mysqli or PDO - what are the pros and cons?
Well, you could argue with the object oriented aspect, the prepared statements, the fact that it becomes a standard, etc. But I know that most of the time, convincing somebody works better with a killer feature. So there it is:
A really nice thing with PDO is you can fetch the data, injecting it automatically in an object. If you don't want to use an ORM (cause it's a just a quick script) but you do like object mapping, it's REALLY cool :
class Student {
public $id;
public $first_name;
public $last_name
public function getFullName() {
return $this->first_name.' '.$this->last_name
}
}
try
{
$dbh = new PDO("mysql:host=$hostname;dbname=school", $username, $password)
$stmt = $dbh->query("SELECT * FROM students");
/* MAGIC HAPPENS HERE */
$stmt->setFetchMode(PDO::FETCH_INTO, new Student);
foreach($stmt as $student)
{
echo $student->getFullName().'<br />';
}
$dbh = null;
}
catch(PDOException $e)
{
echo $e->getMessage();
}
font-weight is not working properly?
Most browsers don't fully support the numerical values for font-weight
. Here's a good article about the problem, and even tough it's a little old, it does seem to be correct.
If you need something bolder then you might want to try using a different font that's bolder than your existing one. Naturally, you could probably adjust the font size for a similar effect.
Change language of Visual Studio 2017 RC
For having a language at Visual Studio Ui , basically the language package of that language must be installed during the installation.
You can not select a language in options -> environment ->
international settings that didn't installed.
If the language that you want to select in above path is not appearing than you have to modify your visual studio by re-executing installer and selecting Language Packages tab and check your language that you want to have.
And than at Visual Studio toolbar just click Tools --> Options -->
Environment --> International Settings and than select your language
from dropdown list.
$this->session->set_flashdata() and then $this->session->flashdata() doesn't work in codeigniter
Displaying a flash message after redirect in Codeigniter
In Your Controller set this
<?php
public function change_password(){
if($this->input->post('submit')){
$change = $this->common_register->change_password();
if($change == true){
$messge = array('message' => 'Password chnage successfully','class' => 'alert alert-success fade in');
$this->session->set_flashdata('item', $messge);
}else{
$messge = array('message' => 'Wrong password enter','class' => 'alert alert-danger fade in');
$this->session->set_flashdata('item',$messge );
}
$this->session->keep_flashdata('item',$messge);
redirect('controllername/methodname','refresh');
}
?>
In Your View File Set this
<script type="application/javascript">
/** After windod Load */
$(window).bind("load", function() {
window.setTimeout(function() {
$(".alert").fadeTo(500, 0).slideUp(500, function(){
$(this).remove();
});
}, 4000);
});
</script>
<?php
if($this->session->flashdata('item')) {
$message = $this->session->flashdata('item');
?>
<div class="<?php echo $message['class'] ?>"><?php echo $message['message']; ?>
</div>
<?php
}
?>
Please check below link for Displaying a flash message after redirect in Codeigniter
What is the difference between statically typed and dynamically typed languages?
Statically typed languages
A language is statically typed if the type of a variable is known at compile time. For some languages this means that you as the programmer must specify what type each variable is (e.g.: Java, C, C++); other languages offer some form of type inference, the capability of the type system to deduce the type of a variable (e.g.: OCaml, Haskell, Scala, Kotlin)
The main advantage here is that all kinds of checking can be done by the compiler, and therefore a lot of trivial bugs are caught at a very early stage.
Examples: C, C++, Java, Rust, Go, Scala
Dynamically typed languages
A language is dynamically typed if the type is associated with run-time values, and not named variables/fields/etc. This means that you as a programmer can write a little quicker because you do not have to specify types every time (unless using a statically-typed language with type inference).
Examples: Perl, Ruby, Python, PHP, JavaScript
Most scripting languages have this feature as there is no compiler to do static type-checking anyway, but you may find yourself searching for a bug that is due to the interpreter misinterpreting the type of a variable. Luckily, scripts tend to be small so bugs have not so many places to hide.
Most dynamically typed languages do allow you to provide type information, but do not require it. One language that is currently being developed, Rascal, takes a hybrid approach allowing dynamic typing within functions but enforcing static typing for the function signature.
PHP and MySQL Select a Single Value
You do this by using mysqli_fetch_field
method.
session_start();
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
$name = $_GET["username"];
$sql = "SELECT 'id' FROM Users WHERE username='$name' limit 1";
$result = mysqli_query($link, $sql);
if ($result !== false) {
$value = mysqli_fetch_field($result);
$_SESSION['myid'] = $value;
}
Note: you can do that by using mysql_fetch_field()
method as well, but it will be deprecated in php v5.5
How to get root view controller?
if you are trying to access the rootViewController
you set in your appDelegate. try this:
Objective-C
YourViewController *rootController = (YourViewController*)[[(YourAppDelegate*)
[[UIApplication sharedApplication]delegate] window] rootViewController];
Swift
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let viewController = appDelegate.window!.rootViewController as YourViewController
Swift 3
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let viewController = appDelegate.window!.rootViewController as! YourViewController
Swift 4 & 4.2
let viewController = UIApplication.shared.keyWindow!.rootViewController as! YourViewController
Swift 5 & 5.1 & 5.2
let viewController = UIApplication.shared.windows.first!.rootViewController as! YourViewController
How do I see which checkbox is checked?
you can check that by either isset()
or empty()
(its check explicit isset) weather check box is checked or not
for example
<input type='checkbox' name='Mary' value='2' id='checkbox' />
here you can check by
if (isset($_POST['Mary'])) {
echo "checked!";
}
or
if (!empty($_POST['Mary'])) {
echo "checked!";
}
the above will check only one if you want to do for many than you can make an array instead writing separate for all checkbox try like
<input type="checkbox" name="formDoor[]" value="A" />Acorn Building<br />
<input type="checkbox" name="formDoor[]" value="B" />Brown Hall<br />
<input type="checkbox" name="formDoor[]" value="C" />Carnegie Complex<br />
php
$aDoor = $_POST['formDoor'];
if(empty($aDoor))
{
echo("You didn't select any buildings.");
}
else
{
$N = count($aDoor);
echo("You selected $N door(s): ");
for($i=0; $i < $N; $i++)
{
echo htmlspecialchars($aDoor[$i] ). " ";
}
}
grep's at sign caught as whitespace
After some time with Google I asked on the ask ubuntu chat room.
A user there was king enough to help me find the solution I was looking for and i wanted to share so that any following suers running into this may find it:
grep -P "(^|\s)abc(\s|$)"
gives the result I was looking for. -P is an experimental implementation of perl regexps.
grepping for abc
and then using filters like grep -v '@abc'
(this is far from perfect...) should also work, but my patch does something similar.
javaw.exe cannot find path
Make sure to download these from here:
Also create PATH
enviroment variable on you computer like this (if it doesn't exist already):
- Right click on My Computer/Computer
- Properties
- Advanced system settings (or just Advanced)
- Enviroment variables
- If
PATH
variable doesn't exist among "User variables" click New
(Variable name: PATH, Variable value : C:\Program Files\Java\jdk1.8.0\bin;
<-- please check out the right version, this may differ as Oracle keeps updating Java). ;
in the end enables assignment of multiple values to PATH
variable.
- Click OK! Done
To be sure that everything works, open CMD Prompt and type: java -version
to check for Java version and javac
to be sure that compiler responds.
I hope this helps. Good luck!
How to find sitemap.xml path on websites?
According to protocol documentation there are at least three options website designers can use to inform sitemap.xml location to search engines:
- Informing each search engine of the location through their provided interface
- Adding url to the robots.txt file
- Submiting url to search engines through http
So, unless they have chosen to publish the sitemap location on their robots.txt file, you cannot really know where they have put their sitemap.xml files.
How to create our own Listener interface in android?
There are 4 steps:
1.create interface class (listener)
2.use interface in view 1 (define variable)
3.implements interface to view 2 (view 1 used in view 2)
4.pass interface in view 1 to view 2
Example:
Step 1: you need create interface and definde function
public interface onAddTextViewCustomListener {
void onAddText(String text);
}
Step 2: use this interface in view
public class CTextView extends TextView {
onAddTextViewCustomListener onAddTextViewCustomListener; //listener custom
public CTextView(Context context, onAddTextViewCustomListener onAddTextViewCustomListener) {
super(context);
this.onAddTextViewCustomListener = onAddTextViewCustomListener;
init(context, null);
}
public CTextView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
public CTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context, attrs);
}
@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
public CTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init(context, attrs);
}
public void init(Context context, @Nullable AttributeSet attrs) {
if (isInEditMode())
return;
//call listener
onAddTextViewCustomListener.onAddText("this TextView added");
}
}
Step 3,4: implements to activity
public class MainActivity extends AppCompatActivity implements onAddTextViewCustomListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//get main view from layout
RelativeLayout mainView = (RelativeLayout)findViewById(R.id.mainView);
//create new CTextView and set listener
CTextView cTextView = new CTextView(getApplicationContext(), this);
//add cTextView to mainView
mainView.addView(cTextView);
}
@Override
public void onAddText(String text) {
Log.i("Message ", text);
}
}
How to delete an SMS from the inbox in Android programmatically?
"As of Android 1.6, incoming SMS message broadcasts (android.provider.Telephony.SMS_RECEIVED
) are delivered as an "ordered broadcast" — meaning that you can tell the system which components should receive the broadcast first."
This means that you can intercept incoming message and abort broadcasting of it further on.
In your AndroidManifest.xml
file, make sure to have priority set to highest:
<receiver android:name=".receiver.SMSReceiver" android:enabled="true">
<intent-filter android:priority="1000">
<action android:name="android.provider.Telephony.SMS_RECEIVED" />
</intent-filter>
</receiver>
In your BroadcastReceiver
, in onReceive()
method, before performing anything with your message, simply call abortBroadcast();
EDIT: As of KitKat, this doesn't work anymore apparently.
EDIT2: More info on how to do it on KitKat here:
Delete SMS from android on 4.4.4 (Affected rows = 0(Zero), after deleted)
SQL WHERE.. IN clause multiple columns
Why use WHERE EXISTS or DERIVED TABLES when you can just do a normal inner join:
SELECT t.*
FROM table1 t
INNER JOIN CRM_VCM_CURRENT_LEAD_STATUS s
ON t.CM_PLAN_ID = s.CM_PLAN_ID
AND t.Individual_ID = s.Individual_ID
WHERE s.Lead_Key = :_Lead_Key
If the pair of (CM_PLAN_ID, Individual_ID) isn't unique in the status table, you might need a SELECT DISTINCT t.* instead.
How to set an image as a background for Frame in Swing GUI of java?
