div>
<input type="email" name="email" ng-model="user.email" required />
<span ng-show="hasError('email', 'required')">required</span>
</div>
<div>
<button type="submit">Submit</button>
</div>
</form>
How about alias gcc99= gcc -std=c99
?
You might need to install the grunt-cli, try this before doing a npm install:
sudo npm install -g grunt-cli
That fixes the grunt does not exit for me, you'll also need a valid grunt file.
You can use the Regex.Split method, something like this:
Regex regex = new Regex(@"\bis\b");
string[] substrings = regex.Split("This is a sentence");
foreach (string match in substrings)
{
Console.WriteLine("'{0}'", match);
}
Edit: This satisfies the example you gave. Note that an ordinary String.Split will also split on the "is" at the end of the word "This", hence why I used the Regex method and included the word boundaries around the "is". Note, however, that if you just wrote this example in error, then String.Split will probably suffice.
You can do so by creating an array of dtype=object
. If you try to assign a long string to a normal numpy array, it truncates the string:
>>> a = numpy.array(['apples', 'foobar', 'cowboy'])
>>> a[2] = 'bananas'
>>> a
array(['apples', 'foobar', 'banana'],
dtype='|S6')
But when you use dtype=object
, you get an array of python object references. So you can have all the behaviors of python strings:
>>> a = numpy.array(['apples', 'foobar', 'cowboy'], dtype=object)
>>> a
array([apples, foobar, cowboy], dtype=object)
>>> a[2] = 'bananas'
>>> a
array([apples, foobar, bananas], dtype=object)
Indeed, because it's an array of objects, you can assign any kind of python object to the array:
>>> a[2] = {1:2, 3:4}
>>> a
array([apples, foobar, {1: 2, 3: 4}], dtype=object)
However, this undoes a lot of the benefits of using numpy, which is so fast because it works on large contiguous blocks of raw memory. Working with python objects adds a lot of overhead. A simple example:
>>> a = numpy.array(['abba' for _ in range(10000)])
>>> b = numpy.array(['abba' for _ in range(10000)], dtype=object)
>>> %timeit a.copy()
100000 loops, best of 3: 2.51 us per loop
>>> %timeit b.copy()
10000 loops, best of 3: 48.4 us per loop
Whatever approach you take, make sure in the end that you have an updated version of curl and libcurl. You can do curl --version
and see the versions.
Here's what I did to get the latest curl version installed in Ubuntu:
sudo add-apt-repository "deb http://mirrors.kernel.org/ubuntu wily main"
sudo apt-get update
sudo apt-get install curl
Try this snippet
list.onclick = function(e) {_x000D_
e.preventDefault();_x000D_
_x000D_
var elm = e.target;_x000D_
var audio = document.getElementById('audio');_x000D_
_x000D_
var source = document.getElementById('audioSource');_x000D_
source.src = elm.getAttribute('data-value');_x000D_
_x000D_
audio.load(); //call this to just preload the audio without playing_x000D_
audio.play(); //call this to play the song right away_x000D_
};
_x000D_
<ul style="list-style: none">_x000D_
<li>Audio Files_x000D_
<ul id="list">_x000D_
<li><a href="#" data-value="http://media.w3.org/2010/07/bunny/04-Death_Becomes_Fur.oga">Death_Becomes_Fur.oga</a></li>_x000D_
<li><a href="#" data-value="http://media.w3.org/2010/07/bunny/04-Death_Becomes_Fur.mp4">Death_Becomes_Fur.mp4</a></li>_x000D_
<li><a href="#" data-value="http://media.w3.org/2010/11/rrs006.oga">rrs006.oga</a></li>_x000D_
<li><a href="#" data-value="http://media.w3.org/2010/05/sound/sound_90.mp3">sound_90.mp3</a></li>_x000D_
</ul>_x000D_
</li>_x000D_
</ul>_x000D_
_x000D_
<audio id="audio" controls="controls">_x000D_
<source id="audioSource" src=""></source>_x000D_
Your browser does not support the audio format._x000D_
</audio>
_x000D_
JSFiddle http://jsfiddle.net/jm6ky/2/
After having used Waterboy's code over and over in multiple Python packages, I finally cast it into a tiny standalone Python package, which you can find here:
https://github.com/acschaefer/duallog
The code is well documented and easy to use. Simply download the .py
file and include it in your project, or install the whole package via pip install duallog
.