Android - Launcher Icon Size
I've posted a script for generating all platform icons for PhoneGap apps from a single SVG icon file. If you have existing bitmaps, I also include some notes that may help you to generate the SVG vectors from an existing bitmap. This won't work for all bitmaps but may for yours.
What does \0 stand for?
The null character '\0'
(also null terminator
), abbreviated NUL
, is a control character with the value zero
. Its the same in C and objective C
The character has much more significance in C and it serves as a reserved character used to signify the end of a string
,often called a null-terminated string
The length of a C string (an array containing the characters and terminated with a '\0'
character) is found by searching for the (first) NUL byte.
Dart SDK is not configured
Goto preferences -> Languages & Frameworks -> Flutter
Set your flutter sdk path
for example :-
/Users/apple/flutter-sdk/flutter
then apply your settings.
Make sure all dependencies are installed. if not
run - flutter pub get
to install dependencies
How to change navigation bar color in iOS 7 or 6?
The behavior of tintColor for bars has changed on iOS 7.0. It no longer affects the bar's background and behaves as described for the tintColor property added to UIView.
To tint the bar's background, please use -barTintColor.
navController.navigationBar.barTintColor = [UIColor navigationColor];
What are the differences and similarities between ffmpeg, libav, and avconv?
Confusing messages
These messages are rather misleading and understandably a source of confusion. Older Ubuntu versions used Libav which is a fork of the FFmpeg project. FFmpeg returned in Ubuntu 15.04 "Vivid Vervet".
The fork was basically a non-amicable result of conflicting personalities and development styles within the FFmpeg community. It is worth noting that the maintainer for Debian/Ubuntu switched from FFmpeg to Libav on his own accord due to being involved with the Libav fork.
The real ffmpeg
vs the fake one
For a while both Libav and FFmpeg separately developed their own version of ffmpeg
.
Libav then renamed their bizarro ffmpeg
to avconv
to distance themselves from the FFmpeg project. During the transition period the "not developed anymore" message was displayed to tell users to start using avconv
instead of their counterfeit version of ffmpeg
. This confused users into thinking that FFmpeg (the project) is dead, which is not true. A bad choice of words, but I can't imagine Libav not expecting such a response by general users.
This message was removed upstream when the fake "ffmpeg
" was finally removed from the Libav source, but, depending on your version, it can still show up in Ubuntu because the Libav source Ubuntu uses is from the ffmpeg-to-avconv transition period.
In June 2012, the message was re-worded for the package libav - 4:0.8.3-0ubuntu0.12.04.1
. Unfortunately the new "deprecated" message has caused additional user confusion.
Starting with Ubuntu 15.04 "Vivid Vervet", FFmpeg's ffmpeg
is back in the repositories again.
libav vs Libav
To further complicate matters, Libav chose a name that was historically used by FFmpeg to refer to its libraries (libavcodec, libavformat, etc). For example the libav-user mailing list, for questions and discussions about using the FFmpeg libraries, is unrelated to the Libav project.
How to tell the difference
If you are using avconv
then you are using Libav. If you are using ffmpeg
you could be using FFmpeg or Libav. Refer to the first line in the console output to tell the difference: the copyright notice will either mention FFmpeg or Libav.
Secondly, the version numbering schemes differ. Each of the FFmpeg or Libav libraries contains a version.h
header which shows a version number. FFmpeg will end in three digits, such as 57.67.100, and Libav will end in one digit such as 57.67.0. You can also view the library version numbers by running ffmpeg
or avconv
and viewing the console output.
If you want to use the real ffmpeg
Ubuntu 15.04 "Vivid Vervet" or newer
The real ffmpeg
is in the repository, so you can install it with:
apt-get install ffmpeg
For older Ubuntu versions
Your options are:
These methods are non-intrusive, reversible, and will not interfere with the system or any repository packages.
Another possible option is to upgrade to Ubuntu 15.04 "Vivid Vervet" or newer and just use ffmpeg
from the repository.
Also see
For an interesting blog article on the situation, as well as a discussion about the main technical differences between the projects, see The FFmpeg/Libav situation.
How do I create a random alpha-numeric string in C++?
#include <iostream>
#include <string>
#include <random>
std::string generateRandomId(size_t length = 0)
{
static const std::string allowed_chars {"123456789BCDFGHJKLMNPQRSTVWXZbcdfghjklmnpqrstvwxz"};
static thread_local std::default_random_engine randomEngine(std::random_device{}());
static thread_local std::uniform_int_distribution<int> randomDistribution(0, allowed_chars.size() - 1);
std::string id(length ? length : 32, '\0');
for (std::string::value_type& c : id) {
c = allowed_chars[randomDistribution(randomEngine)];
}
return id;
}
int main()
{
std::cout << generateRandomId() << std::endl;
}
How to navigate through a vector using iterators? (C++)
Vector's iterators are random access iterators which means they look and feel like plain pointers.
You can access the nth element by adding n to the iterator returned from the container's begin()
method, or you can use operator []
.
std::vector<int> vec(10);
std::vector<int>::iterator it = vec.begin();
int sixth = *(it + 5);
int third = *(2 + it);
int second = it[1];
Alternatively you can use the advance function which works with all kinds of iterators. (You'd have to consider whether you really want to perform "random access" with non-random-access iterators, since that might be an expensive thing to do.)
std::vector<int> vec(10);
std::vector<int>::iterator it = vec.begin();
std::advance(it, 5);
int sixth = *it;
How do I pass an object to HttpClient.PostAsync and serialize as a JSON body?
A simple solution is to use Microsoft ASP.NET Web API 2.2 Client
from NuGet.
Then you can simply do this and it'll serialize the object to JSON and set the Content-Type
header to application/json; charset=utf-8
:
var data = new
{
name = "Foo",
category = "article"
};
var client = new HttpClient();
client.BaseAddress = new Uri(baseUri);
client.DefaultRequestHeaders.Add("token", token);
var response = await client.PostAsJsonAsync("", data);
Field 'id' doesn't have a default value?
I was getting error while ExecuteNonQuery() resolved with adding AutoIncrement to Primary Key of my table. In your case if you don't want to add primary key then we must need to assign value to primary key.
ALTER TABLE `t1`
CHANGE COLUMN `id` `id` INT(11) NOT NULL AUTO_INCREMENT ;
Force HTML5 youtube video
If you're using the iframe embed api, you can put html5:1
as one of the playerVars
arguments, like so:
player = new YT.Player('player', {
height: '390',
width: '640',
videoId: '<VIDEO ID>',
playerVars: {
html5: 1
},
});
Totally works.
Android WebView Cookie Problem
I would save that session cookie as a preference and forcefully repopulate the cookie manager with it. It sounds that session cookie in not surviving Activity restart
How can I set Image source with base64
img = new Image();
img.src = "data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
img.outerHTML;
"<img src="data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==">"
JavaScript - Get Portion of URL Path
If you have an abstract URL string (not from the current window.location
), you can use this trick:
let yourUrlString = "http://example.com:3000/pathname/?search=test#hash";
let parser = document.createElement('a');
parser.href = yourUrlString;
parser.protocol; // => "http:"
parser.hostname; // => "example.com"
parser.port; // => "3000"
parser.pathname; // => "/pathname/"
parser.search; // => "?search=test"
parser.hash; // => "#hash"
parser.host; // => "example.com:3000"
Thanks to jlong
How to display errors on laravel 4?
Further to @cw24's answer • as of Laravel 5.4
you would instead have the following amendment in public/index.php
try {
$response = $kernel->handle(
$request = Illuminate\Http\Request::capture()
);
} catch(\Exception $e) {
echo "<pre>";
echo $e;
echo "</pre>";
}
And in my case, I had forgotten to fire up MySQL.
Which, by the way, is usually mysql.server start
in Terminal
A simple algorithm for polygon intersection
The way I worked about the same problem
- breaking the polygon into line segments
- find intersecting line using
IntervalTrees
or LineSweepAlgo
- finding a closed path using
GrahamScanAlgo
to find a closed path with adjacent vertices
- Cross Reference 3. with
DinicAlgo
to Dissolve them
note: my scenario was different given the polygons had a common vertice. But Hope this can help
How to access global js variable in AngularJS directive
I have tried these methods and find that they dont work for my needs. In my case, I needed to inject json rendered server side into the main template of the page, so when it loads and angular inits, the data is already there and doesnt have to be retrieved (large dataset).
The easiest solution that I have found is to do the following:
In your angular code outside of the app, module and controller definitions add in a global javascript value - this definition MUST come before the angular stuff is defined.
Example:
'use strict';
//my data variable that I need access to.
var data = null;
angular.module('sample', [])
Then in your controller:
.controller('SampleApp', function ($scope, $location) {
$scope.availableList = [];
$scope.init = function () {
$scope.availableList = data;
}
Finally, you have to init everything (order matters):
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.15/angular.min.js"></script>
<script src="/path/to/your/angular/js/sample.js"></script>
<script type="text/javascript">
data = <?= json_encode($cproducts); ?>
</script>
Finally initialize your controller and init function.
<div ng-app="samplerrelations" ng-controller="SamplerApp" ng-init="init();">
By doing this you will now have access to whatever data you stuffed into the global variable.
Unable to install Maven on Windows: "JAVA_HOME is set to an invalid directory"
My situation was a bit different.
JAVA_HOME
was set properly to point to 1.7
- Other Maven projects were working/building fine with 1.7 features.
PATH
was set properly.
- Everything was up-to-date.
Still my simple new Maven project was not working. What I noticed was the difference in the logs when I ran mvn clean install
. For my older Maven projects, it showed
[INFO] --- maven-compiler-plugin:2.3.2:compile (default-compile) @ oldProject---
But for my new project it showed:
[INFO] --- maven-compiler-plugin:2.0.2:compile (default-compile) @ newProject ---
So, I looked at the POM.xml
and noticed this thing in the old project's POM:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
Basically, this plugin tells which compiler version to use for compilation. Just added it to the new project's POM.xml
and things worked.
Hope it is useful to someone.
String to char array Java
A string to char array is as simple as
String str = "someString";
char[] charArray = str.toCharArray();
Can you explain a little more on what you are trying to do?
* Update *
if I am understanding your new comment, you can use a byte array and example is provided.
byte[] bytes = ByteBuffer.allocate(4).putInt(1695609641).array();
for (byte b : bytes) {
System.out.format("0x%x ", b);
}
With the following output
0x65 0x10 0xf3 0x29
ClientScript.RegisterClientScriptBlock?
Hai sridhar,
I found an answer for your prob
ClientScript.RegisterClientScriptBlock(GetType(), "sas", "<script> alert('Inserted successfully');</script>", true);
change false to true
or try this
ScriptManager.RegisterClientScriptBlock(ursavebuttonID, typeof(LinkButton or button), "sas", "<script> alert('Inserted successfully');</script>", true);
Spring default behavior for lazy-init
For those coming here and are using Java config you can set the Bean to lazy-init using annotations like this:
In the configuration class:
@Configuration
// @Lazy - For all Beans to load lazily
public class AppConf {
@Bean
@Lazy
public Demo demo() {
return new Demo();
}
}
For component scanning and auto-wiring:
@Component
@Lazy
public class Demo {
....
....
}
@Component
public class B {
@Autowired
@Lazy // If this is not here, Demo will still get eagerly instantiated to satisfy this request.
private Demo demo;
.......
}
Laravel view not found exception
Use this on your cmd then run your project.
php artisan config:cache php artisan route:cache php artisan
controller:cache php artisan optimize:clear
Access HTTP response as string in Go
bs := string(body)
should be enough to give you a string.
From there, you can use it as a regular string.
A bit as in this thread:
var client http.Client
resp, err := client.Get(url)
if err != nil {
log.Fatal(err)
}
defer resp.Body.Close()
if resp.StatusCode == http.StatusOK {
bodyBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
log.Fatal(err)
}
bodyString := string(bodyBytes)
log.Info(bodyString)
}
See also GoByExample.
As commented below (and in zzn's answer), this is a conversion (see spec).
See "How expensive is []byte(string)
?" (reverse problem, but the same conclusion apply) where zzzz mentioned:
Some conversions are the same as a cast, like uint(myIntvar)
, which just reinterprets the bits in place.
Sonia adds:
Making a string out of a byte slice, definitely involves allocating the string on the heap. The immutability property forces this.
Sometimes you can optimize by doing as much work as possible with []byte and then creating a string at the end. The bytes.Buffer
type is often useful.
C# Linq Group By on multiple columns
var consolidatedChildren =
from c in children
group c by new
{
c.School,
c.Friend,
c.FavoriteColor,
} into gcs
select new ConsolidatedChild()
{
School = gcs.Key.School,
Friend = gcs.Key.Friend,
FavoriteColor = gcs.Key.FavoriteColor,
Children = gcs.ToList(),
};
var consolidatedChildren =
children
.GroupBy(c => new
{
c.School,
c.Friend,
c.FavoriteColor,
})
.Select(gcs => new ConsolidatedChild()
{
School = gcs.Key.School,
Friend = gcs.Key.Friend,
FavoriteColor = gcs.Key.FavoriteColor,
Children = gcs.ToList(),
});
Auto-loading lib files in Rails 4
Use config.to_prepare to load you monkey patches/extensions for every request in development mode.
config.to_prepare do |action_dispatcher|
# More importantly, will run upon every request in development, but only once (during boot-up) in production and test.
Rails.logger.info "\n--- Loading extensions for #{self.class} "
Dir.glob("#{Rails.root}/lib/extensions/**/*.rb").sort.each do |entry|
Rails.logger.info "Loading extension(s): #{entry}"
require_dependency "#{entry}"
end
Rails.logger.info "--- Loaded extensions for #{self.class}\n"
end
Get line number while using grep
In order to display the results with the line numbers, you might try this
grep -nr "word to search for" /path/to/file/file
The result should be something like this:
linenumber: other data "word to search for" other data
How can I define an array of objects?