Here is another quick approach without using additional panel.
JFrame f = new JFrame("stackoverflow") {
private Image backgroundImage = ImageIO.read(new File("background.jpg"));
public void paint( Graphics g ) {
super.paint(g);
g.drawImage(backgroundImage, 0, 0, null);
}
};
Using StringWriter for XML Serialization
<TL;DR> The problem is rather simple, actually: you are not matching the declared encoding (in the XML declaration) with the datatype of the input parameter. If you manually added <?xml version="1.0" encoding="utf-8"?><test/>
to the string, then declaring the SqlParameter
to be of type SqlDbType.Xml
or SqlDbType.NVarChar
would give you the "unable to switch the encoding" error. Then, when inserting manually via T-SQL, since you switched the declared encoding to be utf-16
, you were clearly inserting a VARCHAR
string (not prefixed with an upper-case "N", hence an 8-bit encoding, such as UTF-8) and not an NVARCHAR
string (prefixed with an upper-case "N", hence the 16-bit UTF-16 LE encoding).
The fix should have been as simple as:
- In the first case, when adding the declaration stating
encoding="utf-8"
: simply don't add the XML declaration.
- In the second case, when adding the declaration stating
encoding="utf-16"
: either
- simply don't add the XML declaration, OR
- simply add an "N" to the input parameter type:
SqlDbType.NVarChar
instead of SqlDbType.VarChar
:-) (or possibly even switch to using SqlDbType.Xml
)
(Detailed response is below)
All of the answers here are over-complicated and unnecessary (regardless of the 121 and 184 up-votes for Christian's and Jon's answers, respectively). They might provide working code, but none of them actually answer the question. The issue is that nobody truly understood the question, which ultimately is about how the XML datatype in SQL Server works. Nothing against those two clearly intelligent people, but this question has little to nothing to do with serializing to XML. Saving XML data into SQL Server is much easier than what is being implied here.
It doesn't really matter how the XML is produced as long as you follow the rules of how to create XML data in SQL Server. I have a more thorough explanation (including working example code to illustrate the points outlined below) in an answer on this question: How to solve “unable to switch the encoding” error when inserting XML into SQL Server, but the basics are:
- The XML declaration is optional
- The XML datatype stores strings always as UCS-2 / UTF-16 LE
- If your XML is UCS-2 / UTF-16 LE, then you:
- pass in the data as either
NVARCHAR(MAX)
or XML
/ SqlDbType.NVarChar
(maxsize = -1) or SqlDbType.Xml
, or if using a string literal then it must be prefixed with an upper-case "N".
- if specifying the XML declaration, it must be either "UCS-2" or "UTF-16" (no real difference here)
- If your XML is 8-bit encoded (e.g. "UTF-8" / "iso-8859-1" / "Windows-1252"), then you:
- need to specify the XML declaration IF the encoding is different than the code page specified by the default Collation of the database
- you must pass in the data as
VARCHAR(MAX)
/ SqlDbType.VarChar
(maxsize = -1), or if using a string literal then it must not be prefixed with an upper-case "N".
- Whatever 8-bit encoding is used, the "encoding" noted in the XML declaration must match the actual encoding of the bytes.
- The 8-bit encoding will be converted into UTF-16 LE by the XML datatype
With the points outlined above in mind, and given that strings in .NET are always UTF-16 LE / UCS-2 LE (there is no difference between those in terms of encoding), we can answer your questions:
Is there a reason why I shouldn't use StringWriter to serialize an Object when I need it as a string afterwards?
No, your StringWriter
code appears to be just fine (at least I see no issues in my limited testing using the 2nd code block from the question).
Wouldn't setting the encoding to UTF-16 (in the xml tag) work then?
It isn't necessary to provide the XML declaration. When it is missing, the encoding is assumed to be UTF-16 LE if you pass the string into SQL Server as NVARCHAR
(i.e. SqlDbType.NVarChar
) or XML
(i.e. SqlDbType.Xml
). The encoding is assumed to be the default 8-bit Code Page if passing in as VARCHAR
(i.e. SqlDbType.VarChar
). If you have any non-standard-ASCII characters (i.e. values 128 and above) and are passing in as VARCHAR
, then you will likely see "?" for BMP characters and "??" for Supplementary Characters as SQL Server will convert the UTF-16 string from .NET into an 8-bit string of the current Database's Code Page before converting it back into UTF-16 / UCS-2. But you shouldn't get any errors.
On the other hand, if you do specify the XML declaration, then you must pass into SQL Server using the matching 8-bit or 16-bit datatype. So if you have a declaration stating that the encoding is either UCS-2 or UTF-16, then you must pass in as SqlDbType.NVarChar
or SqlDbType.Xml
. Or, if you have a declaration stating that the encoding is one of the 8-bit options (i.e. UTF-8
, Windows-1252
, iso-8859-1
, etc), then you must pass in as SqlDbType.VarChar
. Failure to match the declared encoding with the proper 8 or 16 -bit SQL Server datatype will result in the "unable to switch the encoding" error that you were getting.
For example, using your StringWriter
-based serialization code, I simply printed the resulting string of the XML and used it in SSMS. As you can see below, the XML declaration is included (because StringWriter
does not have an option to OmitXmlDeclaration
like XmlWriter
does), which poses no problem so long as you pass the string in as the correct SQL Server datatype:
-- Upper-case "N" prefix == NVARCHAR, hence no error:
DECLARE @Xml XML = N'<?xml version="1.0" encoding="utf-16"?>
<string>Test ?</string>';
SELECT @Xml;
-- <string>Test ?</string>
As you can see, it even handles characters beyond standard ASCII, given that ?
is BMP Code Point U+1234, and
is Supplementary Character Code Point U+1F638. However, the following:
-- No upper-case "N" prefix on the string literal, hence VARCHAR:
DECLARE @Xml XML = '<?xml version="1.0" encoding="utf-16"?>
<string>Test ?</string>';
results in the following error:
Msg 9402, Level 16, State 1, Line XXXXX
XML parsing: line 1, character 39, unable to switch the encoding
Ergo, all of that explanation aside, the full solution to your original question is:
You were clearly passing the string in as SqlDbType.VarChar
. Switch to SqlDbType.NVarChar
and it will work without needing to go through the extra step of removing the XML declaration. This is preferred over keeping SqlDbType.VarChar
and removing the XML declaration because this solution will prevent data loss when the XML includes non-standard-ASCII characters. For example:
-- No upper-case "N" prefix on the string literal == VARCHAR, and no XML declaration:
DECLARE @Xml2 XML = '<string>Test ?</string>';
SELECT @Xml2;
-- <string>Test ???</string>
As you can see, there is no error this time, but now there is data-loss 🙀.
DELETE ... FROM ... WHERE ... IN
The canonical T-SQL (SqlServer) answer is to use a DELETE
with JOIN
as such
DELETE o
FROM Orders o
INNER JOIN Customers c
ON o.CustomerId = c.CustomerId
WHERE c.FirstName = 'sklivvz'
This will delete all orders which have a customer with first name Sklivvz.
How to customize the background color of a UITableViewCell?
My solution is to add the following code to the cellForRowAtIndexPath event:
UIView *solidColor = [cell viewWithTag:100];
if (!solidColor) {
solidColor = [[UIView alloc] initWithFrame:cell.bounds];
solidColor.tag = 100; //Big tag to access the view afterwards
[cell addSubview:solidColor];
[cell sendSubviewToBack:solidColor];
[solidColor release];
}
solidColor.backgroundColor = [UIColor colorWithRed:254.0/255.0
green:233.0/255.0
blue:233.0/255.0
alpha:1.0];
Works under any circumstances, even with disclosure buttons, and is better for your logic to act on cells color state in cellForRowAtIndexPath than in cellWillShow event I think.
How do I suspend painting for a control and its children?
A nice solution without using interop:
As always, simply enable DoubleBuffered=true on your CustomControl. Then, if you have any containers like FlowLayoutPanel or TableLayoutPanel, derive a class from each of these types and in the constructors, enable double buffering. Now, simply use your derived Containers instead of the Windows.Forms Containers.
class TableLayoutPanel : System.Windows.Forms.TableLayoutPanel
{
public TableLayoutPanel()
{
DoubleBuffered = true;
}
}
class FlowLayoutPanel : System.Windows.Forms.FlowLayoutPanel
{
public FlowLayoutPanel()
{
DoubleBuffered = true;
}
}
LINQ: Select an object and change some properties without creating a new object
There shouldn't be any LINQ magic keeping you from doing this. Don't use projection though that'll return an anonymous type.
User u = UserCollection.FirstOrDefault(u => u.Id == 1);
u.FirstName = "Bob"
That will modify the real object, as well as:
foreach (User u in UserCollection.Where(u => u.Id > 10)
{
u.Property = SomeValue;
}
Automatic creation date for Django model form objects?
Well, the above answer is correct, auto_now_add and auto_now would do it, but it would be better to make an abstract class and use it in any model where you require created_at
and updated_at
fields.
class TimeStampMixin(models.Model):
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
class Meta:
abstract = True
Now anywhere you want to use it you can do a simple inherit and you can use timestamp in any model you make like.
class Posts(TimeStampMixin):
name = models.CharField(max_length=50)
...
...
In this way, you can leverage object-oriented reusability, in Django DRY(don't repeat yourself)
How do I force files to open in the browser instead of downloading (PDF)?
To indicate to the browser that the file should be viewed in the browser, the HTTP response should include these headers:
Content-Type: application/pdf
Content-Disposition: inline; filename="filename.pdf"
To have the file downloaded rather than viewed:
Content-Type: application/pdf
Content-Disposition: attachment; filename="filename.pdf"
The quotes around the filename are required if the filename contains special characters such as filename[1].pdf
which may otherwise break the browser's ability to handle the response.
How you set the HTTP response headers will depend on your HTTP server (or, if you are generating the PDF response from server-side code: your server-side programming language).
Transfer git repositories from GitLab to GitHub - can we, how to and pitfalls (if any)?
This is very easy by import repository feature
Login to github.com
,
Side of profile picture you will find +
button click on that then there will be option to import repository
.
you will find page like this.
Your old repository’s clone URL is required which is gitlab repo url in your case.
then select Owner and then type name for this repo and click to begin import button.
How to create a trie in Python
Python Class for Trie
Trie Data Structure can be used to store data in O(L)
where L is the length of the string so for inserting N strings time complexity would be O(NL)
the string can be searched in O(L)
only same goes for deletion.
Can be clone from https://github.com/Parikshit22/pytrie.git
class Node:
def __init__(self):
self.children = [None]*26
self.isend = False
class trie:
def __init__(self,):
self.__root = Node()
def __len__(self,):
return len(self.search_byprefix(''))
def __str__(self):
ll = self.search_byprefix('')
string = ''
for i in ll:
string+=i
string+='\n'
return string
def chartoint(self,character):
return ord(character)-ord('a')
def remove(self,string):
ptr = self.__root
length = len(string)
for idx in range(length):
i = self.chartoint(string[idx])
if ptr.children[i] is not None:
ptr = ptr.children[i]
else:
raise ValueError("Keyword doesn't exist in trie")
if ptr.isend is not True:
raise ValueError("Keyword doesn't exist in trie")
ptr.isend = False
return
def insert(self,string):
ptr = self.__root
length = len(string)
for idx in range(length):
i = self.chartoint(string[idx])
if ptr.children[i] is not None:
ptr = ptr.children[i]
else:
ptr.children[i] = Node()
ptr = ptr.children[i]
ptr.isend = True
def search(self,string):
ptr = self.__root
length = len(string)
for idx in range(length):
i = self.chartoint(string[idx])
if ptr.children[i] is not None:
ptr = ptr.children[i]
else:
return False
if ptr.isend is not True:
return False
return True
def __getall(self,ptr,key,key_list):
if ptr is None:
key_list.append(key)
return
if ptr.isend==True:
key_list.append(key)
for i in range(26):
if ptr.children[i] is not None:
self.__getall(ptr.children[i],key+chr(ord('a')+i),key_list)
def search_byprefix(self,key):
ptr = self.__root
key_list = []
length = len(key)
for idx in range(length):
i = self.chartoint(key[idx])
if ptr.children[i] is not None:
ptr = ptr.children[i]
else:
return None
self.__getall(ptr,key,key_list)
return key_list
t = trie()
t.insert("shubham")
t.insert("shubhi")
t.insert("minhaj")
t.insert("parikshit")
t.insert("pari")
t.insert("shubh")
t.insert("minakshi")
print(t.search("minhaj"))
print(t.search("shubhk"))
print(t.search_byprefix('m'))
print(len(t))
print(t.remove("minhaj"))
print(t)
Code Oputpt
True
False
['minakshi', 'minhaj']
7
minakshi
minhajsir
pari
parikshit
shubh
shubham
shubhi
`col-xs-*` not working in Bootstrap 4
you could do this, if you want to use the old syntax (or don't want to rewrite every template)
@for $i from 1 through $grid-columns {
@include media-breakpoint-up(xs) {
.col-xs-#{$i} {
@include make-col-ready();
@include make-col($i);
}
}
}
What is the Java ?: operator called and what does it do?
I happen to really like this operator, but the reader should be taken into consideration.
You always have to balance code compactness with the time spent reading it, and in that it has some pretty severe flaws.
First of all, there is the Original Asker's case. He just spent an hour posting about it and reading the responses. How longer would it have taken the author to write every ?: as an if/then throughout the course of his entire life. Not an hour to be sure.
Secondly, in C-like languages, you get in the habit of simply knowing that conditionals are the first thing in the line. I noticed this when I was using Ruby and came across lines like:
callMethodWhatever(Long + Expression + with + syntax) if conditional
If I was a long time Ruby user I probably wouldn't have had a problem with this line, but coming from C, when you see "callMethodWhatever" as the first thing in the line, you expect it to be executed. The ?: is less cryptic, but still unusual enough as to throw a reader off.
The advantage, however, is a really cool feeling in your tummy when you can write a 3-line if statement in the space of 1 of the lines. Can't deny that :) But honestly, not necessarily more readable by 90% of the people out there simply because of its' rarity.
When it is truly an assignment based on a Boolean and values I don't have a problem with it, but it can easily be abused.
Delete file from internal storage
The getFilesDir()
somehow didn't work.
Using a method, which returns the entire path and filename gave the desired result. Here is the code:
File file = new File(inputHandle.getImgPath(id));
boolean deleted = file.delete();
Cross-Domain Cookies
Yes, it is absolutely possible to get the cookie from domain1.com by domain2.com. I had the same problem for a social plugin of my social network, and after a day of research I found the solution.
First, on the server side you need to have the following headers:
header("Access-Control-Allow-Origin: http://origin.domain:port");
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Allow-Methods: GET, POST");
header("Access-Control-Allow-Headers: Content-Type, *");
Within the PHP-file you can use $_COOKIE[name]
Second, on the client side:
Within your ajax request you need to include 2 parameters
crossDomain: true
xhrFields: { withCredentials: true }
Example:
type: "get",
url: link,
crossDomain: true,
dataType: 'json',
xhrFields: {
withCredentials: true
}
What is the fastest way to create a checksum for large files in C#
Don't checksum the entire file, create checksums every 100mb or so, so each file has a collection of checksums.
Then when comparing checksums, you can stop comparing after the first different checksum, getting out early, and saving you from processing the entire file.
It'll still take the full time for identical files.
Flutter - Wrap text on overflow, like insert ellipsis or fade
There is a very simple class TextOneLine from package assorted_layout_widgets.
Just put your text in that class.
For example:
Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
SvgPicture.asset(
loadAsset(SVG_CALL_GREEN),
width: 23,
height: 23,
fit: BoxFit.fill,
),
SizedBox(width: 16),
Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
TextOneLine(
widget.firstText,
style: findTextStyle(widget.firstTextStyle),
textAlign: TextAlign.left,
),
SizedBox(height: 4),
TextOneLine(
widget.secondText,
style: findTextStyle(widget.secondTextStyle),
textAlign: TextAlign.left,
),
],
),
),
Icon(
Icons.arrow_forward_ios,
color: Styles.iOSArrowRight,
)
],
)
Array as session variable
session_start(); //php part
$_SESSION['student']=array();
$student_name=$_POST['student_name']; //student_name form field name
$student_city=$_POST['city_id']; //city_id form field name
array_push($_SESSION['student'],$student_name,$student_city);
//print_r($_SESSION['student']);
<table class="table"> //html part
<tr>
<th>Name</th>
<th>City</th>
</tr>
<tr>
<?php for($i = 0 ; $i < count($_SESSION['student']) ; $i++) {
echo '<td>'.$_SESSION['student'][$i].'</td>';
} ?>
</tr>
</table>
Hibernate Union alternatives
I too have been through this pain - if the query is dynamically generated (e.g. Hibernate Criteria) then I couldn't find a practical way to do it.
The good news for me was that I was only investigating union to solve a performance problem when using an 'or' in an Oracle database.
The solution Patrick posted (combining the results programmatically using a set) while ugly (especially since I wanted to do results paging as well) was adequate for me.
What are the pros and cons of parquet format compared to other formats?
I think the main difference I can describe relates to record oriented vs. column oriented formats. Record oriented formats are what we're all used to -- text files, delimited formats like CSV, TSV. AVRO is slightly cooler than those because it can change schema over time, e.g. adding or removing columns from a record. Other tricks of various formats (especially including compression) involve whether a format can be split -- that is, can you read a block of records from anywhere in the dataset and still know it's schema? But here's more detail on columnar formats like Parquet.
Parquet, and other columnar formats handle a common Hadoop situation very efficiently. It is common to have tables (datasets) having many more columns than you would expect in a well-designed relational database -- a hundred or two hundred columns is not unusual. This is so because we often use Hadoop as a place to denormalize data from relational formats -- yes, you get lots of repeated values and many tables all flattened into a single one. But it becomes much easier to query since all the joins are worked out. There are other advantages such as retaining state-in-time data. So anyway it's common to have a boatload of columns in a table.
Let's say there are 132 columns, and some of them are really long text fields, each different column one following the other and use up maybe 10K per record.
While querying these tables is easy with SQL standpoint, it's common that you'll want to get some range of records based on only a few of those hundred-plus columns. For example, you might want all of the records in February and March for customers with sales > $500.
To do this in a row format the query would need to scan every record of the dataset. Read the first row, parse the record into fields (columns) and get the date and sales columns, include it in your result if it satisfies the condition. Repeat. If you have 10 years (120 months) of history, you're reading every single record just to find 2 of those months. Of course this is a great opportunity to use a partition on year and month, but even so, you're reading and parsing 10K of each record/row for those two months just to find whether the customer's sales are > $500.
In a columnar format, each column (field) of a record is stored with others of its kind, spread all over many different blocks on the disk -- columns for year together, columns for month together, columns for customer employee handbook (or other long text), and all the others that make those records so huge all in their own separate place on the disk, and of course columns for sales together. Well heck, date and months are numbers, and so are sales -- they are just a few bytes. Wouldn't it be great if we only had to read a few bytes for each record to determine which records matched our query? Columnar storage to the rescue!
Even without partitions, scanning the small fields needed to satisfy our query is super-fast -- they are all in order by record, and all the same size, so the disk seeks over much less data checking for included records. No need to read through that employee handbook and other long text fields -- just ignore them. So, by grouping columns with each other, instead of rows, you can almost always scan less data. Win!
But wait, it gets better. If your query only needed to know those values and a few more (let's say 10 of the 132 columns) and didn't care about that employee handbook column, once it had picked the right records to return, it would now only have to go back to the 10 columns it needed to render the results, ignoring the other 122 of the 132 in our dataset. Again, we skip a lot of reading.
(Note: for this reason, columnar formats are a lousy choice when doing straight transformations, for example, if you're joining all of two tables into one big(ger) result set that you're saving as a new table, the sources are going to get scanned completely anyway, so there's not a lot of benefit in read performance, and because columnar formats need to remember more about the where stuff is, they use more memory than a similar row format).
One more benefit of columnar: data is spread around. To get a single record, you can have 132 workers each read (and write) data from/to 132 different places on 132 blocks of data. Yay for parallelization!
And now for the clincher: compression algorithms work much better when it can find repeating patterns. You could compress AABBBBBBCCCCCCCCCCCCCCCC
as 2A6B16C
but ABCABCBCBCBCCCCCCCCCCCCCC
wouldn't get as small (well, actually, in this case it would, but trust me :-) ). So once again, less reading. And writing too.
So we read a lot less data to answer common queries, it's potentially faster to read and write in parallel, and compression tends to work much better.
Columnar is great when your input side is large, and your output is a filtered subset: from big to little is great. Not as beneficial when the input and outputs are about the same.
But in our case, Impala took our old Hive queries that ran in 5, 10, 20 or 30 minutes, and finished most in a few seconds or a minute.
Hope this helps answer at least part of your question!
Accessing MP3 metadata with Python
A simple example from the book Dive Into Python works ok for me, this is the download link, the example is fileinfo.py. Don't know if it's the best, but it can do the basic job.
The entire book is available online here.
Javascript call() & apply() vs bind()?