Some tslint
rules are disabling use of [], example message: Array type using 'T[]' is forbidden for non-simple types. Use 'Array<T>' instead.
Then you would write it like:
var userTestStatus: Array<{ id: number, name: string }> = Array(
{ "id": 0, "name": "Available" },
{ "id": 1, "name": "Ready" },
{ "id": 2, "name": "Started" }
);
How do I check the operating system in Python?
If you want to know on which platform you are on out of "Linux", "Windows", or "Darwin" (Mac), without more precision, you should use:
>>> import platform
>>> platform.system()
'Linux' # or 'Windows'/'Darwin'
The platform.system
function uses uname
internally.
How do I detect a click outside an element?
You can listen for a click event on document
and then make sure #menucontainer
is not an ancestor or the target of the clicked element by using .closest()
.
If it is not, then the clicked element is outside of the #menucontainer
and you can safely hide it.
$(document).click(function(event) {
var $target = $(event.target);
if(!$target.closest('#menucontainer').length &&
$('#menucontainer').is(":visible")) {
$('#menucontainer').hide();
}
});
Edit – 2017-06-23
You can also clean up after the event listener if you plan to dismiss the menu and want to stop listening for events. This function will clean up only the newly created listener, preserving any other click listeners on document
. With ES2015 syntax:
export function hideOnClickOutside(selector) {
const outsideClickListener = (event) => {
const $target = $(event.target);
if (!$target.closest(selector).length && $(selector).is(':visible')) {
$(selector).hide();
removeClickListener();
}
}
const removeClickListener = () => {
document.removeEventListener('click', outsideClickListener)
}
document.addEventListener('click', outsideClickListener)
}
Edit – 2018-03-11
For those who don't want to use jQuery. Here's the above code in plain vanillaJS (ECMAScript6).
function hideOnClickOutside(element) {
const outsideClickListener = event => {
if (!element.contains(event.target) && isVisible(element)) { // or use: event.target.closest(selector) === null
element.style.display = 'none'
removeClickListener()
}
}
const removeClickListener = () => {
document.removeEventListener('click', outsideClickListener)
}
document.addEventListener('click', outsideClickListener)
}
const isVisible = elem => !!elem && !!( elem.offsetWidth || elem.offsetHeight || elem.getClientRects().length ) // source (2018-03-11): https://github.com/jquery/jquery/blob/master/src/css/hiddenVisibleSelectors.js
NOTE:
This is based on Alex comment to just use !element.contains(event.target)
instead of the jQuery part.
But element.closest()
is now also available in all major browsers (the W3C version differs a bit from the jQuery one).
Polyfills can be found here: Element.closest()
Edit – 2020-05-21
In the case where you want the user to be able to click-and-drag inside the element, then release the mouse outside the element, without closing the element:
...
let lastMouseDownX = 0;
let lastMouseDownY = 0;
let lastMouseDownWasOutside = false;
const mouseDownListener = (event: MouseEvent) => {
lastMouseDownX = event.offsetX
lastMouseDownY = event.offsetY
lastMouseDownWasOutside = !$(event.target).closest(element).length
}
document.addEventListener('mousedown', mouseDownListener);
And in outsideClickListener
:
const outsideClickListener = event => {
const deltaX = event.offsetX - lastMouseDownX
const deltaY = event.offsetY - lastMouseDownY
const distSq = (deltaX * deltaX) + (deltaY * deltaY)
const isDrag = distSq > 3
const isDragException = isDrag && !lastMouseDownWasOutside
if (!element.contains(event.target) && isVisible(element) && !isDragException) { // or use: event.target.closest(selector) === null
element.style.display = 'none'
removeClickListener()
document.removeEventListener('mousedown', mouseDownListener); // Or add this line to removeClickListener()
}
}
CodeIgniter - File upload required validation
check this form validation extension library can help you to validate files, with current form validation when you validate upload field it treat as input filed where value is empty have look on this really good extension for form validation library
MY_Formvalidation
What does the "yield" keyword do?
There is another yield
use and meaning (since Python 3.3):
yield from <expr>
From PEP 380 -- Syntax for Delegating to a Subgenerator:
A syntax is proposed for a generator to delegate part of its operations to another generator. This allows a section of code containing 'yield' to be factored out and placed in another generator. Additionally, the subgenerator is allowed to return with a value, and the value is made available to the delegating generator.
The new syntax also opens up some opportunities for optimisation when one generator re-yields values produced by another.
Moreover this will introduce (since Python 3.5):
async def new_coroutine(data):
...
await blocking_action()
to avoid coroutines being confused with a regular generator (today yield
is used in both).
Error:Execution failed for task ':app:transformClassesWithDexForDebug'
I got this problem when I updated the Gradle plugin from version 1.2.3 to 1.5.0 as Android Studio suggested. In its web page, 1.5.0 appears to be a beta version.
Honestly, I don't know what advantages the version 1.5.0 has, but I'd rather wait until there's a stable version.
Of course, going back to 1.2.3 solved the issue.
issue ORA-00001: unique constraint violated coming in INSERT/UPDATE
This ORA error is occurred because of violation of unique constraint.
ORA-00001: unique constraint (constraint_name) violated
This is caused because of trying to execute an INSERT
or UPDATE
statement that has created a duplicate value in a field restricted by a unique index.
You can resolve this either by
- changing the constraint to allow duplicates, or
- drop the unique constraint or you can change your SQL to avoid duplicate inserts
disable Bootstrap's Collapse open/close animation
If you find the 1px jump before expanding and after collapsing when using the CSS solution a bit annoying, here's a simple JavaScript solution for Bootstrap 3...
Just add this somewhere in your code:
$(document).ready(
$('.collapse').on('show.bs.collapse hide.bs.collapse', function(e) {
e.preventDefault();
}),
$('[data-toggle="collapse"]').on('click', function(e) {
e.preventDefault();
$($(this).data('target')).toggleClass('in');
})
);
How to center HTML5 Videos?
All you have to do is set you video tag to display:block;
FTW the default is inline-block
FTL.
Try this
.center {
margin: 0 auto;
width: (whatever you want);
display: block;
}
unsigned APK can not be installed
You cannot install an unsigned application on a phone. You can only use it to test with an emulator. If you still want to go ahead, you can try self-signing the application.
Also, since you are installing the application from an SD card, I hope you have the necessary permissions set. Do go through stackoverflow.com and look at questions regarding installation of applications from an SD card - there have been many and they have been asked before.
Hope that helps.
Spring: How to inject a value to static field?
Spring uses dependency injection to populate the specific value when it finds the @Value annotation. However, instead of handing the value to the instance variable, it's handed to the implicit setter instead. This setter then handles the population of our NAME_STATIC value.
@RestController
//or if you want to declare some specific use of the properties file then use
//@Configuration
//@PropertySource({"classpath:application-${youeEnvironment}.properties"})
public class PropertyController {
@Value("${name}")//not necessary
private String name;//not necessary
private static String NAME_STATIC;
@Value("${name}")
public void setNameStatic(String name){
PropertyController.NAME_STATIC = name;
}
}
jQuery: get parent tr for selected radio button
Try this.
You don't need to prefix attribute name by @
in jQuery selector. Use closest()
method to get the closest parent element matching the selector.
$("#MwDataList input[name=selectRadioGroup]:checked").closest('tr');
You can simplify your method like this
function getSelectedRowGuid() {
return GetRowGuid(
$("#MwDataList > input:radio[@name=selectRadioGroup]:checked :parent tr"));
}
closest()
- Gets the first element that matches the selector, beginning at the current element and progressing up through the DOM tree.
As a side note, the ids of the elements should be unique on the page so try to avoid having same ids for radio buttons which I can see in your markup. If you are not going to use the ids then just remove it from the markup.
How to display an IFRAME inside a jQuery UI dialog
The problems were:
- iframe content comes from another domain
- iframe dimensions need to be adjusted for each video
The solution based on omerkirk's answer involves:
- Creating an iframe element
- Creating a dialog with
autoOpen: false, width: "auto", height: "auto"
- Specifying iframe source, width and height before opening the dialog
Here is a rough outline of code:
HTML
<div class="thumb">
<a href="http://jsfiddle.net/yBNVr/show/" data-title="Std 4:3 ratio video" data-width="512" data-height="384"><img src="http://dummyimage.com/120x90/000/f00&text=Std+4-3+ratio+video" /></a></li>
<a href="http://jsfiddle.net/yBNVr/1/show/" data-title="HD 16:9 ratio video" data-width="512" data-height="288"><img src="http://dummyimage.com/120x90/000/f00&text=HD+16-9+ratio+video" /></a></li>
</div>
jQuery
$(function () {
var iframe = $('<iframe frameborder="0" marginwidth="0" marginheight="0" allowfullscreen></iframe>');
var dialog = $("<div></div>").append(iframe).appendTo("body").dialog({
autoOpen: false,
modal: true,
resizable: false,
width: "auto",
height: "auto",
close: function () {
iframe.attr("src", "");
}
});
$(".thumb a").on("click", function (e) {
e.preventDefault();
var src = $(this).attr("href");
var title = $(this).attr("data-title");
var width = $(this).attr("data-width");
var height = $(this).attr("data-height");
iframe.attr({
width: +width,
height: +height,
src: src
});
dialog.dialog("option", "title", title).dialog("open");
});
});
Demo here and code here. And another example along similar lines
Sending event when AngularJS finished loading
Angular hasn't provided a way to signal when a page finished loading, maybe because "finished" depends on your application. For example, if you have hierarchical tree of partials, one loading the others. "Finish" would mean that all of them have been loaded. Any framework would have a hard time analyzing your code and understanding that everything is done, or still waited upon. For that, you would have to provide application-specific logic to check and determine that.
Is Laravel really this slow?
I faced 1.40s
while working with a pure laravel in development area!
the problem was using: php artisan serve
to run the webserver
when I used apache webserver (or NGINX) instead for the same code I got it down to 153ms
Change One Cell's Data in mysql
UPDATE TABLE <tablename>
SET <COLUMN=VALUE>
WHERE <CONDITION>
Example:
UPDATE TABLE teacher SET teacher_name='NSP' WHERE teacher_id='1'
Check if a Windows service exists and delete in PowerShell
More recent versions of PS have Remove-WmiObject. Beware of silent fails for $service.delete() ...
PS D:\> $s3=Get-WmiObject -Class Win32_Service -Filter "Name='TSATSvrSvc03'"
PS D:\> $s3.delete()
...
ReturnValue : 2
...
PS D:\> $?
True
PS D:\> $LASTEXITCODE
0
PS D:\> $result=$s3.delete()
PS D:\> $result.ReturnValue
2
PS D:\> Remove-WmiObject -InputObject $s3
Remove-WmiObject : Access denied
At line:1 char:1
+ Remove-WmiObject -InputObject $s3
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [Remove-WmiObject], ManagementException
+ FullyQualifiedErrorId : RemoveWMIManagementException,Microsoft.PowerShell.Commands.RemoveWmiObject
PS D:\>
For my situation I needed to be running 'As Administrator'
How to store and retrieve a dictionary with redis
Try rejson-py which is relatively new since 2017. Look at this introduction.
from rejson import Client, Path
rj = Client(host='localhost', port=6379)
# Set the key `obj` to some object
obj = {
'answer': 42,
'arr': [None, True, 3.14],
'truth': {
'coord': 'out there'
}
}
rj.jsonset('obj', Path.rootPath(), obj)
# Get something
print 'Is there anybody... {}?'.format(
rj.jsonget('obj', Path('.truth.coord'))
)
# Delete something (or perhaps nothing), append something and pop it
rj.jsondel('obj', Path('.arr[0]'))
rj.jsonarrappend('obj', Path('.arr'), 'something')
print '{} popped!'.format(rj.jsonarrpop('obj', Path('.arr')))
# Update something else
rj.jsonset('obj', Path('.answer'), 2.17)
How can I read a whole file into a string variable
This is how I did it:
package main
import (
"fmt"
"os"
"bytes"
"log"
)
func main() {
filerc, err := os.Open("filename")
if err != nil{
log.Fatal(err)
}
defer filerc.Close()
buf := new(bytes.Buffer)
buf.ReadFrom(filerc)
contents := buf.String()
fmt.Print(contents)
}
Algorithm to generate all possible permutations of a list?