The main concept behind all this methods is Function burrowing.
Function borrowing allows us to use the methods of one object on a different object without having to make a copy of that method and maintain it in two separate places. It is accomplished through the use of . call() , . apply() , or . bind() , all of which exist to explicitly set this on the method we are borrowing
- Call invokes the function immediately and allows you to pass in arguments one by
one
- Apply invokes the function immediately and allows you to pass in arguments
as an array.
- Bind returns a new function, and you can invoke/call it anytime you want by invoking a function.
Below is an example of all this methods
let name = {
firstname : "Arham",
lastname : "Chowdhury",
}
printFullName = function(hometown,company){
console.log(this.firstname + " " + this.lastname +", " + hometown + ", " + company)
}
CALL
the first argument e.g name inside call method is always a reference
to (this) variable and latter will be function variable
printFullName.call(name,"Mumbai","Taufa"); //Arham Chowdhury, Mumbai, Taufa
APPLY
apply method is same as the call method
the only diff is that, the function arguments are passed in Array list
printFullName.apply(name, ["Mumbai","Taufa"]); //Arham Chowdhury, Mumbai, Taufa
BIND
bind method is same as call except that ,the bind returns a function that can be used later by invoking it (does'nt call it immediately)
let printMyNAme = printFullName.bind(name,"Mumbai","Taufa");
printMyNAme(); //Arham Chowdhury, Mumbai, Taufa
printMyNAme() is the function which invokes the function
below is the link for jsfiddle
https://codepen.io/Arham11/pen/vYNqExp
Can I draw rectangle in XML?
Yes you can and here is one I made earlier:
<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/listview_background_shape">
<stroke android:width="2dp" android:color="#ff207d94" />
<padding android:left="2dp"
android:top="2dp"
android:right="2dp"
android:bottom="2dp" />
<corners android:radius="5dp" />
<solid android:color="#ffffffff" />
</shape>
You can create a new XML file inside the drawable folder, and add the above code, then save it as rectangle.xml.
To use it inside a layout you would set the android:background
attribute to the new drawable shape. The shape we have defined does not have any dimensions, and therefore will take the dimensions of the View that is defined in the layout.
So putting it all together:
<View
android:id="@+id/myRectangleView"
android:layout_width="200dp"
android:layout_height="50dp"
android:background="@drawable/rectangle"/>
Finally; you can set this rectangle to be the background of any View, although for ImageViews you would use android:src
. This means you could use the rectangle as the background for ListViews, TextViews...etc.
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 $curl_errno <br/>";
}
How to make Java Set?
Like this:
import java.util.*;
Set<Integer> a = new HashSet<Integer>();
a.add( 1);
a.add( 2);
a.add( 3);
Or adding from an Array/ or multiple literals; wrap to a list, first.
Integer[] array = new Integer[]{ 1, 4, 5};
Set<Integer> b = new HashSet<Integer>();
b.addAll( Arrays.asList( b)); // from an array variable
b.addAll( Arrays.asList( 8, 9, 10)); // from literals
To get the intersection:
// copies all from A; then removes those not in B.
Set<Integer> r = new HashSet( a);
r.retainAll( b);
// and print; r.toString() implied.
System.out.println("A intersect B="+r);
Hope this answer helps. Vote for it!
Git push existing repo to a new and different remote repo server?
- Create a new repo at github.
- Clone the repo from fedorahosted to your local machine.
git remote rename origin upstream
git remote add origin URL_TO_GITHUB_REPO
git push origin master
Now you can work with it just like any other github repo. To pull in patches from upstream, simply run git pull upstream master && git push origin master
.
React.js create loop through Array
As @Alexander solves, the issue is one of async data load - you're rendering immediately and you will not have participants loaded until the async ajax call resolves and populates data
with participants
.
The alternative to the solution they provided would be to prevent render until participants exist, something like this:
render: function() {
if (!this.props.data.participants) {
return null;
}
return (
<ul className="PlayerList">
// I'm the Player List {this.props.data}
// <Player author="The Mini John" />
{
this.props.data.participants.map(function(player) {
return <li key={player}>{player}</li>
})
}
</ul>
);
}
how to query child objects in mongodb
Assuming your "states" collection is like:
{"name" : "Spain", "cities" : [ { "name" : "Madrid" }, { "name" : null } ] }
{"name" : "France" }
The query to find states with null cities would be:
db.states.find({"cities.name" : {"$eq" : null, "$exists" : true}});
It is a common mistake to query for nulls as:
db.states.find({"cities.name" : null});
because this query will return all documents lacking the key (in our example it will return Spain and France). So, unless you are sure the key is always present you must check that the key exists as in the first query.
How to open URL in Microsoft Edge from the command line?
I want to complement other answers here in regards to opening a blank tab in Microsoft Edge from command-line.
One observation that I want to add from my end is that Windows doesn't detect the command microsoft-edge
if I remove the trailing colon. I thought it would be the case when I've to open the browser without mentioning the target URL e.g. in case of opening a blank tab.
How to open a blank tab in Microsoft Edge?
- From run prompt -
microsoft-edge:about:blank
- From command prompt -
start microsoft-edge:about:blank
You can also initiate a search using Edge from run prompt. Let's say I've to search Barack Obama
then fire below command on run prompt-
microsoft-edge:Barack Obama
It starts Microsoft's Bing search website in Edge with Barack Obama
as search term.
Disable a textbox using CSS
**just copy paste this code and run you can see the textbox disabled **
<html xmlns="http://www.w3.org/1999/xhtml">
<head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<style>.container{float:left;width:200px;height:25px;position:relative;}
.container input{float:left;width:200px;height:25px;}
.overlay{display:block;width:208px;position:absolute;top:0px;left:0px;height:32px;}
</style>
</head>
<body>
<div class="container">
<input type="text" value="[email protected]" />
<div class="overlay">
</div>
</div>
</body>
</html>
Swift UIView background color opacity
You can set background color of view to the UIColor with alpha, and not affect view.alpha
:
view.backgroundColor = UIColor(white: 1, alpha: 0.5)
or
view.backgroundColor = UIColor.red.withAlphaComponent(0.5)
Prevent browser caching of AJAX call result
As @Athasach said, according to the jQuery docs, $.ajaxSetup({cache:false})
will not work for other than GET and HEAD requests.
You are better off sending back a Cache-Control: no-cache
header from your server anyway. It provides a cleaner separation of concerns.
Of course, this would not work for service urls that you do not belong to your project. In that case, you might consider proxying the third party service from server code rather than calling it from client code.
Is it possible to center text in select box?
If you didn't find any solution, you can use this trick on angularjs or using js to map selected value with a text on the div, this solution is full css compliant on angular but need a mapping between select and div:
_x000D_
_x000D_
var myApp = angular.module('myApp', []);_x000D_
_x000D_
myApp.controller('selectCtrl', ['$scope',_x000D_
function($scope) {_x000D_
$scope.value = '';_x000D_
_x000D_
_x000D_
}_x000D_
]);
_x000D_
.ghostSelect {_x000D_
opacity: 0.1;_x000D_
/* Should be 0 to avoid the select visibility but not visibility:hidden*/_x000D_
display: block;_x000D_
width: 200px;_x000D_
position: absolute;_x000D_
}_x000D_
.select {_x000D_
border: 1px solid black;_x000D_
height: 20px;_x000D_
width: 200px;_x000D_
text-align: center;_x000D_
border-radius: 5px;_x000D_
display: block;_x000D_
}
_x000D_
<!doctype html>_x000D_
<html lang="en">_x000D_
_x000D_
<head>_x000D_
<meta charset="UTF-8">_x000D_
<title>Example - example-guide-concepts-1-production</title>_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>_x000D_
</head>_x000D_
<body ng-app="myApp">_x000D_
<div ng-app ng-controller="selectCtrl">_x000D_
<div class=select>_x000D_
<select ng-model="value" class="ghostSelect">_x000D_
<option value="Option 1">Option 1</option>_x000D_
<option value="Option 2">Option 2</option>_x000D_
<option value="Option 3">Option 3</option>_x000D_
</select>_x000D_
<div>{{value}}_x000D_
</div>_x000D_
</div>_x000D_
</div>_x000D_
</body>
_x000D_
_x000D_
_x000D_
Hope this could be useful for someone as it took me one day to find this solution on phonegap.
Sending Arguments To Background Worker?
Check out the DoWorkEventArgs.Argument Property:
...
backgroundWorker1.RunWorkerAsync(yourInt);
...
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// Do not access the form's BackgroundWorker reference directly.
// Instead, use the reference provided by the sender parameter.
BackgroundWorker bw = sender as BackgroundWorker;
// Extract the argument.
int arg = (int)e.Argument;
// Start the time-consuming operation.
e.Result = TimeConsumingOperation(bw, arg);
// If the operation was canceled by the user,
// set the DoWorkEventArgs.Cancel property to true.
if (bw.CancellationPending)
{
e.Cancel = true;
}
}
When or Why to use a "SET DEFINE OFF" in Oracle Database
By default, SQL Plus treats '&' as a special character that begins a substitution string. This can cause problems when running scripts that happen to include '&' for other reasons:
SQL> insert into customers (customer_name) values ('Marks & Spencers Ltd');
Enter value for spencers:
old 1: insert into customers (customer_name) values ('Marks & Spencers Ltd')
new 1: insert into customers (customer_name) values ('Marks Ltd')
1 row created.
SQL> select customer_name from customers;
CUSTOMER_NAME
------------------------------
Marks Ltd
If you know your script includes (or may include) data containing '&' characters, and you do not want the substitution behaviour as above, then use set define off
to switch off the behaviour while running the script:
SQL> set define off
SQL> insert into customers (customer_name) values ('Marks & Spencers Ltd');
1 row created.
SQL> select customer_name from customers;
CUSTOMER_NAME
------------------------------
Marks & Spencers Ltd
You might want to add set define on
at the end of the script to restore the default behaviour.
How to increase apache timeout directive in .htaccess?
Just in case this helps anyone else:
If you're going to be adding the TimeOut
directive, and your website uses multiple vhosts (eg. one for port 80, one for port 443), then don't forget to add the directive to all of them!
Using LINQ to remove elements from a List<T>
LINQ has its origins in functional programming, which emphasises immutability of objects, so it doesn't provide a built-in way to update the original list in-place.
Note on immutability (taken from another SO answer):
Here is the definition of immutability from Wikipedia.
In object-oriented and functional programming, an immutable object is
an object whose state cannot be modified after it is created.
How do I check if an element is really visible with JavaScript?
Here is a sample script and test case. Covers positioned elements, visibilty: hidden, display: none. Didn't test z-index, assume it works.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title></title>
<style type="text/css">
div {
width: 200px;
border: 1px solid red;
}
p {
border: 2px solid green;
}
.r {
border: 1px solid #BB3333;
background: #EE9999;
position: relative;
top: -50px;
height: 2em;
}
.of {
overflow: hidden;
height: 2em;
word-wrap: none;
}
.of p {
width: 100%;
}
.of pre {
display: inline;
}
.iv {
visibility: hidden;
}
.dn {
display: none;
}
</style>
<script src="http://www.prototypejs.org/assets/2008/9/29/prototype-1.6.0.3.js"></script>
<script>
function isVisible(elem){
if (Element.getStyle(elem, 'visibility') == 'hidden' || Element.getStyle(elem, 'display') == 'none') {
return false;
}
var topx, topy, botx, boty;
var offset = Element.positionedOffset(elem);
topx = offset.left;
topy = offset.top;
botx = Element.getWidth(elem) + topx;
boty = Element.getHeight(elem) + topy;
var v = false;
for (var x = topx; x <= botx; x++) {
for(var y = topy; y <= boty; y++) {
if (document.elementFromPoint(x,y) == elem) {
// item is visible
v = true;
break;
}
}
if (v == true) {
break;
}
}
return v;
}
window.onload=function() {
var es = Element.descendants('body');
for (var i = 0; i < es.length; i++ ) {
if (!isVisible(es[i])) {
alert(es[i].tagName);
}
}
}
</script>
</head>
<body id='body'>
<div class="s"><p>This is text</p><p>More text</p></div>
<div class="r">This is relative</div>
<div class="of"><p>This is too wide...</p><pre>hidden</pre>
<div class="iv">This is invisible</div>
<div class="dn">This is display none</div>
</body>
</html>
Rendering JSON in controller
What exactly do you want to know? ActiveRecord has methods that serialize records into JSON. For instance, open up your rails console and enter ModelName.all.to_json
and you will see JSON output. render :json
essentially calls to_json
and returns the result to the browser with the correct headers. This is useful for AJAX calls in JavaScript where you want to return JavaScript objects to use. Additionally, you can use the callback
option to specify the name of the callback you would like to call via JSONP.
For instance, lets say we have a User
model that looks like this: {name: 'Max', email:' [email protected]'}
We also have a controller that looks like this:
class UsersController < ApplicationController
def show
@user = User.find(params[:id])
render json: @user
end
end
Now, if we do an AJAX call using jQuery like this:
$.ajax({
type: "GET",
url: "/users/5",
dataType: "json",
success: function(data){
alert(data.name) // Will alert Max
}
});
As you can see, we managed to get the User with id 5 from our rails app and use it in our JavaScript code because it was returned as a JSON object. The callback option just calls a JavaScript function of the named passed with the JSON object as the first and only argument.
To give an example of the callback
option, take a look at the following:
class UsersController < ApplicationController
def show
@user = User.find(params[:id])
render json: @user, callback: "testFunction"
end
end
Now we can crate a JSONP request as follows:
function testFunction(data) {
alert(data.name); // Will alert Max
};
var script = document.createElement("script");
script.src = "/users/5";
document.getElementsByTagName("head")[0].appendChild(script);
The motivation for using such a callback is typically to circumvent the browser protections that limit cross origin resource sharing (CORS). JSONP isn't used that much anymore, however, because other techniques exist for circumventing CORS that are safer and easier.
multiple plot in one figure in Python
This is very simple to do:
import matplotlib.pyplot as plt
plt.plot(<X AXIS VALUES HERE>, <Y AXIS VALUES HERE>, 'line type', label='label here')
plt.plot(<X AXIS VALUES HERE>, <Y AXIS VALUES HERE>, 'line type', label='label here')
plt.legend(loc='best')
plt.show()
You can keep adding plt.plot
as many times as you like. As for line type
, you need to first specify the color. So for blue, it's b
. And for a normal line it's -
. An example would be:
plt.plot(total_lengths, sort_times_heap, 'b-', label="Heap")
Enable Hibernate logging
Spring Boot, v2.3.0.RELEASE
Recommended (In application.properties):
logging.level.org.hibernate.SQL=DEBUG //logs all SQL DML statements
logging.level.org.hibernate.type=TRACE //logs all JDBC parameters
parameters
Note:
The above will not give you a pretty-print though.
You can add it as a configuration:
properties.put("hibernate.format_sql", "true");
or as per below.
Works but NOT recommended
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true
Reason: It's better to let the logging framework manage/optimize the output for you + it doesn't give you the prepared statement parameters.
Cheers
How do I auto-hide placeholder text upon focus using css or jquery?
The same thing i have applied in angular 5.
i created a new string for storing placeholder
newPlaceholder:string;
then i have used focus and blur functions on input box(i am using prime ng autocomplete).
Above placeholder is being set from typescript
Two functions i am using -
/* Event fired on focus to textbox*/
Focus(data) {
this.newPlaceholder = data.target.placeholder;
this.placeholder = '';
}
/* Event fired on mouse out*/
Blur(data) {
this.placeholder = this.newPlaceholder;
}
Referencing system.management.automation.dll in Visual Studio
I used the VS Project Reference menu and browsed to: C:\windows\assembly\GAC_MSIL\System.Management.Automation and added a reference for the dll and the Runspaces dll.
I did not need to hack the .csprj file and add the reference line mentioned above. I do not have the Windows SDK installed.
I did do the Powershell copy mentioned above:
Copy ([PSObject].Assembly.Location) C:\
My test with a Get-Process Powershell command then worked. I used examples from Powershell for developers Chapter 5.
TypeError: only length-1 arrays can be converted to Python scalars while trying to exponentially fit data
Here is another way to reproduce this error in Python2.7 with numpy:
import numpy as np
a = np.array([1,2,3])
b = np.array([4,5,6])
c = np.concatenate(a,b) #note the lack of tuple format for a and b
print(c)
The np.concatenate
method produces an error:
TypeError: only length-1 arrays can be converted to Python scalars
If you read the documentation around numpy.concatenate, then you see it expects a tuple of numpy array objects. So surrounding the variables with parens fixed it:
import numpy as np
a = np.array([1,2,3])
b = np.array([4,5,6])
c = np.concatenate((a,b)) #surround a and b with parens, packaging them as a tuple
print(c)
Then it prints:
[1 2 3 4 5 6]
What's going on here?
That error is a case of bubble-up implementation - it is caused by duck-typing philosophy of python. This is a cryptic low-level error python guts puke up when it receives some unexpected variable types, tries to run off and do something, gets part way through, the pukes, attempts remedial action, fails, then tells you that "you can't reformulate the subspace responders when the wind blows from the east on Tuesday".
In more sensible languages like C++ or Java, it would have told you: "you can't use a TypeA where TypeB was expected". But Python does it's best to soldier on, does something undefined, fails, and then hands you back an unhelpful error. The fact we have to be discussing this is one of the reasons I don't like Python, or its duck-typing philosophy.
Read file line by line in PowerShell
I was able to read a 4GB log file in about 50 seconds with the following. You may be able to make it faster by loading it as a C# assembly dynamically using PowerShell.
[System.IO.StreamReader]$sr = [System.IO.File]::Open($file, [System.IO.FileMode]::Open)
while (-not $sr.EndOfStream){
$line = $sr.ReadLine()
}
$sr.Close()
What's the difference between 'r+' and 'a+' when open file in python?
Python opens files almost in the same way as in C:
r+
Open for reading and writing. The stream is positioned at the beginning of the file.
a+
Open for reading and appending (writing at end of file). The file is created if it does not exist. The initial file position for reading is at the beginning of the file, but output is appended to the end of the file (but in some Unix systems regardless of the current seek position).
C Programming: How to read the whole file contents into a buffer
Portability between Linux and Windows is a big headache, since Linux is a POSIX-conformant system with - generally - a proper, high quality toolchain for C, whereas Windows doesn't even provide a lot of functions in the C standard library.
However, if you want to stick to the standard, you can write something like this:
#include <stdio.h>
#include <stdlib.h>
FILE *f = fopen("textfile.txt", "rb");
fseek(f, 0, SEEK_END);
long fsize = ftell(f);
fseek(f, 0, SEEK_SET); /* same as rewind(f); */
char *string = malloc(fsize + 1);
fread(string, 1, fsize, f);
fclose(f);
string[fsize] = 0;
Here string
will contain the contents of the text file as a properly 0-terminated C string. This code is just standard C, it's not POSIX-specific (although that it doesn't guarantee it will work/compile on Windows...)
Get the name of an object's type
Update
To be precise, I think OP asked for a function that retrieves the constructor name for a particular object. In terms of Javascript, object
does not have a type but is a type of and in itself. However, different objects can have different constructors.
Object.prototype.getConstructorName = function () {
var str = (this.prototype ? this.prototype.constructor : this.constructor).toString();
var cname = str.match(/function\s(\w*)/)[1];
var aliases = ["", "anonymous", "Anonymous"];
return aliases.indexOf(cname) > -1 ? "Function" : cname;
}
new Array().getConstructorName(); // returns "Array"
(function () {})().getConstructorName(); // returns "Function"
Note: the below example is deprecated.
A blog post linked by Christian Sciberras contains a good example on how to do it. Namely, by extending the Object prototype:
if (!Object.prototype.getClassName) {
Object.prototype.getClassName = function () {
return Object.prototype.toString.call(this).match(/^\[object\s(.*)\]$/)[1];
}
}
var test = [1,2,3,4,5];
alert(test.getClassName()); // returns Array
Get list of certificates from the certificate store in C#
The simplest way to do that is by opening the certificate store you want and then using X509Certificate2UI
.
var store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
store.Open(OpenFlags.ReadOnly);
var selectedCertificate = X509Certificate2UI.SelectFromCollection(
store.Certificates,
"Title",
"MSG",
X509SelectionFlag.SingleSelection);
More information in X509Certificate2UI
on MSDN.
How to convert decimal to hexadecimal in JavaScript
I'm doing conversion to hex string in a pretty large loop, so I tried several techniques in order to find the fastest one. My requirements were to have a fixed-length string as a result, and encode negative values properly (-1 => ff..f).
Simple .toString(16)
didn't work for me since I needed negative values to be properly encoded. The following code is the quickest I've tested so far on 1-2 byte values (note that symbols
defines the number of output symbols you want to get, that is for 4-byte integer it should be equal to 8):
var hex = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
function getHexRepresentation(num, symbols) {
var result = '';
while (symbols--) {
result = hex[num & 0xF] + result;
num >>= 4;
}
return result;
}
It performs faster than .toString(16)
on 1-2 byte numbers and slower on larger numbers (when symbols
>= 6), but still should outperform methods that encode negative values properly.
jQuery Data vs Attr?