Here's an implementation for ColdFusion (requires CF10 because of the merge argument to ArrayAppend() ):
public array function permutateArray(arr){
if (not isArray(arguments.arr) ) {
return ['The ARR argument passed to the permutateArray function is not of type array.'];
}
var len = arrayLen(arguments.arr);
var perms = [];
var rest = [];
var restPerms = [];
var rpLen = 0;
var next = [];
//for one or less item there is only one permutation
if (len <= 1) {
return arguments.arr;
}
for (var i=1; i <= len; i++) {
// copy the original array so as not to change it and then remove the picked (current) element
rest = arraySlice(arguments.arr, 1);
arrayDeleteAt(rest, i);
// recursively get the permutation of the rest of the elements
restPerms = permutateArray(rest);
rpLen = arrayLen(restPerms);
// Now concat each permutation to the current (picked) array, and append the concatenated array to the end result
for (var j=1; j <= rpLen; j++) {
// for each array returned, we need to make a fresh copy of the picked(current) element array so as to not change the original array
next = arraySlice(arguments.arr, i, 1);
arrayAppend(next, restPerms[j], true);
arrayAppend(perms, next);
}
}
return perms;
}
Based on KhanSharp's js solution above.
how to delete a specific row in codeigniter?
It will come in the url so you can get it by two ways.
Fist one
<td><?php echo anchor('textarea/delete_row', 'DELETE', 'id="$row->id"'); ?></td>
$id = $this->input->get('id');
2nd one.
$id = $this->uri->segment(3);
But in the second method you have to count the no. of segments in the url that on which no. your id come. 2,3,4 etc. then you have to pass. then in the ();
Programmatically Hide/Show Android Soft Keyboard
Did you try InputMethodManager.SHOW_IMPLICIT
in first window.
and for hiding in second window use InputMethodManager.HIDE_IMPLICIT_ONLY
EDIT :
If its still not working then probably you are putting it at the wrong place. Override onFinishInflate()
and show/hide there.
@override
public void onFinishInflate() {
/* code to show keyboard on startup */
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.showSoftInput(mUserNameEdit, InputMethodManager.SHOW_IMPLICIT);
}
Android: How to open a specific folder via Intent and show its content in a file browser?
Intent chooser = new Intent(Intent.ACTION_GET_CONTENT);
Uri uri = Uri.parse(Environment.getDownloadCacheDirectory().getPath().toString());
chooser.addCategory(Intent.CATEGORY_OPENABLE);
chooser.setDataAndType(uri, "*/*");
// startActivity(chooser);
try {
startActivityForResult(chooser, SELECT_FILE);
}
catch (android.content.ActivityNotFoundException ex)
{
Toast.makeText(this, "Please install a File Manager.",
Toast.LENGTH_SHORT).show();
}
In code above, if setDataAndType is "*/*" a builtin file browser is opened to pick any file, if I set "text/plain" Dropbox is opened. I have Dropbox, Google Drive installed. If I uninstall Dropbox only "*/*" works to open file browser. This is Android 4.4.2. I can download contents from Dropbox and for Google Drive, by getContentResolver().openInputStream(data.getData()).
#if DEBUG vs. Conditional("DEBUG")
I'm sure plenty will disagree with me, but having spent time as a build guy constantly hearing "But it works on my machine!", I take the standpoint that you should pretty much never use either. If you really need something for testing and debugging, figure out a way to make that testability seperate from the actual production code.
Abstract the scenarios with mocking in unit tests, make one off versions of things for one off scenarios you want to test, but don't put tests for debug into the code for binaries which you test and write for production release. These debug tests just hide possible bugs from devs so they aren't found until later in the process.
Add new row to excel Table (VBA)
Tbl.ListRows.Add
doesn't work for me and I believe lot others are facing the same problem. I use the following workaround:
'First check if the last row is empty; if not, add a row
If table.ListRows.count > 0 Then
Set lastRow = table.ListRows(table.ListRows.count).Range
For col = 1 To lastRow.Columns.count
If Trim(CStr(lastRow.Cells(1, col).Value)) <> "" Then
lastRow.Cells(1, col).EntireRow.Insert
'Cut last row and paste to second last
lastRow.Cut Destination:=table.ListRows(table.ListRows.count - 1).Range
Exit For
End If
Next col
End If
'Populate last row with the form data
Set lastRow = table.ListRows(table.ListRows.count).Range
Range("E7:E10").Copy
lastRow.PasteSpecial Transpose:=True
Range("E7").Select
Application.CutCopyMode = False
Hope it helps someone out there.
MySQL ON DUPLICATE KEY UPDATE for multiple rows insert in single query
I was looking for the same behavior using jdbi's BindBeanList and found the syntax is exactly the same as Peter Lang's answer above. In case anybody is running into this question, here's my code:
@SqlUpdate("INSERT INTO table_one (col_one, col_two) VALUES <beans> ON DUPLICATE KEY UPDATE col_one=VALUES(col_one), col_two=VALUES(col_two)")
void insertBeans(@BindBeanList(value = "beans", propertyNames = {"colOne", "colTwo"}) List<Beans> beans);
One key detail to note is that the propertyName you specify within @BindBeanList
annotation is not same as the column name you pass into the VALUES()
call on update.
How do I schedule a task to run at periodic intervals?
Advantage of ScheduledExecutorService
over Timer
I wish to offer you an alternative to Timer
using - ScheduledThreadPoolExecutor, an implementation of the ScheduledExecutorService interface. It has some advantages over the Timer class, according to "Java in Concurrency":
A Timer
creates only a single thread for executing timer tasks. If a
timer task takes too long to run, the timing accuracy of other
TimerTask
can suffer. If a recurring TimerTask
is scheduled to run
every 10 ms and another Timer-Task takes 40 ms to run, the recurring
task either (depending on whether it was scheduled at fixed rate or
fixed delay) gets called four times in rapid succession after the
long-running task completes, or "misses" four invocations completely.
Scheduled thread pools address this limitation by letting you provide
multiple threads for executing deferred and periodic tasks.
Another problem with Timer is that it behaves poorly if a TimerTask
throws an unchecked exception. Also, called "thread leakage"
The Timer thread doesn't catch the exception, so an unchecked
exception thrown from a TimerTask
terminates the timer thread. Timer
also doesn't resurrect the thread in this situation; instead, it
erroneously assumes the entire Timer was cancelled. In this case,
TimerTasks that are already scheduled but not yet executed are never
run, and new tasks cannot be scheduled.
And another recommendation if you need to build your own scheduling service, you may still be able to take advantage of the library by using a DelayQueue
, a BlockingQueue
implementation that provides the scheduling functionality of ScheduledThreadPoolExecutor
. A DelayQueue
manages a collection of Delayed objects. A Delayed has a delay time associated with it: DelayQueue
lets you take an element only if its delay has expired. Objects are returned from a DelayQueue
ordered by the time associated with their delay.
SSIS Convert Between Unicode and Non-Unicode Error
On the above example I kept losing the values, I think that delaying the Validation will allow the new data types to be saved as part of the meta data.
On the connection Manager for 'Excel Connection Manager' set the Delay Validation to False from the Properties.
Then on the data flow Destination task for Excel set the ValidationExternalMetaData to False, again from the properties.
This will now allow you to right click on the Excel Destination Task and go to Advanced Editor for Excel Destination --> far right tab - Input and Output Properties. In the External Columns folder section you will be able to now change the Data Types and Length values of the problematic columns and this can now be saved.
Good Luck!
Undo git stash pop that results in merge conflict
As it turns out, Git is smart enough not to drop a stash if it doesn't apply cleanly. I was able to get to the desired state with the following steps:
- To unstage the merge conflicts:
git reset HEAD .
(note the trailing dot)
- To save the conflicted merge (just in case):
git stash
- To return to master:
git checkout master
- To pull latest changes:
git fetch upstream; git merge upstream/master
- To correct my new branch:
git checkout new-branch; git rebase master
- To apply the correct stashed changes (now 2nd on the stack):
git stash apply stash@{1}
sendmail: how to configure sendmail on ubuntu?
Combine two answers above, I finally make it work. Just be careful that the first single quote for each string is a backtick (`) in file sendmail.mc.
#Change to your mail config directory:
cd /etc/mail
#Make a auth subdirectory
mkdir auth
chmod 700 auth #maybe not, because I cannot apply cmd "cd auth" if I do so.
#Create a file with your auth information to the smtp server
cd auth
touch client-info
#In the file, put the following, matching up to your smtp server:
AuthInfo:your.isp.net "U:root" "I:user" "P:password"
#Generate the Authentication database, make both files readable only by root
makemap hash client-info < client-info
chmod 600 client-info
cd ..
#Add the following lines to sendmail.mc. Make sure you update your smtp server
#The first single quote for each string should be changed to a backtick (`) like this:
define(`SMART_HOST',`your.isp.net')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE(`authinfo',`hash /etc/mail/auth/client-info')dnl
#run
sudo sendmailconfig
Sleeping in a batch file
UPDATE
The timeout
command, available from Windows Vista and onwards should be the command used, as described in another answer to this question. What follows here is an old answer.
Old answer
If you have Python installed, or don't mind installing it (it has other uses too :), just create the following sleep.py script and add it somewhere in your PATH:
import time, sys
time.sleep(float(sys.argv[1]))
It will allow sub-second pauses (for example, 1.5 sec, 0.1, etc.), should you have such a need. If you want to call it as sleep
rather than sleep.py
, then you can add the .PY
extension to your PATHEXT environment variable. On Windows XP, you can edit it in:
My Computer ? Properties (menu) ? Advanced (tab) ? Environment Variables (button) ? System variables (frame)
append new row to old csv file python
# I like using the codecs opening in a with
field_names = ['latitude', 'longitude', 'date', 'user', 'text']
with codecs.open(filename,"ab", encoding='utf-8') as logfile:
logger = csv.DictWriter(logfile, fieldnames=field_names)
logger.writeheader()
# some more code stuff
for video in aList:
video_result = {}
video_result['date'] = video['snippet']['publishedAt']
video_result['user'] = video['id']
video_result['text'] = video['snippet']['description'].encode('utf8')
logger.writerow(video_result)
Excel SUMIF between dates
this works, and can be adapted for weeks or anyother frequency i.e. weekly, quarterly etc...
=SUMIFS(B12:B11652,A12:A11652,">="&DATE(YEAR(C12),MONTH(C12),1),A12:A11652,"<"&DATE(YEAR(C12),MONTH(C12)+1,1))
Removing duplicate rows in Notepad++
Search for the regular expression: \b(\w+)\b([\w\W]*)\b\1\b
Replace it with: $1$2
Hit the Replace button until there are no more matches for the regular expression in your file.
Firefox 'Cross-Origin Request Blocked' despite headers
I faced similar problem, and I think is valid to be registered how I fixed it:
I have a system built basically over Symfony 3. For self learn and performance purposes I decided to write few scripts using GoLang, also, an API with public access.
My Go API expects Json format params, and also return Json format response
To call those GoApi's I am using, most, $.ajax ( jQuery )
The first test was a deception: the (un)famous "Cross-Origin Request Blocked" pop up !
Then, I tried to set the "Access-Control-Allow-Origin: *" On apache conf, htaccess, php, javascript and anywhere I could find on google !
But, even, same frustrating error !!!
The Solution was simple :
I had to make "POST" requests instead "GET" .
To achieve that I had to adjust both, GoLang and JavaScript to use GET !
Once it done, no more Cross-Origin Request Blocked for me !!!
Hope it Helps
PS:
I am using apache and Vhost, on Directory Block I have
Header always set Access-Control-Allow-Origin "*"
Header always set Access-Control-Allow-Methods "POST, GET, OPTIONS, DELETE, PUT"
Remember : "*" means that you will accept requests from anyone !!! (Which may be a security lack )
In my case it is ok, because it will be an public API
PS2:
My Headers
Response headers
Access-Control-Allow-Credentials true
Access-Control-Allow-Headers Authorization
Access-Control-Allow-Methods GET, POST, PUT
Access-Control-Allow-Origin http://localhost
Content-Length 164
Content-Type application/json; charset=UTF-8
Date Tue, 07 May 2019 20:33:52 GMT
Request headers (469 B)
Accept application/json, text/javascript, */*; q=0.01
Accept-Encoding gzip, deflate
Accept-Language en-US,en;q=0.5
Connection keep-alive
Content-Length 81
Content-Type application/x-www-form-urlencoded; charset=UTF-8
Host localhost:9003
Origin http://localhost
Referer http://localhost/fibootkt/MY_app_dev.php/MyTest/GoAPI
User-Agent Mozilla/5.0 (Macintosh; Intel …) Gecko/20100101 Firefox/66.0
How do you take a git diff file, and apply it to a local branch that is a copy of the same repository?
It seems like you can also use the patch command. Put the diff in the root of the repository and run patch
from the command line.
patch -i yourcoworkers.diff
or
patch -p0 -i yourcoworkers.diff
You may need to remove the leading folder structure if they created the diff without using --no-prefix
.
If so, then you can remove the parts of the folder that don't apply using:
patch -p1 -i yourcoworkers.diff
The -p(n) signifies how many parts of the folder structure to remove.
More information on creating and applying patches here.
You can also use
git apply yourcoworkers.diff --stat
to see if the diff by default will apply any changes. It may say 0 files affected if the patch is not applied correctly (different folder structure).
How to secure an ASP.NET Web API
Web API introduced an Attribute [Authorize]
to provide security. This can be set globally (global.asx)
public static void Register(HttpConfiguration config)
{
config.Filters.Add(new AuthorizeAttribute());
}
Or per controller:
[Authorize]
public class ValuesController : ApiController{
...