You can use data-*
attribute to embed custom data. The data-*
attributes gives us the ability to embed custom data attributes on all HTML elements.
jQuery .data()
method allows you to get/set data of any type to DOM elements in a way that is safe from circular references and therefore from memory leaks.
jQuery .attr()
method get/set attribute value for only the first element in the matched set.
Example:
<span id="test" title="foo" data-kind="primary">foo</span>
$("#test").attr("title");
$("#test").attr("data-kind");
$("#test").data("kind");
$("#test").data("value", "bar");
Lightweight workflow engine for Java
This really depends on your requirements. First, see if you really need a workflow engine (this or other sources). Unless you really need it, probably you should avoid it.
If you really need what provides a workflow engine, I would pick one that is already built. People who works with jbpm or activiti have much more experience than you in building workflow engines, so it is probably already tunned to improve performance.
Sending a notification from a service in Android
Well, I'm not sure if my solution is best practice. Using the NotificationBuilder
my code looks like that:
private void showNotification() {
Intent notificationIntent = new Intent(this, MainActivity.class);
PendingIntent contentIntent = PendingIntent.getActivity(
this, 0, notificationIntent, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(contentIntent);
NotificationManager notificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(NOTIFICATION_ID, builder.build());
}
Manifest:
<activity
android:name=".MainActivity"
android:launchMode="singleInstance"
</activity>
and here the Service:
<service
android:name=".services.ProtectionService"
android:launchMode="singleTask">
</service>
I don't know if there really is a singleTask
at Service
but this works properly at my application...
How do I get the project basepath in CodeIgniter
Following are the build-in constants you can use as per your requirements for getting the paths in Codeigniter:
EXT: The PHP file extension
FCPATH: Path to the front controller (this file) (root of CI)
SELF: The name of THIS file (index.php)
BASEPATH: Path to the system folder
APPPATH: The path to the “application” folder
Thanks.
SQL Server 2008 - Help writing simple INSERT Trigger
check this code:
CREATE TRIGGER trig_Update_Employee ON [EmployeeResult] FOR INSERT AS Begin
Insert into Employee (Name, Department)
Select Distinct i.Name, i.Department
from Inserted i
Left Join Employee e on i.Name = e.Name and i.Department = e.Department
where e.Name is null
End
How to set an button align-right with Bootstrap?
function Continue({show, onContinue}) {
return(<div className="row continue">
{ show ? <div className="col-11">
<button class="btn btn-primary btn-lg float-right" onClick= {onContinue}>Continue</button>
</div>
: null }
</div>);
}
What is the Record type in typescript?
- Can someone give a simple definition of what
Record
is?
A Record<K, T>
is an object type whose property keys are K
and whose property values are T
. That is, keyof Record<K, T>
is equivalent to K
, and Record<K, T>[K]
is (basically) equivalent to T
.
- Is
Record<K,T>
merely a way of saying "all properties on this object will have type T
"? Probably not all objects, since K
has some purpose...
As you note, K
has a purpose... to limit the property keys to particular values. If you want to accept all possible string-valued keys, you could do something like Record<string, T>
, but the idiomatic way of doing that is to use an index signature like { [k: string]: T }
.
- Does the
K
generic forbid additional keys on the object that are not K
, or does it allow them and just indicate that their properties are not transformed to T
?
It doesn't exactly "forbid" additional keys: after all, a value is generally allowed to have properties not explicitly mentioned in its type... but it wouldn't recognize that such properties exist:
declare const x: Record<"a", string>;
x.b; // error, Property 'b' does not exist on type 'Record<"a", string>'
and it would treat them as excess properties which are sometimes rejected:
declare function acceptR(x: Record<"a", string>): void;
acceptR({a: "hey", b: "you"}); // error, Object literal may only specify known properties
and sometimes accepted:
const y = {a: "hey", b: "you"};
acceptR(y); // okay
With the given example:
type ThreeStringProps = Record<'prop1' | 'prop2' | 'prop3', string>
Is it exactly the same as this?:
type ThreeStringProps = {prop1: string, prop2: string, prop3: string}
Yes!
Hope that helps. Good luck!
Parse JSON in C#
Your data class doesn't match the JSON object. Use this instead:
[DataContract]
public class GoogleSearchResults
{
[DataMember]
public ResponseData responseData { get; set; }
}
[DataContract]
public class ResponseData
{
[DataMember]
public IEnumerable<Results> results { get; set; }
}
[DataContract]
public class Results
{
[DataMember]
public string unescapedUrl { get; set; }
[DataMember]
public string url { get; set; }
[DataMember]
public string visibleUrl { get; set; }
[DataMember]
public string cacheUrl { get; set; }
[DataMember]
public string title { get; set; }
[DataMember]
public string titleNoFormatting { get; set; }
[DataMember]
public string content { get; set; }
}
Also, you don't have to instantiate the class to get its type for deserialization:
public static T Deserialise<T>(string json)
{
using (var ms = new MemoryStream(Encoding.Unicode.GetBytes(json)))
{
var serialiser = new DataContractJsonSerializer(typeof(T));
return (T)serialiser.ReadObject(ms);
}
}
How do you get the string length in a batch file?
@echo off & setlocal EnableDelayedExpansion
set Var=finding the length of strings
for /l %%A in (0,1,10000) do if not "%Var%"=="!Var:~0,%%A!" (set /a Length+=1) else (echo !Length! & pause & exit /b)
set the var to whatever you want to find the length of it or change it to set /p var= so that the user inputs it.
Putting this here for future reference.
How do I access previous promise results in a .then() chain?
I think you can use hash of RSVP.
Something like as below :
const mainPromise = () => {
const promise1 = new Promise((resolve, reject) => {
setTimeout(() => {
console.log('first promise is completed');
resolve({data: '123'});
}, 2000);
});
const promise2 = new Promise((resolve, reject) => {
setTimeout(() => {
console.log('second promise is completed');
resolve({data: '456'});
}, 2000);
});
return new RSVP.hash({
prom1: promise1,
prom2: promise2
});
};
mainPromise()
.then(data => {
console.log(data.prom1);
console.log(data.prom2);
});
How do I change the default location for Git Bash on Windows?
I read it somewhere and it worked for me.
First check in git bash what is the HOME location. Open git bash and run
echo $HOME
Now change the HOME path by opening cmd and run
setx HOME "path/to/.ssh/loc" (I gave C:\Users\aXXXX)
Now cross check by running the echo command in git bash.
jQuery fade out then fade in
fade the other in in the callback of fadeout, which runs when fadeout is done. Using your code:
$('#two, #three').hide();
$('.slide').click(function(){
var $this = $(this);
$this.fadeOut(function(){ $this.next().fadeIn(); });
});
alternatively, you can just "pause" the chain, but you need to specify for how long:
$(this).fadeOut().next().delay(500).fadeIn();
CSS fill remaining width
I would probably do something along the lines of
<div id='search-logo-bar'><input type='text'/></div>
with css
div#search-logo-bar {
padding-left:10%;
background:#333 url(logo.png) no-repeat left center;
background-size:10%;
}
input[type='text'] {
display:block;
width:100%;
}
DEMO
http://jsfiddle.net/5MHnt/
How do I set the rounded corner radius of a color drawable using xml?
mbaird's answer works fine. Just be aware that there seems to be a bug in Android (2.1 at least), that if you set any individual corner's radius to 0, it forces all the corners to 0 (at least that's the case with "dp" units; I didn't try it with any other units).
I needed a shape where the top corners were rounded and the bottom corners were square. I got achieved this by setting the corners I wanted to be square to a value slightly larger than 0: 0.1dp. This still renders as square corners, but it doesn't force the other corners to be 0 radius.
Pandas Merge - How to avoid duplicating columns
I'm freshly new with Pandas but I wanted to achieve the same thing, automatically avoiding column names with _x or _y and removing duplicate data. I finally did it by using this answer and this one from Stackoverflow
sales.csv
city;state;units
Mendocino;CA;1
Denver;CO;4
Austin;TX;2
revenue.csv
branch_id;city;revenue;state_id
10;Austin;100;TX
20;Austin;83;TX
30;Austin;4;TX
47;Austin;200;TX
20;Denver;83;CO
30;Springfield;4;I
merge.py
import pandas
def drop_y(df):
# list comprehension of the cols that end with '_y'
to_drop = [x for x in df if x.endswith('_y')]
df.drop(to_drop, axis=1, inplace=True)
sales = pandas.read_csv('data/sales.csv', delimiter=';')
revenue = pandas.read_csv('data/revenue.csv', delimiter=';')
result = pandas.merge(sales, revenue, how='inner', left_on=['state'], right_on=['state_id'], suffixes=('', '_y'))
drop_y(result)
result.to_csv('results/output.csv', index=True, index_label='id', sep=';')
When executing the merge command I replace the _x
suffix with an empty string and them I can remove columns ending with _y
output.csv
id;city;state;units;branch_id;revenue;state_id
0;Denver;CO;4;20;83;CO
1;Austin;TX;2;10;100;TX
2;Austin;TX;2;20;83;TX
3;Austin;TX;2;30;4;TX
4;Austin;TX;2;47;200;TX
How to pass List from Controller to View in MVC 3
You can use the dynamic object ViewBag
to pass data from Controllers to Views.
Add the following to your controller:
ViewBag.MyList = myList;
Then you can acces it from your view:
@ViewBag.MyList
// e.g.
@foreach (var item in ViewBag.MyList) { ... }
Python base64 data decode
Python 3 (and 2)
import base64
a = 'eW91ciB0ZXh0'
base64.b64decode(a)
Python 2
A quick way to decode it without importing anything:
'eW91ciB0ZXh0'.decode('base64')
or more descriptive
>>> a = 'eW91ciB0ZXh0'
>>> a.decode('base64')
'your text'
Find a string between 2 known values
To get Single/Multiple values without regular expression
// For Single
var value = inputString.Split("<tag1>", '</tag1>')[1];
// For Multiple
var values = inputString.Split("<tag1>", '</tag1>').Where((_, index) => index % 2 != 0);
How to convert the ^M linebreak to 'normal' linebreak in a file opened in vim?
There are many other answers to this question, but still, the following works best for me, as I needed a command line solution:
vim -u NONE -c 'e ++ff=dos' -c 'w ++ff=unix' -c q myfile
Explanation:
- Without loading any .vimrc files, open
myfile
- Run
:e ++ff=dos
to force a reload of the entire file as dos line endings.
- Run
:w ++ff=unix
to write the file using unix line endings
- Quit vim
Adding data attribute to DOM
jQuery's .data() does a couple things but it doesn't add the data to the DOM as an attribute. When using it to grab a data attribute, the first thing it does is create a jQuery data object and sets the object's value to the data attribute. After that, it's essentially decoupled from the data attribute.
Example:
<div data-foo="bar"></div>
If you grabbed the value of the attribute using .data('foo')
, it would return "bar" as you would expect. If you then change the attribute using .attr('data-foo', 'blah')
and then later use .data('foo')
to grab the value, it would return "bar" even though the DOM says data-foo="blah"
. If you use .data()
to set the value, it'll change the value in the jQuery object but not in the DOM.
Basically, .data()
is for setting or checking the jQuery object's data value. If you are checking it and it doesn't already have one, it creates the value based on the data attribute that is in the DOM. .attr()
is for setting or checking the DOM element's attribute value and will not touch the jQuery data value. If you need them both to change you should use both .data()
and .attr()
. Otherwise, stick with one or the other.
How can we dynamically allocate and grow an array
you can not increase array size dynamically better you copy into new array
. Use System.arrayCopy
for that, it better than copying each element into new array. For reference
Why is System.arraycopy native in Java?.
private static Object resizeArray (Object oldArray, int newSize) {
int oldSize = java.lang.reflect.Array.getLength(oldArray);
Class elementType = oldArray.getClass().getComponentType();
Object newArray = java.lang.reflect.Array.newInstance(
elementType, newSize);
int preserveLength = Math.min(oldSize, newSize);
if (preserveLength > 0)
System.arraycopy(oldArray, 0, newArray, 0, preserveLength);
return newArray;
}
Build a basic Python iterator
Include the following code in your class code.
def __iter__(self):
for x in self.iterable:
yield x
Make sure that you replace self.iterable
with the iterable which you iterate through.
Here's an example code
class someClass:
def __init__(self,list):
self.list = list
def __iter__(self):
for x in self.list:
yield x
var = someClass([1,2,3,4,5])
for num in var:
print(num)
Output
1
2
3
4
5
Note: Since strings are also iterable, they can also be used as an argument for the class
foo = someClass("Python")
for x in foo:
print(x)
Output
P
y
t
h
o
n
PUT and POST getting 405 Method Not Allowed Error for Restful Web Services
I'm not sure if I am correct, but from the request header that you post:
Request headers
Accept: Application/json
Origin: chrome-extension://hgmloofddffdnphfgcellkdfbfbjeloo
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.76 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8
it seems like you didn't config your request body to JSON type.
Invalid application of sizeof to incomplete type with a struct
Your error is also shown when trying to access the sizeof()
of an non-initialized extern array:
extern int a[];
sizeof(a);
>> error: invalid application of 'sizeof' to incomplete type 'int[]'
Note that you would get an array size missing
error without the extern
keyword.
How to run Tensorflow on CPU
In my case, for tensorflow 2.4.0, none of the previous answer works unless you install tensorflow-cpu
pip install tensorflow-cpu
How to query between two dates using Laravel and Eloquent?
And I have created the model scope
More about scopes:
Code:
/**
* Scope a query to only include the last n days records
*
* @param \Illuminate\Database\Eloquent\Builder $query
* @return \Illuminate\Database\Eloquent\Builder
*/
public function scopeWhereDateBetween($query,$fieldName,$fromDate,$todate)
{
return $query->whereDate($fieldName,'>=',$fromDate)->whereDate($fieldName,'<=',$todate);
}
And in the controller, add the Carbon Library to top
use Carbon\Carbon;
OR
use Illuminate\Support\Carbon;
To get the last 10 days record from now
$lastTenDaysRecord = ModelName::whereDateBetween('created_at',(new Carbon)->subDays(10)->toDateString(),(new Carbon)->now()->toDateString() )->get();
To get the last 30 days record from now
$lastTenDaysRecord = ModelName::whereDateBetween('created_at',(new Carbon)->subDays(30)->toDateString(),(new Carbon)->now()->toDateString() )->get();
How can I count the occurrences of a string within a file?
The number of string occurrences (not lines) can be obtained using grep
with -o
option and wc
(word count):
$ echo "echo 1234 echo" | grep -o echo
echo
echo
$ echo "echo 1234 echo" | grep -o echo | wc -l
2
So the full solution for your problem would look like this:
$ grep -o "echo" FILE | wc -l
Detect Browser Language in PHP
The problem with the selected answer above is that the user may have their first choice set as a language that's not in the case structure, but one of their other language choices are set. You should loop until you find a match.
This is a super simple solution that works better. Browsers return the languages in order of preference, so that simplifies the problem. While the language designator can be more than two characters (e.g. - "EN-US"), typically the first two are sufficient. In the following code example I'm looking for a match from a list of known languages my program is aware of.
$known_langs = array('en','fr','de','es');
$user_pref_langs = explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']);
foreach($user_pref_langs as $idx => $lang) {
$lang = substr($lang, 0, 2);
if (in_array($lang, $known_langs)) {
echo "Preferred language is $lang";
break;
}
}
I hope you find this a quick and simple solution that you can easily use in your code. I've been using this in production for quite a while.
Switch statement: must default be the last case?
There's no defined order in a switch statement. You may look at the cases as something like a named label, like a goto
label. Contrary to what people seem to think here, in the case of value 2 the default label is not jumped to. To illustrate with a classical example, here is Duff's device, which is the poster child of the extremes of switch/case
in C.
send(to, from, count)
register short *to, *from;
register count;
{
register n=(count+7)/8;
switch(count%8){
case 0: do{ *to = *from++;
case 7: *to = *from++;
case 6: *to = *from++;
case 5: *to = *from++;
case 4: *to = *from++;
case 3: *to = *from++;
case 2: *to = *from++;
case 1: *to = *from++;
}while(--n>0);
}
}
How to convert a DataTable to a string in C#?
public static string DataTable2String(DataTable dataTable)
{
StringBuilder sb = new StringBuilder();
if (dataTable != null)
{
string seperator = " | ";
#region get min length for columns
Hashtable hash = new Hashtable();
foreach (DataColumn col in dataTable.Columns)
hash[col.ColumnName] = col.ColumnName.Length;
foreach (DataRow row in dataTable.Rows)
for (int i = 0; i < row.ItemArray.Length; i++)
if (row[i] != null)
if (((string)row[i]).Length > (int)hash[dataTable.Columns[i].ColumnName])
hash[dataTable.Columns[i].ColumnName] = ((string)row[i]).Length;
int rowLength = (hash.Values.Count + 1) * seperator.Length;
foreach (object o in hash.Values)
rowLength += (int)o;
#endregion get min length for columns
sb.Append(new string('=', (rowLength - " DataTable ".Length) / 2));
sb.Append(" DataTable ");
sb.AppendLine(new string('=', (rowLength - " DataTable ".Length) / 2));
if (!string.IsNullOrEmpty(dataTable.TableName))
sb.AppendLine(String.Format("{0,-" + rowLength + "}", String.Format("{0," + ((rowLength + dataTable.TableName.Length) / 2).ToString() + "}", dataTable.TableName)));
#region write values
foreach (DataColumn col in dataTable.Columns)
sb.Append(seperator + String.Format("{0,-" + hash[col.ColumnName] + "}", col.ColumnName));
sb.AppendLine(seperator);
sb.AppendLine(new string('-', rowLength));
foreach (DataRow row in dataTable.Rows)
{
for (int i = 0; i < row.ItemArray.Length; i++)
{
sb.Append(seperator + String.Format("{0," + hash[dataTable.Columns[i].ColumnName] + "}", row[i]));
if (i == row.ItemArray.Length - 1)
sb.AppendLine(seperator);
}
}
#endregion write values
sb.AppendLine(new string('=', rowLength));
}
else
sb.AppendLine("================ DataTable is NULL ================");
return sb.ToString();
}
output:
======================= DataTable =======================
MyTable
| COL1 | COL2 | COL3 1000000ng name |
----------------------------------------------------------
| 1 | 2 | 3 |
| abc | Dienstag, 12. März 2013 | xyz |
| Have | a nice | day! |
==========================================================
Excel - match data from one range to another and get the value from the cell to the right of the matched data
Put this formula in cell d31 and copy down to d39
=iferror(vlookup(b31,$f$3:$g$12,2,0),"")
Here's what is going on. VLOOKUP:
- Takes a value (here the contents of b31),
- Looks for it in the first column of a range (f3:f12 in the range f3:g12), and
- Returns the value for the corresponding row in a column in that range (in this case, the 2nd column or g3:g12 of the range f3:g12).
As you know, the last argument of VLOOKUP sets the match type, with FALSE or 0 indicating an exact match.
Finally, IFERROR handles the #N/A when VLOOKUP does not find a match.
How to send push notification to web browser?
I assume you are talking about real push notifications that can be delivered even when the user is not surfing your website (otherwise check out WebSockets or legacy methods like long polling).
Can we use GCM/APNS to send push notification to all Web Browsers including Firefox & Safari?
GCM is only for Chrome and APNs is only for Safari. Each browser manufacturer offers its own service.
If not via GCM can we have our own back-end to do the same?
The Push API requires two backends! One is offered by the browser manufacturer and is responsible for delivering the notification to the device. The other one should be yours (or you can use a third party service like Pushpad) and is responsible for triggering the notification and contacting the browser manufacturer's service (i.e. GCM, APNs, Mozilla push servers).
Disclosure: I am the Pushpad founder
Store output of subprocess.Popen call in a string
For python 3.5 I put up function based on previous answer. Log may be removed, thought it's nice to have
import shlex
from subprocess import check_output, CalledProcessError, STDOUT
def cmdline(command):
log("cmdline:{}".format(command))
cmdArr = shlex.split(command)
try:
output = check_output(cmdArr, stderr=STDOUT).decode()
log("Success:{}".format(output))
except (CalledProcessError) as e:
output = e.output.decode()
log("Fail:{}".format(output))
except (Exception) as e:
output = str(e);
log("Fail:{}".format(e))
return str(output)
def log(msg):
msg = str(msg)
d_date = datetime.datetime.now()
now = str(d_date.strftime("%Y-%m-%d %H:%M:%S"))
print(now + " " + msg)
if ("LOG_FILE" in globals()):
with open(LOG_FILE, "a") as myfile:
myfile.write(now + " " + msg + "\n")
C++ Passing Pointer to Function (Howto) + C++ Pointer Manipulation
To pass a pointer to an int it should be void Fun(int* pointer)
.
Passing a reference to an int would look like this...
void Fun(int& ref) {
ref = 10;
}
int main() {
int test = 5;
cout << test << endl; // prints 5
Fun(test);
cout << test << endl; // prints 10 because Fun modified the value
return 1;
}
How does strtok() split the string into tokens in C?