Of course your type of authentication may vary and you may want to perform your own authentication, when this occurs you may find useful inheriting from Authorizate Attribute and extending it to meet your requirements:
public class DemoAuthorizeAttribute : AuthorizeAttribute
{
public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext)
{
if (Authorize(actionContext))
{
return;
}
HandleUnauthorizedRequest(actionContext);
}
protected override void HandleUnauthorizedRequest(System.Web.Http.Controllers.HttpActionContext actionContext)
{
var challengeMessage = new System.Net.Http.HttpResponseMessage(System.Net.HttpStatusCode.Unauthorized);
challengeMessage.Headers.Add("WWW-Authenticate", "Basic");
throw new HttpResponseException(challengeMessage);
}
private bool Authorize(System.Web.Http.Controllers.HttpActionContext actionContext)
{
try
{
var someCode = (from h in actionContext.Request.Headers where h.Key == "demo" select h.Value.First()).FirstOrDefault();
return someCode == "myCode";
}
catch (Exception)
{
return false;
}
}
}
And in your controller:
[DemoAuthorize]
public class ValuesController : ApiController{
Here is a link on other custom implemenation for WebApi Authorizations:
http://www.piotrwalat.net/basic-http-authentication-in-asp-net-web-api-using-membership-provider/
How to add button in ActionBar(Android)?
An activity populates the ActionBar in its onCreateOptionsMenu()
method.
Instead of using setcustomview()
, just override onCreateOptionsMenu
like this:
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.mainmenu, menu);
return true;
}
If an actions in the ActionBar is selected, the onOptionsItemSelected()
method is called. It receives the selected action as parameter. Based on this information you code can decide what to do for example:
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menuitem1:
Toast.makeText(this, "Menu Item 1 selected", Toast.LENGTH_SHORT).show();
break;
case R.id.menuitem2:
Toast.makeText(this, "Menu item 2 selected", Toast.LENGTH_SHORT).show();
break;
}
return true;
}
Remove HTML tags from string including   in C#
I took @Ravi Thapliyal's code and made a method: It is simple and might not clean everything, but so far it is doing what I need it to do.
public static string ScrubHtml(string value) {
var step1 = Regex.Replace(value, @"<[^>]+>| ", "").Trim();
var step2 = Regex.Replace(step1, @"\s{2,}", " ");
return step2;
}
Update statement with inner join on Oracle
Oracle base has a good run down on this.
https://oracle-base.com/articles/misc/updates-based-on-queries
From this link - I used a modification of the above query which did not work for me (the answer from mathguy which uses rowid)
MERGE /*+ APPEND PARALLEL(8) */ INTO dest_table tt
USING source_table st
ON (tt.identifier = st.identifier)
WHEN MATCHED THEN
UPDATE SET tt.number = st.number;
Here I have two tables: source and dest. They both have a varchar field in common and I am adding the source identify field (PK) into the dest table.
Access item in a list of lists
This code will print each individual number:
for myList in [[10,13,17],[3,5,1],[13,11,12]]:
for item in myList:
print(item)
Or for your specific use case:
((50 - List1[0][0]) + List1[0][1]) - List1[0][2]
How to check if a process id (PID) exists
You have two ways:
Lets start by looking for a specific application in my laptop:
[root@pinky:~]# ps fax | grep mozilla
3358 ? S 0:00 \_ /bin/sh /usr/lib/firefox-3.5/run-mozilla.sh /usr/lib/firefox-3.5/firefox
16198 pts/2 S+ 0:00 \_ grep mozilla
All examples now will look for PID 3358.
First way: Run "ps aux" and grep for the PID in the second column. In this example I look for firefox, and then for it's PID:
[root@pinky:~]# ps aux | awk '{print $2 }' | grep 3358
3358
So your code will be:
if [ ps aux | awk '{print $2 }' | grep -q $PID 2> /dev/null ]; then
kill $PID
fi
Second way: Just look for something in the /proc/$PID
directory. I am using "exe" in this example, but you can use anything else.
[root@pinky:~]# ls -l /proc/3358/exe
lrwxrwxrwx. 1 elcuco elcuco 0 2010-06-15 12:33 /proc/3358/exe -> /bin/bash
So your code will be:
if [ -f /proc/$PID/exe ]; then
kill $PID
fi
BTW: whats wrong with kill -9 $PID || true
?
EDIT:
After thinking about it for a few months.. (about 24...) the original idea I gave here is a nice hack, but highly unportable. While it teaches a few implementation details of Linux, it will fail to work on Mac, Solaris or *BSD. It may even fail on future Linux kernels. Please - use "ps" as described in other responses.
How to add checkboxes to JTABLE swing
1) JTable knows JCheckbox with built-in Boolean TableCellRenderers and TableCellEditor by default, then there is contraproductive declare something about that,
2) AbstractTableModel should be useful, where is in the JTable
required to reduce/restrict/change nested and inherits methods by default implemented in the DefaultTableModel
,
3) consider using DefaultTableModel
, (if you are not sure about how to works) instead of AbstractTableModel
,
could be generated from simple code:
import javax.swing.*;
import javax.swing.table.*;
public class TableCheckBox extends JFrame {
private static final long serialVersionUID = 1L;
private JTable table;
public TableCheckBox() {
Object[] columnNames = {"Type", "Company", "Shares", "Price", "Boolean"};
Object[][] data = {
{"Buy", "IBM", new Integer(1000), new Double(80.50), false},
{"Sell", "MicroSoft", new Integer(2000), new Double(6.25), true},
{"Sell", "Apple", new Integer(3000), new Double(7.35), true},
{"Buy", "Nortel", new Integer(4000), new Double(20.00), false}
};
DefaultTableModel model = new DefaultTableModel(data, columnNames);
table = new JTable(model) {
private static final long serialVersionUID = 1L;
/*@Override
public Class getColumnClass(int column) {
return getValueAt(0, column).getClass();
}*/
@Override
public Class getColumnClass(int column) {
switch (column) {
case 0:
return String.class;
case 1:
return String.class;
case 2:
return Integer.class;
case 3:
return Double.class;
default:
return Boolean.class;
}
}
};
table.setPreferredScrollableViewportSize(table.getPreferredSize());
JScrollPane scrollPane = new JScrollPane(table);
getContentPane().add(scrollPane);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
TableCheckBox frame = new TableCheckBox();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.pack();
frame.setLocation(150, 150);
frame.setVisible(true);
}
});
}
}
jQuery: Get height of hidden element in jQuery
Here's a script I wrote to handle all of jQuery's dimension methods for hidden elements, even descendants of hidden parents. Note that, of course, there's a performance hit using this.
// Correctly calculate dimensions of hidden elements
(function($) {
var originals = {},
keys = [
'width',
'height',
'innerWidth',
'innerHeight',
'outerWidth',
'outerHeight',
'offset',
'scrollTop',
'scrollLeft'
],
isVisible = function(el) {
el = $(el);
el.data('hidden', []);
var visible = true,
parents = el.parents(),
hiddenData = el.data('hidden');
if(!el.is(':visible')) {
visible = false;
hiddenData[hiddenData.length] = el;
}
parents.each(function(i, parent) {
parent = $(parent);
if(!parent.is(':visible')) {
visible = false;
hiddenData[hiddenData.length] = parent;
}
});
return visible;
};
$.each(keys, function(i, dimension) {
originals[dimension] = $.fn[dimension];
$.fn[dimension] = function(size) {
var el = $(this[0]);
if(
(
size !== undefined &&
!(
(dimension == 'outerHeight' ||
dimension == 'outerWidth') &&
(size === true || size === false)
)
) ||
isVisible(el)
) {
return originals[dimension].call(this, size);
}
var hiddenData = el.data('hidden'),
topHidden = hiddenData[hiddenData.length - 1],
topHiddenClone = topHidden.clone(true),
topHiddenDescendants = topHidden.find('*').andSelf(),
topHiddenCloneDescendants = topHiddenClone.find('*').andSelf(),
elIndex = topHiddenDescendants.index(el[0]),
clone = topHiddenCloneDescendants[elIndex],
ret;
$.each(hiddenData, function(i, hidden) {
var index = topHiddenDescendants.index(hidden);
$(topHiddenCloneDescendants[index]).show();
});
topHidden.before(topHiddenClone);
if(dimension == 'outerHeight' || dimension == 'outerWidth') {
ret = $(clone)[dimension](size ? true : false);
} else {
ret = $(clone)[dimension]();
}
topHiddenClone.remove();
return ret;
};
});
})(jQuery);
Create the perfect JPA entity
My 2 cents addition to the answers here are:
With reference to Field or Property access (away from performance considerations) both are legitimately accessed by means of getters and setters, thus, my model logic can set/get them in the same manner.
The difference comes to play when the persistence runtime provider (Hibernate, EclipseLink or else) needs to persist/set some record in Table A which has a foreign key referring to some column in Table B. In case of a Property access type, the persistence runtime system uses my coded setter method to assign the cell in Table B column a new value. In case of a Field access type, the persistence runtime system sets the cell in Table B column directly.
This difference is not of importance in the context of a uni-directional relationship, yet it is a MUST to use my own coded setter method (Property access type) for a bi-directional relationship provided the setter method is well designed to account for consistency. Consistency is a critical issue for bi-directional relationships refer to this link for a simple example for a well-designed setter.
With reference to Equals/hashCode: It is impossible to use the Eclipse auto-generated Equals/hashCode methods for entities participating in a bi-directional relationship, otherwise they will have a circular reference resulting in a stackoverflow Exception. Once you try a bidirectional relationship (say OneToOne) and auto-generate Equals() or hashCode() or even toString() you will get caught in this stackoverflow exception.
how to display employee names starting with a and then b in sql
Here what I understood from the question is starting with "a " and then "b"
ex:
So there should be two conditions and both should be true means you cant use "OR" operator
Ordered by is not not compulsory but its good if you use.
Select e_name from emp
where e_name like 'a%' AND e_name like '_b%'
Ordered by e_name
WordPress asking for my FTP credentials to install plugins
The easiest way to solve this problem is add the following FTP information to your wp-config.php
define('FS_METHOD', 'direct');
define('FTP_BASE', '/usr/home/username/public_html/my-site.example.com/wordpress/');
define('FTP_CONTENT_DIR', '/usr/home/username/public_html/my-site.example.com/wordpress/wp-content/');
define('FTP_PLUGIN_DIR ', '/usr/home/username/public_html/my-site.example.com/wordpress/wp-content/plugins/');
FTP_BASE is the full path to the "base"(ABSPATH) folder of the WordPress installation
FTP_CONTENT_DIR is the full path to the wp-content folder of the WordPress installation.
FTP_PLUGIN_DIR is the full path to the plugins folder of the WordPress installation.
Firebase cloud messaging notification not received by device
In my case, I noticed mergedmanifest was missing the receiver. So I had to include:
<receiver
android:name="com.google.firebase.iid.FirebaseInstanceIdReceiver"
android:exported="true"
android:permission="com.google.android.c2dm.permission.SEND" >
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
</intent-filter>
</receiver>
Going from MM/DD/YYYY to DD-MMM-YYYY in java
Try this,
Date currDate = new Date();
DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
String strCurrDate = dateFormat.format(currDate);
System.out.println("strCurrDate->"+strCurrDate);
android set button background programmatically
For not changing the size of button on setting the background color:
button.getBackground().setColorFilter(button.getContext().getResources().getColor(R.color.colorAccent), PorterDuff.Mode.MULTIPLY);
this didn't change the size of the button and works with the old android versions too.
Creating an abstract class in Objective-C
Just riffing on @Barry Wark's answer above (and updating for iOS 4.3) and leaving this for my own reference:
#define mustOverride() @throw [NSException exceptionWithName:NSInvalidArgumentException reason:[NSString stringWithFormat:@"%s must be overridden in a subclass/category", __PRETTY_FUNCTION__] userInfo:nil]
#define methodNotImplemented() mustOverride()
then in your methods you can use this
- (void) someMethod {
mustOverride(); // or methodNotImplemented(), same thing
}
Notes: Not sure if making a macro look like a C function is a good idea or not, but I'll keep it until schooled to the contrary. I think it's more correct to use NSInvalidArgumentException
(rather than NSInternalInconsistencyException
) since that's what the runtime system throws in response to doesNotRecognizeSelector
being called (see NSObject
docs).
How to catch curl errors in PHP
If CURLOPT_FAILONERROR
is false
, http errors will not trigger curl
errors.
<?php
if (@$_GET['curl']=="yes") {
header('HTTP/1.1 503 Service Temporarily Unavailable');
} else {
$ch=curl_init($url = "http://".$_SERVER['SERVER_NAME'].$_SERVER['PHP_SELF']."?curl=yes");
curl_setopt($ch, CURLOPT_FAILONERROR, true);
$response=curl_exec($ch);
$http_status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
$curl_errno= curl_errno($ch);
if ($http_status==503)
echo "HTTP Status == 503 <br/>";
echo "Curl Errno returned $curl_errno <br/>";
}
Copy data from another Workbook through VBA
I had the same question but applying the provided solutions changed the file to write in. Once I selected the new excel file, I was also writing in that file and not in my original file. My solution for this issue is below:
Sub GetData()
Dim excelapp As Application
Dim source As Workbook
Dim srcSH1 As Worksheet
Dim sh As Worksheet
Dim path As String
Dim nmr As Long
Dim i As Long
nmr = 20
Set excelapp = New Application
With Application.FileDialog(msoFileDialogOpen)
.AllowMultiSelect = False
.Filters.Add "Excel Files", "*.xlsx; *.xlsm; *.xls; *.xlsb", 1
.Show
path = .SelectedItems.Item(1)
End With
Set source = excelapp.Workbooks.Open(path)
Set srcSH1 = source.Worksheets("Sheet1")
Set sh = Sheets("Sheet1")
For i = 1 To nmr
sh.Cells(i, "A").Value = srcSH1.Cells(i, "A").Value
Next i
End Sub
With excelapp
a new application will be called. The with
block sets the path for the external file. Finally, I set the external Workbook with source
and srcSH1
as a Worksheet within the external sheet.
Handling errors in Promise.all
You would need to know how to identify an error in your results. If you do not have a standard expected error, I suggest that you run a transformation on each error in the catch block that makes it identifiable in your results.
try {
let resArray = await Promise.all(
state.routes.map(route => route.handler.promiseHandler().catch(e => e))
);
// in catch(e => e) you can transform your error to a type or object
// that makes it easier for you to identify whats an error in resArray
// e.g. if you expect your err objects to have e.type, you can filter
// all errors in the array eg
// let errResponse = resArray.filter(d => d && d.type === '<expected type>')
// let notNullResponse = resArray.filter(d => d)
} catch (err) {
// code related errors
}
caching JavaScript files
I am heavily tempted to close this as a duplicate; this question appears to be answered in many different ways all over the site:
ImportError: No module named sqlalchemy
So here is an idea!
Since it seemed to work somewhere else.
install python-virtualenv
and optionally you can install virtualenv-wrapper (which is pretty cool to create projects and so on)
In each env, you might have different versions of eggs. In other word, you could have sqlalchemy 1 and sqlaclhemy 1.5 in two different envs and they won't conflict with each others. It seems that you have a problem with your currently installed eggs.
So here we go:
virtualenv --no-site-packages foo
source foo/bin/activate
The parameter --no-site-packages will create a virtualenv and not use the packages already installed on your computer. It's pretty much like a bare python install.
source foo/bin/activate
loads the virtualenv.
It's not that really userfriendly. And that's why http://www.doughellmann.com/projects/virtualenvwrapper/ exists.
That said, you should see somthing like thant in your terminal "(foo)user@domain$:" once your virtualenv is activated. It means that you can go on!
Then you have to do.
python setup.py develop
of your project. It should download and install dependencies of your project in the virtualenv located in foo
. If you need to install anything else, please use pip
or easy_install
without using sudo
. When using virtualenv, you almost never need to use sudo
. Sudo will install package in your global python install while it's not required and not really desirable.
If something happens in your virtualenv, you can always delete it and create a new one. This is no big deal. No need to mess with anything. Doesn't work? start over, do pip install -U
if needed, define the versions if needed and so on.
Last but not least, in the other answers, it seems that the import changed. If the new versions for flask-sqlalchemy is located somewhere else, you should update your import or install the version you used to use.
matplotlib: Group boxplots
Just to add to the conversation, I have found a more elegant way to change the color of the box plot by iterating over the dictionary of the object itself
import numpy as np
import matplotlib.pyplot as plt
def color_box(bp, color):
# Define the elements to color. You can also add medians, fliers and means
elements = ['boxes','caps','whiskers']
# Iterate over each of the elements changing the color
for elem in elements:
[plt.setp(bp[elem][idx], color=color) for idx in xrange(len(bp[elem]))]
return
a = np.random.uniform(0,10,[100,5])
bp = plt.boxplot(a)
color_box(bp, 'red')
Cheers!
How to get the jQuery $.ajax error response text?
you can try it too:
$(document).ajaxError(
function (event, jqXHR, ajaxSettings, thrownError) {
alert('[event:' + event + '], [jqXHR:' + jqXHR + '], [ajaxSettings:' + ajaxSettings + '], [thrownError:' + thrownError + '])');
});
Benefits of EBS vs. instance-store (and vice-versa)
Eric pretty much nailed it. We (Bitnami) are a popular provider of free AMIs for popular applications and development frameworks (PHP, Joomla, Drupal, you get the idea). I can tell you that EBS-backed AMIs are significantly more popular than S3-backed. In general I think s3-backed instances are used for distributed, time-limited jobs (for example, large scale processing of data) where if one machine fails, another one is simply spinned up. EBS-backed AMIS tend to be used for 'traditional' server tasks, such as web or database servers that keep state locally and thus require the data to be available in the case of crashing.
One aspect I did not see mentioned is the fact that you can take snapshots of an EBS-backed instance while running, effectively allowing you to have very cost-effective backups of your infrastructure (the snapshots are block-based and incremental)
Textarea onchange detection
The best thing that you can do is to set a function to be called on a given amount of time and this function to check the contents of your textarea.
self.setInterval('checkTextAreaValue()', 50);
iterating over and removing from a map
As of Java 8 you could do this as follows:
map.entrySet().removeIf(e -> <boolean expression>);
Oracle Docs: entrySet()
The set is backed by the map, so changes to the map are reflected in the set, and vice-versa
Learning Regular Expressions
The most important part is the concepts. Once you understand how the building blocks work, differences in syntax amount to little more than mild dialects. A layer on top of your regular expression engine's syntax is the syntax of the programming language you're using. Languages such as Perl remove most of this complication, but you'll have to keep in mind other considerations if you're using regular expressions in a C program.
If you think of regular expressions as building blocks that you can mix and match as you please, it helps you learn how to write and debug your own patterns but also how to understand patterns written by others.
Start simple
Conceptually, the simplest regular expressions are literal characters. The pattern N
matches the character 'N'.
Regular expressions next to each other match sequences. For example, the pattern Nick
matches the sequence 'N' followed by 'i' followed by 'c' followed by 'k'.
If you've ever used grep
on Unix—even if only to search for ordinary looking strings—you've already been using regular expressions! (The re
in grep
refers to regular expressions.)
Order from the menu
Adding just a little complexity, you can match either 'Nick' or 'nick' with the pattern [Nn]ick
. The part in square brackets is a character class, which means it matches exactly one of the enclosed characters. You can also use ranges in character classes, so [a-c]
matches either 'a' or 'b' or 'c'.
The pattern .
is special: rather than matching a literal dot only, it matches any character†. It's the same conceptually as the really big character class [-.?+%$A-Za-z0-9...]
.
Think of character classes as menus: pick just one.
Helpful shortcuts
Using .
can save you lots of typing, and there are other shortcuts for common patterns. Say you want to match a digit: one way to write that is [0-9]
. Digits are a frequent match target, so you could instead use the shortcut \d
. Others are \s
(whitespace) and \w
(word characters: alphanumerics or underscore).
The uppercased variants are their complements, so \S
matches any non-whitespace character, for example.
Once is not enough
From there, you can repeat parts of your pattern with quantifiers. For example, the pattern ab?c
matches 'abc' or 'ac' because the ?
quantifier makes the subpattern it modifies optional. Other quantifiers are
*
(zero or more times)
+
(one or more times)
{n}
(exactly n times)
{n,}
(at least n times)
{n,m}
(at least n times but no more than m times)
Putting some of these blocks together, the pattern [Nn]*ick
matches all of
- ick
- Nick
- nick
- Nnick
- nNick
- nnick
- (and so on)
The first match demonstrates an important lesson: *
always succeeds! Any pattern can match zero times.
A few other useful examples:
[0-9]+
(and its equivalent \d+
) matches any non-negative integer
\d{4}-\d{2}-\d{2}
matches dates formatted like 2019-01-01
Grouping
A quantifier modifies the pattern to its immediate left. You might expect 0abc+0
to match '0abc0', '0abcabc0', and so forth, but the pattern immediately to the left of the plus quantifier is c
. This means 0abc+0
matches '0abc0', '0abcc0', '0abccc0', and so on.
To match one or more sequences of 'abc' with zeros on the ends, use 0(abc)+0
. The parentheses denote a subpattern that can be quantified as a unit. It's also common for regular expression engines to save or "capture" the portion of the input text that matches a parenthesized group. Extracting bits this way is much more flexible and less error-prone than counting indices and substr
.
Alternation
Earlier, we saw one way to match either 'Nick' or 'nick'. Another is with alternation as in Nick|nick
. Remember that alternation includes everything to its left and everything to its right. Use grouping parentheses to limit the scope of |
, e.g., (Nick|nick)
.
For another example, you could equivalently write [a-c]
as a|b|c
, but this is likely to be suboptimal because many implementations assume alternatives will have lengths greater than 1.
Escaping
Although some characters match themselves, others have special meanings. The pattern \d+
doesn't match backslash followed by lowercase D followed by a plus sign: to get that, we'd use \\d\+
. A backslash removes the special meaning from the following character.
Greediness
Regular expression quantifiers are greedy. This means they match as much text as they possibly can while allowing the entire pattern to match successfully.
For example, say the input is
"Hello," she said, "How are you?"
You might expect ".+"
to match only 'Hello,' and will then be surprised when you see that it matched from 'Hello' all the way through 'you?'.
To switch from greedy to what you might think of as cautious, add an extra ?
to the quantifier. Now you understand how \((.+?)\)
, the example from your question works. It matches the sequence of a literal left-parenthesis, followed by one or more characters, and terminated by a right-parenthesis.
If your input is '(123) (456)', then the first capture will be '123'. Non-greedy quantifiers want to allow the rest of the pattern to start matching as soon as possible.
(As to your confusion, I don't know of any regular-expression dialect where ((.+?))
would do the same thing. I suspect something got lost in transmission somewhere along the way.)
Anchors
Use the special pattern ^
to match only at the beginning of your input and $
to match only at the end. Making "bookends" with your patterns where you say, "I know what's at the front and back, but give me everything between" is a useful technique.
Say you want to match comments of the form
-- This is a comment --
you'd write ^--\s+(.+)\s+--$
.
Build your own
Regular expressions are recursive, so now that you understand these basic rules, you can combine them however you like.
Tools for writing and debugging regexes:
Books
Free resources
Footnote
†: The statement above that .
matches any character is a simplification for pedagogical purposes that is not strictly true. Dot matches any character except newline, "\n"
, but in practice you rarely expect a pattern such as .+
to cross a newline boundary. Perl regexes have a /s
switch and Java Pattern.DOTALL
, for example, to make .
match any character at all. For languages that don't have such a feature, you can use something like [\s\S]
to match "any whitespace or any non-whitespace", in other words anything.
Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?
LINQ-to-SQL is a remarkable piece of technology that is very simple to use, and by and large generates very good queries to the back end. LINQ-to-EF was slated to supplant it, but historically has been extremely clunky to use and generated far inferior SQL. I don't know the current state of affairs, but Microsoft promised to migrate all the goodness of L2S into L2EF, so maybe it's all better now.
Personally, I have a passionate dislike of ORM tools (see my diatribe here for the details), and so I see no reason to favour L2EF, since L2S gives me all I ever expect to need from a data access layer. In fact, I even think that L2S features such as hand-crafted mappings and inheritance modeling add completely unnecessary complexity. But that's just me. ;-)
PHP using Gettext inside <<<EOF string
As far as I can see in the manual, it is not possible to call functions inside HEREDOC strings. A cumbersome way would be to prepare the words beforehand:
<?php
$world = _("World");
$str = <<<EOF
<p>Hello</p>
<p>$world</p>
EOF;
echo $str;
?>
a workaround idea that comes to mind is building a class with a magic getter method.
You would declare a class like this:
class Translator
{
public function __get($name) {
return _($name); // Does the gettext lookup
}
}
Initialize an object of the class at some point:
$translate = new Translator();
You can then use the following syntax to do a gettext lookup inside a HEREDOC block:
$str = <<<EOF
<p>Hello</p>
<p>{$translate->World}</p>
EOF;
echo $str;
?>
$translate->World
will automatically be translated to the gettext lookup thanks to the magic getter method.
To use this method for words with spaces or special characters (e.g. a gettext entry named Hello World!!!!!!
, you will have to use the following notation:
$translate->{"Hello World!!!!!!"}
This is all untested but should work.
Update: As @mario found out, it is possible to call functions from HEREDOC strings after all. I think using getters like this is a sleek solution, but using a direct function call may be easier. See the comments on how to do this.
There is already an open DataReader associated with this Command which must be closed first
In my case, I had to set the MultipleActiveResultSets
to True
in the connection string.
Then it appeared another error (the real one) about not being able to run 2 (SQL) commands at the same time over the same data context! (EF Core, Code first)
So the solution for me was to look for any other asynchronous command execution and turn them to synchronous, as I had just one DbContext for both commands.
I hope it helps you
What does "both" mean in <div style="clear:both">
Description of the possible values:
left
: No floating elements allowed on the left side
right
: No floating elements allowed on the right side
both
: No floating elements allowed on either the left or the right side
none
: Default. Allows floating elements on both sides
inherit
: Specifies that the value of the clear property should be inherited from the parent element
Source: w3schools.com
Valid content-type for XML, HTML and XHTML documents
HTML: text/html
, full-stop.
XHTML: application/xhtml+xml
, or only if following HTML compatbility guidelines, text/html
. See the W3 Media Types Note.
XML: text/xml
, application/xml
(RFC 2376).
There are also many other media types based around XML, for example application/rss+xml
or image/svg+xml
. It's a safe bet that any unrecognised but registered ending in +xml
is XML-based. See the IANA list for registered media types ending in +xml
.
(For unregistered x-
types, all bets are off, but you'd hope +xml
would be respected.)
What is the difference between a cer, pvk, and pfx file?
I actually came across something like this not too long ago... check it out over on msdn (see the first answer)
in summary:
.cer - certificate stored in the X.509 standard format. This certificate contains information about the certificate's owner... along with public and private keys.
.pvk - files are used to store private keys for code signing. You can also create a certificate based on .pvk private key file.
.pfx - stands for personal exchange format. It is used to exchange public and private objects in a single file. A pfx file can be created from .cer file. Can also be used to create a Software Publisher Certificate.
I summarized the info from the page based on the suggestion from the comments.
Adding Python Path on Windows 7
- Hold Win and press Pause.
- Click Advanced System Settings.
- Click Environment Variables.
- Append
;C:\python27
to the Path
variable.
- Restart Command Prompt.
Taking pictures with camera on Android programmatically
Take and store image in desired folder
//Global Variables
private static final int CAMERA_IMAGE_REQUEST = 101;
private String imageName;
Take picture function
public void captureImage() {
// Creating folders for Image
String imageFolderPath = Environment.getExternalStorageDirectory().toString()
+ "/AutoFare";
File imagesFolder = new File(imageFolderPath);
imagesFolder.mkdirs();
// Generating file name
imageName = new Date().toString() + ".png";
// Creating image here
Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(new File(imageFolderPath, imageName)));
startActivityForResult(takePictureIntent,
CAMERA_IMAGE_REQUEST);
}
Broadcast new image added otherwise pic will not be visible in image gallery
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == Activity.RESULT_OK && requestCode == CAMERA_IMAGE_REQUEST) {
Toast.makeText(getActivity(), "Success",
Toast.LENGTH_SHORT).show();
//Scan new image added
MediaScannerConnection.scanFile(getActivity(), new String[]{new File(Environment.getExternalStorageDirectory()
+ "/AutoFare/" + imageName).getPath()}, new String[]{"image/png"}, null);
// Work in few phones
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
getActivity().sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse(Environment.getExternalStorageDirectory()
+ "/AutoFare/" + imageName)));
} else {
getActivity().sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse(Environment.getExternalStorageDirectory()
+ "/AutoFare/" + imageName)));
}
} else {
Toast.makeText(getActivity(), "Take Picture Failed or canceled",
Toast.LENGTH_SHORT).show();
}
}
Permissions
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
Pass by Reference / Value in C++
I'm not sure if I understand your question correctly. It is a bit unclear. However, what might be confusing you is the following:
When passing by reference, a reference to the same object is passed to the function being called. Any changes to the object will be reflected in the original object and hence the caller will see it.
When passing by value, the copy constructor will be called. The default copy constructor will only do a shallow copy, hence, if the called function modifies an integer in the object, this will not be seen by the calling function, but if the function changes a data structure pointed to by a pointer within the object, then this will be seen by the caller due to the shallow copy.
I might have mis-understood your question, but I thought I would give it a stab anyway.
What are the differences between Abstract Factory and Factory design patterns?
- My first question is about the abstract factory. Is its role to allow you to create families of concrete objects in (that can depend on what specific factory you use) rather than just a single concrete object?
Yes. The intent of Abstract Factory is:
Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
- Does the abstract factory only return one very large object or many objects depending on what methods you call?
Ideally it should return one object per the method client is invoking.
- My understanding is that the factory method pattern has a Creator interface that will make the ConcreteCreator be in charge of knowing which ConcreteProduct to instantiate. Is this what it means by using inheritance to handle object instantiation?
Yes. Factory method uses inheritance.
- Abstract Factory pattern delegate the responsibility of object instantiation to another object via composition? What does this mean?
AbstractFactory defines a FactoryMethod and ConcreteFactory is responsible for building a ConcreteProduct. Just follow through the code example in this article.
You can find more details in related SE posts:
What is the basic difference between the Factory and Abstract Factory Patterns?
Design Patterns: Factory vs Factory method vs Abstract Factory
Gradle to execute Java class (without modifying build.gradle)
You can parameterise it and pass gradle clean build -Pprokey=goodbye
task choiceMyMainClass(type: JavaExec) {
group = "Execution"
description = "Run Option main class with JavaExecTask"
classpath = sourceSets.main.runtimeClasspath
if (project.hasProperty('prokey')){
if (prokey == 'hello'){
main = 'com.sam.home.HelloWorld'
}
else if (prokey == 'goodbye'){
main = 'com.sam.home.GoodBye'
}
} else {
println 'Invalid value is enterrd';
// println 'Invalid value is enterrd'+ project.prokey;
}
Basic authentication for REST API using spring restTemplate
There are multiple ways to add the basic HTTP authentication to the RestTemplate
.
1. For a single request
try {
// request url
String url = "https://jsonplaceholder.typicode.com/posts";
// create auth credentials
String authStr = "username:password";
String base64Creds = Base64.getEncoder().encodeToString(authStr.getBytes());
// create headers
HttpHeaders headers = new HttpHeaders();
headers.add("Authorization", "Basic " + base64Creds);
// create request
HttpEntity request = new HttpEntity(headers);
// make a request
ResponseEntity<String> response = new RestTemplate().exchange(url, HttpMethod.GET, request, String.class);
// get JSON response
String json = response.getBody();
} catch (Exception ex) {
ex.printStackTrace();
}
If you are using Spring 5.1
or higher, it is no longer required to manually set the authorization header. Use headers.setBasicAuth()
method instead:
// create headers
HttpHeaders headers = new HttpHeaders();
headers.setBasicAuth("username", "password");
2. For a group of requests
@Service
public class RestService {
private final RestTemplate restTemplate;
public RestService(RestTemplateBuilder restTemplateBuilder) {
this.restTemplate = restTemplateBuilder
.basicAuthentication("username", "password")
.build();
}
// use `restTemplate` instance here
}
3. For each and every request
@Bean
RestOperations restTemplateBuilder(RestTemplateBuilder restTemplateBuilder) {
return restTemplateBuilder.basicAuthentication("username", "password").build();
}
I hope it helps!
How to use addTarget method in swift 3
The poster's second comment from September 21st is spot on. For those who may be coming to this thread later with the same problem as the poster, here is a brief explanation. The other answers are good to keep in mind, but do not address the common issue encountered by this code.
In Swift, declarations made with the let
keyword are constants. Of course if you were going to add items to an array, the array can't be declared as a constant, but a segmented control should be fine, right?! Not if you reference the completed segmented control in its declaration.
Referencing the object (in this case a UISegmentedControl
, but this also happens with UIButton
) in its declaration when you say .addTarget
and let the target be self
, things crash. Why? Because self
is in the midst of being defined. But we do want to define behaviour as part of the object... Declare it lazily as a variable with var
. The lazy
fools the compiler into thinking that self
is well defined - it silences your compiler from caring at the time of declaration. Lazily declared variables don't get set until they are first called. So in this situation, lazy
lets you use the notion of self
without issue while you set up the object, and then when your object gets a .touchUpInside
or .valueChanged
or whatever your 3rd argument is in your .addTarget()
, THEN it calls on the notion of self
, which at that point is fully established and totally prepared to be a valid target. So it lets you be lazy in declaring your variable. In cases like these, I think they could give us a keyword like necessary
, but it is generally seen as a lazy, sloppy practice and you don't want to use it all over your code, though it may have its place in this sort of situation. What it
There is no lazy let
in Swift (no lazy
for constants).
Here is the Apple documentation on lazy.
Here is the Apple on variables and constants. There is a little more in their Language Reference under Declarations.
Set multiple system properties Java command line
You may be able to use the JAVA_TOOL_OPTIONS
environment variable to set options. It worked for me with Rasbian. See Environment Variables and System Properties which has this to say:
In many environments, the command line is not readily accessible to
start the application with the necessary command-line options.
This often happens with applications that use embedded VMs (meaning
they use the Java Native Interface (JNI) Invocation API to start the
VM), or where the startup is deeply nested in scripts. In these
environments the JAVA_TOOL_OPTIONS environment variable can be useful
to augment a command line.
When this environment variable is set, the JNI_CreateJavaVM function
(in the JNI Invocation API), the JNI_CreateJavaVM function adds the
value of the environment variable to the options supplied in its
JavaVMInitArgs argument.
However this environment variable use may be disabled for security reasons.
In some cases, this option is disabled for security reasons. For
example, on the Oracle Solaris operating system, this option is
disabled when the effective user or group ID differs from the real ID.
See this example showing the difference between specifying on the command line versus using the JAVA_TOOL_OPTIONS
environment variable.
What is a stack trace, and how can I use it to debug my application errors?
The other posts describe what a stack trace is, but it can still be hard to work with.
If you get a stack trace and want to trace the cause of the exception, a good start point in understanding it is to use the Java Stack Trace Console in Eclipse. If you use another IDE there may be a similar feature, but this answer is about Eclipse.
First, ensure that you have all of your Java sources accessible in an Eclipse project.
Then in the Java perspective, click on the Console tab (usually at the bottom). If the Console view is not visible, go to the menu option Window -> Show View and select Console.
Then in the console window, click on the following button (on the right)
and then select Java Stack Trace Console from the drop-down list.
Paste your stack trace into the console. It will then provide a list of links into your source code and any other source code available.
This is what you might see (image from the Eclipse documentation):
The most recent method call made will be the top of the stack, which is the top line (excluding the message text). Going down the stack goes back in time. The second line is the method that calls the first line, etc.
If you are using open-source software, you might need to download and attach to your project the sources if you want to examine. Download the source jars, in your project, open the Referenced Libraries folder to find your jar for your open-source module (the one with the class files) then right click, select Properties and attach the source jar.
What is a 'workspace' in Visual Studio Code?
Although the question is asking "what is a workspace?", I feel that the source of confusion is the expectation that workspaces should behave more like "projects" in other editors.
So, I to help all the people landing here because of this confusion, I wanted to post the following plugin for VS Code (not mine), "Project Manager": https://marketplace.visualstudio.com/items?itemName=alefragnani.project-manager
It has a nice UI for managing (saving and opening) single-folder projects:
Save Projects:
Open projects with the palette:
See the current project in the status bar (click to open project palette):
Access projects in the sidebar:
Create instance of generic type in Java?
Here's an implementation of createContents
that uses TypeTools to resolve the raw class represented by E
:
E createContents() throws Exception {
return TypeTools.resolveRawArgument(SomeContainer.class, getClass()).newInstance();
}
This approach only works if SomeContainer
is subclassed so the actual value of E
is captured in a type definition:
class SomeStringContainer extends SomeContainer<String>
Otherwise the value of E is erased at runtime and is not recoverable.
How to "wait" a Thread in Android
You need the sleep
method of the Thread
class.
public static void sleep (long time)
Causes the thread which sent this message to sleep for the given interval of time (given in milliseconds). The precision is not guaranteed - the Thread may sleep more or less than requested.
Parameters
time
The time to sleep in milliseconds.
How do I store the select column in a variable?
select @EmpID = ID from dbo.Employee
Or
set @EmpID =(select id from dbo.Employee)
Note that the select query might return more than one value or rows. so you can write a select query that must return one row.
If you would like to add more columns to one variable(MS SQL), there is an option to use table defined variable
DECLARE @sampleTable TABLE(column1 type1)
INSERT INTO @sampleTable
SELECT columnsNumberEqualInsampleTable FROM .. WHERE ..
As table type variable do not exist in Oracle and others, you would have to define it:
DECLARE TYPE type_name IS TABLE OF (column_type | variable%TYPE | table.column%TYPE [NOT NULL] INDEX BY BINARY INTEGER;
-- Then to declare a TABLE variable of this type: variable_name type_name;
-- Assigning values to a TABLE variable: variable_name(n).field_name := 'some text'
;
-- Where 'n' is the index value
Excel VBA select range at last row and column
Is this what you are trying? I have commented the code so that you will not have any problem understanding it.
Sub Sample()
Dim ws As Worksheet
Dim lRow As Long, lCol As Long
Dim rng As Range
'~~> Set this to the relevant worksheet
Set ws = [Sheet1]
With ws
'~~> Get the last row and last column
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
lCol = .Cells(1, .Columns.Count).End(xlToLeft).Column
'~~> Set the range
Set rng = .Range(.Cells(lRow, 1), .Cells(lRow, lCol))
With rng
Debug.Print .Address
'
'~~> What ever you want to do with the address
'
End With
End With
End Sub
BTW I am assuming that LastRow
is the same for all rows and same goes for the columns. If that is not the case then you will have use .Find
to find the Last Row and the Last Column. You might want to see THIS
In Python, is there an elegant way to print a list in a custom format without explicit looping?
In python 3s print function:
lst = [1, 2, 3]
print('My list:', *lst, sep='\n- ')
Output:
My list:
- 1
- 2
- 3
Con: The sep
must be a string, so you can't modify it based on which element you're printing. And you need a kind of header to do this (above it was 'My list:'
).
Pro: You don't have to join()
a list into a string object, which might be advantageous for larger lists. And the whole thing is quite concise and readable.
Join String list elements with a delimiter in one step
If you are using Spring you can use StringUtils.join()
method which also allows you to specify prefix and suffix.
String s = StringUtils.collectionToDelimitedString(fieldRoles.keySet(),
"\n", "<value>", "</value>");
What does --net=host option in Docker command really do?
- you can create your own new network like --net="anyname"
- this is done to isolate the services from different container.
- suppose the same service are running in different containers, but the port mapping
remains same, the first container starts well , but the same service from second container will fail.
so to avoid this, either change the port mappings or create a network.
Detect IE version (prior to v9) in JavaScript
Conditional comments are no longer supported in IE as of Version 10 as noted on the Microsoft reference page.
_x000D_
_x000D_
var ieDetector = function() {_x000D_
var browser = { // browser object_x000D_
_x000D_
verIE: null,_x000D_
docModeIE: null,_x000D_
verIEtrue: null,_x000D_
verIE_ua: null_x000D_
_x000D_
},_x000D_
tmp;_x000D_
_x000D_
tmp = document.documentMode;_x000D_
try {_x000D_
document.documentMode = "";_x000D_
} catch (e) {};_x000D_
_x000D_
browser.isIE = typeof document.documentMode == "number" || eval("/*@cc_on!@*/!1");_x000D_
try {_x000D_
document.documentMode = tmp;_x000D_
} catch (e) {};_x000D_
_x000D_
// We only let IE run this code._x000D_
if (browser.isIE) {_x000D_
browser.verIE_ua =_x000D_
(/^(?:.*?[^a-zA-Z])??(?:MSIE|rv\s*\:)\s*(\d+\.?\d*)/i).test(navigator.userAgent || "") ?_x000D_
parseFloat(RegExp.$1, 10) : null;_x000D_
_x000D_
var e, verTrueFloat, x,_x000D_
obj = document.createElement("div"),_x000D_
_x000D_
CLASSID = [_x000D_
"{45EA75A0-A269-11D1-B5BF-0000F8051515}", // Internet Explorer Help_x000D_
"{3AF36230-A269-11D1-B5BF-0000F8051515}", // Offline Browsing Pack_x000D_
"{89820200-ECBD-11CF-8B85-00AA005B4383}"_x000D_
];_x000D_
_x000D_
try {_x000D_
obj.style.behavior = "url(#default#clientcaps)"_x000D_
} catch (e) {};_x000D_
_x000D_
for (x = 0; x < CLASSID.length; x++) {_x000D_
try {_x000D_
browser.verIEtrue = obj.getComponentVersion(CLASSID[x], "componentid").replace(/,/g, ".");_x000D_
} catch (e) {};_x000D_
_x000D_
if (browser.verIEtrue) break;_x000D_
_x000D_
};_x000D_
verTrueFloat = parseFloat(browser.verIEtrue || "0", 10);_x000D_
browser.docModeIE = document.documentMode ||_x000D_
((/back/i).test(document.compatMode || "") ? 5 : verTrueFloat) ||_x000D_
browser.verIE_ua;_x000D_
browser.verIE = verTrueFloat || browser.docModeIE;_x000D_
};_x000D_
_x000D_
return {_x000D_
isIE: browser.isIE,_x000D_
Version: browser.verIE_x000D_
};_x000D_
_x000D_
}();_x000D_
_x000D_
document.write('isIE: ' + ieDetector.isIE + "<br />");_x000D_
document.write('IE Version Number: ' + ieDetector.Version);
_x000D_
_x000D_
_x000D_
then use:
if((ieDetector.isIE) && (ieDetector.Version <= 9))
{
}
How can I specify a [DllImport] path at runtime?
If all fails, simply put the DLL in the windows\system32
folder . The compiler will find it.
Specify the DLL to load from with: DllImport("user32.dll"...
, set EntryPoint = "my_unmanaged_function"
to import your desired unmanaged function to your C# app:
using System;
using System.Runtime.InteropServices;
class Example
{
// Use DllImport to import the Win32 MessageBox function.
[DllImport ("user32.dll", CharSet = CharSet.Auto)]
public static extern int MessageBox
(IntPtr hWnd, String text, String caption, uint type);
static void Main()
{
// Call the MessageBox function using platform invoke.
MessageBox (new IntPtr(0), "Hello, World!", "Hello Dialog", 0);
}
}
Source and even more DllImport
examples : http://msdn.microsoft.com/en-us/library/aa288468(v=vs.71).aspx
Error Handler - Exit Sub vs. End Sub
Your ProcExit label is your place where you release all the resources whether an error happened or not. For instance:
Public Sub SubA()
On Error Goto ProcError
Connection.Open
Open File for Writing
SomePreciousResource.GrabIt
ProcExit:
Connection.Close
Connection = Nothing
Close File
SomePreciousResource.Release
Exit Sub
ProcError:
MsgBox Err.Description
Resume ProcExit
End Sub
Why do I need to explicitly push a new branch?
I just experienced a further permutation of this issue.
I had a branch named feat/XYZ-1234-some-description
because I was working on Jira issue 1234. During the work I created a new Jira issue to track a smaller piece of work, and when I came to push I decided to push to a branch name with this new issue number in:
git push -u origin feat/XYZ-5678-a-different-description # failed
This gave me the error being discussed in this SO thread. But since I was trying to push to a different branch name from my current branch, my problem was different to the one described here. I ended up renaming my local branch before I could push it:
git branch -m feat/XYZ-1234-some-description feat/XYZ-5678-a-different-description
git push -u origin feat/XYZ-5678-a-different-description # now works
After a bit more reading around I realised that I could have set a src
on the
git push
, either to the current branch name, or just HEAD
if appropriate:
git push -u origin feat/XYZ-1234-some-description:feat/XYZ-5678-a-different-description # also works
Memcached vs. Redis?
This is too long to be posted as a comment to already accepted answer, so I put it as a separate answer
One thing also to consider is whether you expect to have a hard upper memory limit on your cache instance.
Since redis is an nosql database with tons of features and caching is only one option it can be used for, it allocates memory as it needs it — the more objects you put in it, the more memory it uses. The maxmemory
option does not strictly enforces upper memory limit usage. As you work with cache, keys are evicted and expired; chances are your keys are not all the same size, so internal memory fragmentation occurs.
By default redis uses jemalloc memory allocator, which tries its best to be both memory-compact and fast, but it is a general purpose memory allocator and it cannot keep up with lots of allocations and object purging occuring at a high rate. Because of this, on some load patterns redis process can apparently leak memory because of internal fragmentation. For example, if you have a server with 7 Gb RAM and you want to use redis as non-persistent LRU cache, you may find that redis process with maxmemory
set to 5Gb over time would use more and more memory, eventually hitting total RAM limit until out-of-memory killer interferes.
memcached is a better fit to scenario described above, as it manages its memory in a completely different way. memcached allocates one big chunk of memory — everything it will ever need — and then manages this memory by itself, using its own implemented slab allocator. Moreover, memcached tries hard to keep internal fragmentation low, as it actually uses per-slab LRU algorithm, when LRU evictions are done with object size considered.
With that said, memcached still has a strong position in environments, where memory usage has to be enforced and/or be predictable. We've tried to use latest stable redis (2.8.19) as a drop-in non-persistent LRU-based memcached replacement in workload of 10-15k op/s, and it leaked memory A LOT; the same workload was crashing Amazon's ElastiCache redis instances in a day or so because of the same reasons.
Replace substring with another substring C++
Boost String Algorithms Library way:
#include <boost/algorithm/string/replace.hpp>
{ // 1.
string test = "abc def abc def";
boost::replace_all(test, "abc", "hij");
boost::replace_all(test, "def", "klm");
}
{ // 2.
string test = boost::replace_all_copy
( boost::replace_all_copy<string>("abc def abc def", "abc", "hij")
, "def"
, "klm"
);
}
HTTP client timeout and server timeout
go to the url about:config
and paste each line:
network.http.keep-alive.timeout;10
network.http.connection-retry-timeout;10
network.http.pipelining.read-timeout;5
network.http.connection-timeout;10
javascript create empty array of a given size
Try using while
loop, Array.prototype.push()
var myArray = [], X = 3;
while (myArray.length < X) {
myArray.push("")
}
Alternatively, using Array.prototype.fill()
var myArray = Array(3).fill("");
Clone only one branch
You could create a new repo with
git init
and then use
git fetch url-to-repo branchname:refs/remotes/origin/branchname
to fetch just that one branch into a local remote-tracking branch.
Determine command line working directory when running node bin script
Alternatively, if you want to solely obtain the current directory of the current NodeJS script, you could try something simple like this. Note that this will not work in the Node CLI itself:
var fs = require('fs'),
path = require('path');
var dirString = path.dirname(fs.realpathSync(__filename));
// output example: "/Users/jb/workspace/abtest"
console.log('directory to start walking...', dirString);
Efficiently checking if arbitrary object is NaN in Python / numpy / pandas?
pandas.isnull()
(also pd.isna()
, in newer versions) checks for missing values in both numeric and string/object arrays. From the documentation, it checks for:
NaN in numeric arrays, None/NaN in object arrays
Quick example:
import pandas as pd
import numpy as np
s = pd.Series(['apple', np.nan, 'banana'])
pd.isnull(s)
Out[9]:
0 False
1 True
2 False
dtype: bool
The idea of using numpy.nan
to represent missing values is something that pandas
introduced, which is why pandas
has the tools to deal with it.
Datetimes too (if you use pd.NaT
you won't need to specify the dtype)
In [24]: s = Series([Timestamp('20130101'),np.nan,Timestamp('20130102 9:30')],dtype='M8[ns]')
In [25]: s
Out[25]:
0 2013-01-01 00:00:00
1 NaT
2 2013-01-02 09:30:00
dtype: datetime64[ns]``
In [26]: pd.isnull(s)
Out[26]:
0 False
1 True
2 False
dtype: bool
Where is the .NET Framework 4.5 directory?
.NET 4.5 is not a side-by-side version, it replaces the assemblies for 4.0. Much like .NET 3.0, 3.5 and 3.5SP1 replaced the assemblies for 2.0. And added some new ones. The CLR version is still 4.0.30319. You only care about the reference assemblies, they are in c:\program files\reference assemblies.
trying to animate a constraint in swift
It's very important to point out that view.layoutIfNeeded()
applies to the view subviews only.
Therefore to animate the view constraint, it is important to call it on the view-to-animate superview as follows:
topConstraint.constant = heightShift
UIView.animate(withDuration: 0.3) {
// request layout on the *superview*
self.view.superview?.layoutIfNeeded()
}
An example for a simple layout as follows:
class MyClass {
/// Container view
let container = UIView()
/// View attached to container
let view = UIView()
/// Top constraint to animate
var topConstraint = NSLayoutConstraint()
/// Create the UI hierarchy and constraints
func createUI() {
container.addSubview(view)
// Create the top constraint
topConstraint = view.topAnchor.constraint(equalTo: container.topAnchor, constant: 0)
view.translatesAutoresizingMaskIntoConstraints = false
// Activate constaint(s)
NSLayoutConstraint.activate([
topConstraint,
])
}
/// Update view constraint with animation
func updateConstraint(heightShift: CGFloat) {
topConstraint.constant = heightShift
UIView.animate(withDuration: 0.3) {
// request layout on the *superview*
self.view.superview?.layoutIfNeeded()
}
}
}
Index (zero based) must be greater than or equal to zero
This can also happen when trying to throw an ArgumentException
where you inadvertently call the ArgumentException
constructor overload
public static void Dostuff(Foo bar)
{
// this works
throw new ArgumentException(String.Format("Could not find {0}", bar.SomeStringProperty));
//this gives the error
throw new ArgumentException(String.Format("Could not find {0}"), bar.SomeStringProperty);
}
Convert .pfx to .cer
PFX files are PKCS#12 Personal Information Exchange Syntax Standard bundles. They can include arbitrary number of private keys with accompanying X.509 certificates and a certificate authority chain (set certificates).
If you want to extract client certificates, you can use OpenSSL's PKCS12 tool.
openssl pkcs12 -in input.pfx -out mycerts.crt -nokeys -clcerts
The command above will output certificate(s) in PEM format. The ".crt" file extension is handled by both macOS and Window.
You mention ".cer" extension in the question which is conventionally used for the DER encoded files. A binary encoding. Try the ".crt" file first and if it's not accepted, easy to convert from PEM to DER:
openssl x509 -inform pem -in mycerts.crt -outform der -out mycerts.cer
What is the return value of os.system() in Python?
You might want to use
return_value = os.popen('ls').read()
instead. os.system
only returns the error value.
The os.popen
is a neater wrapper for subprocess.Popen
function as is seen within the python source code.
How do I convert ticks to minutes?
A single tick represents one hundred nanoseconds or one ten-millionth of a second. FROM MSDN.
So 28 000 000 000 * 1/10 000 000 = 2 800 sec.
2 800 sec /60 = 46.6666min
Or you can do it programmaticly with TimeSpan:
static void Main()
{
TimeSpan ts = TimeSpan.FromTicks(28000000000);
double minutesFromTs = ts.TotalMinutes;
Console.WriteLine(minutesFromTs);
Console.Read();
}
Both give me 46 min and not 480 min...
ADB device list is empty
This helped me at the end:
Quick guide:
Download Google USB Driver
Connect your device with Android Debugging enabled to your PC
Open Device Manager of Windows from System Properties.
Your device should appear under Other devices
listed as something like
Android ADB Interface
or 'Android Phone' or similar. Right-click that and
click on Update Driver Software...
Select Browse my computer for driver software
Select Let me pick from a list of device drivers on my computer
Double-click Show all devices
Press the Have disk
button
Browse and navigate to [wherever your SDK has been installed]\google-usb_driver and select android_winusb.inf
Select Android ADB Interface
from the list of device types.
Press the Yes
button
Press the Install
button
Press the Close
button
Now you've got the ADB driver set up correctly. Reconnect your device if it
doesn't recognize it already.
bash "if [ false ];" returns true instead of false -- why?
Using true/false removes some bracket clutter...
#! /bin/bash
# true_or_false.bash
[ "$(basename $0)" == "bash" ] && sourced=true || sourced=false
$sourced && echo "SOURCED"
$sourced || echo "CALLED"
# Just an alternate way:
! $sourced && echo "CALLED " || echo "SOURCED"
$sourced && return || exit
How to upload and parse a CSV file in php
untested but should give you the idea. the view:
<form action="upload.php" method="post" enctype="multipart/form-data">
<input type="file" name="csv" value="" />
<input type="submit" name="submit" value="Save" /></form>
upload.php controller:
$csv = array();
// check there are no errors
if($_FILES['csv']['error'] == 0){
$name = $_FILES['csv']['name'];
$ext = strtolower(end(explode('.', $_FILES['csv']['name'])));
$type = $_FILES['csv']['type'];
$tmpName = $_FILES['csv']['tmp_name'];
// check the file is a csv
if($ext === 'csv'){
if(($handle = fopen($tmpName, 'r')) !== FALSE) {
// necessary if a large csv file
set_time_limit(0);
$row = 0;
while(($data = fgetcsv($handle, 1000, ',')) !== FALSE) {
// number of fields in the csv
$col_count = count($data);
// get the values from the csv
$csv[$row]['col1'] = $data[0];
$csv[$row]['col2'] = $data[1];
// inc the row
$row++;
}
fclose($handle);
}
}
}
Python Create unix timestamp five minutes in the future
You can use datetime.strftime
to get the time in Epoch form, using the %s
format string:
def expires():
future = datetime.datetime.now() + datetime.timedelta(seconds=5*60)
return int(future.strftime("%s"))
Note:
This only works under linux, and this method doesn't work with timezones.
How do I vertically align text in a div?
You need to add the line-height
attribute and that attribute must match the height of the div
. In your case:
_x000D_
_x000D_
.center {_x000D_
height: 309px;_x000D_
line-height: 309px; /* same as height! */_x000D_
}
_x000D_
<div class="center">_x000D_
A single line._x000D_
</div>
_x000D_
_x000D_
_x000D_
In fact, you could probably remove the height
attribute altogether.
This only works for one line of text though, so be careful.
"Proxy server connection failed" in google chrome
- Open Google Chrome.
- Click Menu on the upper right side. Beside the STAR symbol (Bookmark).
- Click Show Advanced Settings.
- Scroll down and find Network.
- Click Change proxy settings.
- On the Connections tab, click LAN settings.
- Uncheck "Use a proxy server for your LAN."
- Then click OK.
Hope it helps .
Pointer to a string in C?
The same notation is used for pointing at a single character or the first character of a null-terminated string:
char c = 'Z';
char a[] = "Hello world";
char *ptr1 = &c;
char *ptr2 = a; // Points to the 'H' of "Hello world"
char *ptr3 = &a[0]; // Also points to the 'H' of "Hello world"
char *ptr4 = &a[6]; // Points to the 'w' of "world"
char *ptr5 = a + 6; // Also points to the 'w' of "world"
The values in ptr2
and ptr3
are the same; so are the values in ptr4
and ptr5
. If you're going to treat some data as a string, it is important to make sure it is null terminated, and that you know how much space there is for you to use. Many problems are caused by not understanding what space is available and not knowing whether the string was properly null terminated.
Note that all the pointers above can be dereferenced as if they were an array:
*ptr1 == 'Z'
ptr1[0] == 'Z'
*ptr2 == 'H'
ptr2[0] == 'H'
ptr2[4] == 'o'
*ptr4 == 'w'
ptr4[0] == 'w'
ptr4[4] == 'd'
ptr5[0] == ptr3[6]
*(ptr5+0) == *(ptr3+6)
Late addition to question
What does char (*ptr)[N];
represent?
This is a more complex beastie altogether. It is a pointer to an array of N
characters. The type is quite different; the way it is used is quite different; the size of the object pointed to is quite different.
char (*ptr)[12] = &a;
(*ptr)[0] == 'H'
(*ptr)[6] == 'w'
*(*ptr + 6) == 'w'
Note that ptr + 1
points to undefined territory, but points 'one array of 12 bytes' beyond the start of a
. Given a slightly different scenario:
char b[3][12] = { "Hello world", "Farewell", "Au revoir" };
char (*pb)[12] = &b[0];
Now:
(*(pb+0))[0] == 'H'
(*(pb+1))[0] == 'F'
(*(pb+2))[5] == 'v'
You probably won't come across pointers to arrays except by accident for quite some time; I've used them a few times in the last 25 years, but so few that I can count the occasions on the fingers of one hand (and several of those have been answering questions on Stack Overflow). Beyond knowing that they exist, that they are the result of taking the address of an array, and that you probably didn't want it, you don't really need to know more about pointers to arrays.
Converting a character code to char (VB.NET)
you can also use
Dim intValue as integer = 65 ' letter A for instance
Dim strValue As String = Char.ConvertFromUtf32(intValue)
this doesn't requirement Microsoft.VisualBasic reference
Where and why do I have to put the "template" and "typename" keywords?
(See here also for my C++11 answer)
In order to parse a C++ program, the compiler needs to know whether certain names are types or not. The following example demonstrates that:
t * f;
How should this be parsed? For many languages a compiler doesn't need to know the meaning of a name in order to parse and basically know what action a line of code does. In C++, the above however can yield vastly different interpretations depending on what t
means. If it's a type, then it will be a declaration of a pointer f
. However if it's not a type, it will be a multiplication. So the C++ Standard says at paragraph (3/7):
Some names denote types or templates. In general, whenever a name is encountered it is necessary to determine whether that name denotes one of these entities before continuing to parse the program that contains it. The process that determines this is called name lookup.
How will the compiler find out what a name t::x
refers to, if t
refers to a template type parameter? x
could be a static int data member that could be multiplied or could equally well be a nested class or typedef that could yield to a declaration. If a name has this property - that it can't be looked up until the actual template arguments are known - then it's called a dependent name (it "depends" on the template parameters).
You might recommend to just wait till the user instantiates the template:
Let's wait until the user instantiates the template, and then later find out the real meaning of t::x * f;
.
This will work and actually is allowed by the Standard as a possible implementation approach. These compilers basically copy the template's text into an internal buffer, and only when an instantiation is needed, they parse the template and possibly detect errors in the definition. But instead of bothering the template's users (poor colleagues!) with errors made by a template's author, other implementations choose to check templates early on and give errors in the definition as soon as possible, before an instantiation even takes place.
So there has to be a way to tell the compiler that certain names are types and that certain names aren't.
The "typename" keyword
The answer is: We decide how the compiler should parse this. If t::x
is a dependent name, then we need to prefix it by typename
to tell the compiler to parse it in a certain way. The Standard says at (14.6/2):
A name used in a template declaration or definition and that is dependent on a template-parameter is
assumed not to name a type unless the applicable name lookup finds a type name or the name is qualified
by the keyword typename.
There are many names for which typename
is not necessary, because the compiler can, with the applicable name lookup in the template definition, figure out how to parse a construct itself - for example with T *f;
, when T
is a type template parameter. But for t::x * f;
to be a declaration, it must be written as typename t::x *f;
. If you omit the keyword and the name is taken to be a non-type, but when instantiation finds it denotes a type, the usual error messages are emitted by the compiler. Sometimes, the error consequently is given at definition time:
// t::x is taken as non-type, but as an expression the following misses an
// operator between the two names or a semicolon separating them.
t::x f;
The syntax allows typename
only before qualified names - it is therefor taken as granted that unqualified names are always known to refer to types if they do so.
A similar gotcha exists for names that denote templates, as hinted at by the introductory text.
The "template" keyword
Remember the initial quote above and how the Standard requires special handling for templates as well? Let's take the following innocent-looking example:
boost::function< int() > f;
It might look obvious to a human reader. Not so for the compiler. Imagine the following arbitrary definition of boost::function
and f
:
namespace boost { int function = 0; }
int main() {
int f = 0;
boost::function< int() > f;
}
That's actually a valid expression! It uses the less-than operator to compare boost::function
against zero (int()
), and then uses the greater-than operator to compare the resulting bool
against f
. However as you might well know, boost::function
in real life is a template, so the compiler knows (14.2/3):
After name lookup (3.4) finds that a name is a template-name, if this name is followed by a <, the < is
always taken as the beginning of a template-argument-list and never as a name followed by the less-than
operator.
Now we are back to the same problem as with typename
. What if we can't know yet whether the name is a template when parsing the code? We will need to insert template
immediately before the template name, as specified by 14.2/4
. This looks like:
t::template f<int>(); // call a function template
Template names can not only occur after a ::
but also after a ->
or .
in a class member access. You need to insert the keyword there too:
this->template f<int>(); // call a function template
Dependencies
For the people that have thick Standardese books on their shelf and that want to know what exactly I was talking about, I'll talk a bit about how this is specified in the Standard.
In template declarations some constructs have different meanings depending on what template arguments you use to instantiate the template: Expressions may have different types or values, variables may have different types or function calls might end up calling different functions. Such constructs are generally said to depend on template parameters.
The Standard defines precisely the rules by whether a construct is dependent or not. It separates them into logically different groups: One catches types, another catches expressions. Expressions may depend by their value and/or their type. So we have, with typical examples appended:
- Dependent types (e.g: a type template parameter
T
)
- Value-dependent expressions (e.g: a non-type template parameter
N
)
- Type-dependent expressions (e.g: a cast to a type template parameter
(T)0
)
Most of the rules are intuitive and are built up recursively: For example, a type constructed as T[N]
is a dependent type if N
is a value-dependent expression or T
is a dependent type. The details of this can be read in section (14.6.2/1
) for dependent types, (14.6.2.2)
for type-dependent expressions and (14.6.2.3)
for value-dependent expressions.
Dependent names
The Standard is a bit unclear about what exactly is a dependent name. On a simple read (you know, the principle of least surprise), all it defines as a dependent name is the special case for function names below. But since clearly T::x
also needs to be looked up in the instantiation context, it also needs to be a dependent name (fortunately, as of mid C++14 the committee has started to look into how to fix this confusing definition).
To avoid this problem, I have resorted to a simple interpretation of the Standard text. Of all the constructs that denote dependent types or expressions, a subset of them represent names. Those names are therefore "dependent names". A name can take different forms - the Standard says:
A name is a use of an identifier (2.11), operator-function-id (13.5), conversion-function-id (12.3.2), or template-id (14.2) that denotes an entity or label (6.6.4, 6.1)
An identifier is just a plain sequence of characters / digits, while the next two are the operator +
and operator type
form. The last form is template-name <argument list>
. All these are names, and by conventional use in the Standard, a name can also include qualifiers that say what namespace or class a name should be looked up in.
A value dependent expression 1 + N
is not a name, but N
is. The subset of all dependent constructs that are names is called dependent name. Function names, however, may have different meaning in different instantiations of a template, but unfortunately are not caught by this general rule.
Dependent function names
Not primarily a concern of this article, but still worth mentioning: Function names are an exception that are handled separately. An identifier function name is dependent not by itself, but by the type dependent argument expressions used in a call. In the example f((T)0)
, f
is a dependent name. In the Standard, this is specified at (14.6.2/1)
.
Additional notes and examples
In enough cases we need both of typename
and template
. Your code should look like the following
template <typename T, typename Tail>
struct UnionNode : public Tail {
// ...
template<typename U> struct inUnion {
typedef typename Tail::template inUnion<U> dummy;
};
// ...
};
The keyword template
doesn't always have to appear in the last part of a name. It can appear in the middle before a class name that's used as a scope, like in the following example
typename t::template iterator<int>::value_type v;
In some cases, the keywords are forbidden, as detailed below
On the name of a dependent base class you are not allowed to write typename
. It's assumed that the name given is a class type name. This is true for both names in the base-class list and the constructor initializer list:
template <typename T>
struct derive_from_Has_type : /* typename */ SomeBase<T>::type
{ };
In using-declarations it's not possible to use template
after the last ::
, and the C++ committee said not to work on a solution.
template <typename T>
struct derive_from_Has_type : SomeBase<T> {
using SomeBase<T>::template type; // error
using typename SomeBase<T>::type; // typename *is* allowed
};
Can I find events bound on an element with jQuery?
I'm adding this for posterity; There's an easier way that doesn't involve writing more JS. Using the amazing firebug addon for firefox,
- Right click on the element and select 'Inspect element with Firebug'
- In the sidebar panels (shown in the screenshot), navigate to the events tab using the tiny > arrow
- The events tab shows the events and corresponding functions for each event
- The text next to it shows the function location