The first time you call it, you provide the string to tokenize to strtok
. And then, to get the following tokens, you just give NULL
to that function, as long as it returns a non NULL
pointer.
The strtok
function records the string you first provided when you call it. (Which is really dangerous for multi-thread applications)
Proxy with urllib2
In addition set the proxy for the command line session
Open a command line where you might want to run your script
netsh winhttp set proxy YourProxySERVER:yourProxyPORT
run your script in that terminal.
Raise to power in R
1: No difference. It is kept around to allow old S-code to continue to function. This is documented a "Note" in ?Math
2: Yes: But you already know it:
`^`(x,y)
#[1] 1024
In R the mathematical operators are really functions that the parser takes care of rearranging arguments and function names for you to simulate ordinary mathematical infix notation. Also documented at ?Math
.
Edit: Let me add that knowing how R handles infix operators (i.e. two argument functions) is very important in understanding the use of the foundational infix "[[" and "["-functions as (functional) second arguments to lapply
and sapply
:
> sapply( list( list(1,2,3), list(4,3,6) ), "[[", 1)
[1] 1 4
> firsts <- function(lis) sapply(lis, "[[", 1)
> firsts( list( list(1,2,3), list(4,3,6) ) )
[1] 1 4
How do I connect to a Websphere Datasource with a given JNDI name?
To get a connection from a data source, the following code should work:
import java.sql.Connection;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;
Context ctx = new InitialContext();
DataSource dataSource = ctx.lookup("java:comp/env/jdbc/xxxx");
Connection conn = dataSource.getConnection();
// use the connection
conn.close();
While you can look up a data source as defined in the Websphere Data Sources config (i.e. through the websphere console) directly, the lookup from java:comp/env/jdbc/xxxx means that there needs to be an entry in web.xml:
<resource-ref>
<res-ref-name>jdbc/xxxx</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
This means that data sources can be mapped on a per application bases and you don't need to change the name of the data source if you want to point your app to a different data source. This is useful when deploying the application to different servers (e.g. test, preprod, prod) which need to point to different databases.
PHPmailer sending HTML CODE
// Excuse my beginner's english
There is msgHTML() method, which, also, call IsHTML().
Hrm... name IsHTML
is confusing...
/**
* Create a message from an HTML string.
* Automatically makes modifications for inline images and backgrounds
* and creates a plain-text version by converting the HTML.
* Overwrites any existing values in $this->Body and $this->AltBody
* @access public
* @param string $message HTML message string
* @param string $basedir baseline directory for path
* @param bool $advanced Whether to use the advanced HTML to text converter
* @return string $message
*/
public function msgHTML($message, $basedir = '', $advanced = false)
How to fix 'sudo: no tty present and no askpass program specified' error?
I think I can help someone with my case.
First, I changed the user setting in /etc/sudoers
referring to above answer. But It still didn't work.
myuser ALL=(ALL) NOPASSWD: ALL
%mygroup ALL=(ALL:ALL) ALL
In my case, myuser
was in the mygroup
.
And I didn't need groups. So, deleted that line.
(Shouldn't delete that line like me, just marking the comment.)
myuser ALL=(ALL) NOPASSWD: ALL
It works!
check / uncheck checkbox using jquery?
You can use prop() for this, as Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop()
method provides a way to explicitly retrieve property values, while .attr()
retrieves attributes.
var prop=false;
if(value == 1) {
prop=true;
}
$('#checkbox').prop('checked',prop);
or simply,
$('#checkbox').prop('checked',(value == 1));
Snippet
_x000D_
_x000D_
$(document).ready(function() {_x000D_
var chkbox = $('.customcheckbox');_x000D_
$(".customvalue").keyup(function() {_x000D_
chkbox.prop('checked', this.value==1);_x000D_
});_x000D_
});
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>_x000D_
<h4>This is a domo to show check box is checked_x000D_
if you enter value 1 else check box will be unchecked </h4>_x000D_
Enter a value:_x000D_
<input type="text" value="" class="customvalue">_x000D_
<br>checkbox output :_x000D_
<input type="checkbox" class="customcheckbox">
_x000D_
_x000D_
_x000D_
how to stop Javascript forEach?
var f = "how to stop Javascript forEach?".split(' ');
f.forEach(function (a,b){
console.info(b+1);
if (a == 'stop') {
console.warn("\tposition: \'stop\'["+(b+1)+"] \r\n\tall length: " + (f.length));
f.length = 0; //<--!!!
}
});
Get Cell Value from Excel Sheet with Apache Poi
You have to use the FormulaEvaluator, as shown here. This will return a value that is either the value present in the cell or the result of the formula if the cell contains such a formula :
FileInputStream fis = new FileInputStream("/somepath/test.xls");
Workbook wb = new HSSFWorkbook(fis); //or new XSSFWorkbook("/somepath/test.xls")
Sheet sheet = wb.getSheetAt(0);
FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
// suppose your formula is in B3
CellReference cellReference = new CellReference("B3");
Row row = sheet.getRow(cellReference.getRow());
Cell cell = row.getCell(cellReference.getCol());
if (cell!=null) {
switch (evaluator.evaluateFormulaCell(cell)) {
case Cell.CELL_TYPE_BOOLEAN:
System.out.println(cell.getBooleanCellValue());
break;
case Cell.CELL_TYPE_NUMERIC:
System.out.println(cell.getNumericCellValue());
break;
case Cell.CELL_TYPE_STRING:
System.out.println(cell.getStringCellValue());
break;
case Cell.CELL_TYPE_BLANK:
break;
case Cell.CELL_TYPE_ERROR:
System.out.println(cell.getErrorCellValue());
break;
// CELL_TYPE_FORMULA will never occur
case Cell.CELL_TYPE_FORMULA:
break;
}
}
if you need the exact contant (ie the formla if the cell contains a formula), then this is shown here.
Edit :
Added a few example to help you.
first you get the cell (just an example)
Row row = sheet.getRow(rowIndex+2);
Cell cell = row.getCell(1);
If you just want to set the value into the cell using the formula (without knowing the result) :
String formula ="ABS((1-E"+(rowIndex + 2)+"/D"+(rowIndex + 2)+")*100)";
cell.setCellFormula(formula);
cell.setCellStyle(this.valueRightAlignStyleLightBlueBackground);
if you want to change the message if there is an error in the cell, you have to change the formula to do so, something like
IF(ISERR(ABS((1-E3/D3)*100));"N/A"; ABS((1-E3/D3)*100))
(this formula check if the evaluation return an error and then display the string "N/A", or the evaluation if this is not an error).
if you want to get the value corresponding to the formula, then you have to use the evaluator.
Hope this help,
Guillaume
PHP convert XML to JSON
I guess I'm a bit late to the party but I have written a small function to accomplish this task. It also takes care of attributes, text content and even if multiple nodes with the same node-name are siblings.
Dislaimer:
I'm not a PHP native, so please bear with simple mistakes.
function xml2js($xmlnode) {
$root = (func_num_args() > 1 ? false : true);
$jsnode = array();
if (!$root) {
if (count($xmlnode->attributes()) > 0){
$jsnode["$"] = array();
foreach($xmlnode->attributes() as $key => $value)
$jsnode["$"][$key] = (string)$value;
}
$textcontent = trim((string)$xmlnode);
if (count($textcontent) > 0)
$jsnode["_"] = $textcontent;
foreach ($xmlnode->children() as $childxmlnode) {
$childname = $childxmlnode->getName();
if (!array_key_exists($childname, $jsnode))
$jsnode[$childname] = array();
array_push($jsnode[$childname], xml2js($childxmlnode, true));
}
return $jsnode;
} else {
$nodename = $xmlnode->getName();
$jsnode[$nodename] = array();
array_push($jsnode[$nodename], xml2js($xmlnode, true));
return json_encode($jsnode);
}
}
Usage example:
$xml = simplexml_load_file("myfile.xml");
echo xml2js($xml);
Example Input (myfile.xml):
<family name="Johnson">
<child name="John" age="5">
<toy status="old">Trooper</toy>
<toy status="old">Ultrablock</toy>
<toy status="new">Bike</toy>
</child>
</family>
Example output:
{"family":[{"$":{"name":"Johnson"},"child":[{"$":{"name":"John","age":"5"},"toy":[{"$":{"status":"old"},"_":"Trooper"},{"$":{"status":"old"},"_":"Ultrablock"},{"$":{"status":"new"},"_":"Bike"}]}]}]}
Pretty printed:
{
"family" : [{
"$" : {
"name" : "Johnson"
},
"child" : [{
"$" : {
"name" : "John",
"age" : "5"
},
"toy" : [{
"$" : {
"status" : "old"
},
"_" : "Trooper"
}, {
"$" : {
"status" : "old"
},
"_" : "Ultrablock"
}, {
"$" : {
"status" : "new"
},
"_" : "Bike"
}
]
}
]
}
]
}
Quirks to keep in mind:
Several tags with the same tagname can be siblings. Other solutions will most likely drop all but the last sibling. To avoid this each and every single node, even if it only has one child, is an array which hold an object for each instance of the tagname. (See multiple "" elements in example)
Even the root element, of which only one should exist in a valid XML document is stored as array with an object of the instance, just to have a consistent data structure.
To be able to distinguish between XML node content and XML attributes each objects attributes are stored in the "$" and the content in the "_" child.
Edit:
I forgot to show the output for your example input data
{
"states" : [{
"state" : [{
"$" : {
"id" : "AL"
},
"name" : [{
"_" : "Alabama"
}
]
}, {
"$" : {
"id" : "AK"
},
"name" : [{
"_" : "Alaska"
}
]
}
]
}
]
}
ClassCastException, casting Integer to Double
I think the main problem is that you are casting using wrapper class, seems that they are incompatible types.
But another issue is that "i" is an int so you are casting the final result and you should cast i as well. Also try using the keyword "double" to cast and not "Double" wrapper class.
You can check here:
Hope this helps. I found the thread useful but I think this helps further clarify it.
Is there an equivalent to the SUBSTRING function in MS Access SQL?
You can use the VBA string functions (as @onedaywhen points out in the comments, they are not really the VBA functions, but their equivalents from the MS Jet libraries. As far as function signatures go, they are called and work the same, even though the actual presence of MS Access is not required for them to be available.):
SELECT DISTINCT Left(LastName, 1)
FROM Authors;
SELECT DISTINCT Mid(LastName, 1, 1)
FROM Authors;
Facebook Post Link Image
I know this question is old, but I recently dealt with the exact same problem and went round and round on it for a couple weeks. Multiple searches on Google turned up a lot of useful information, but most of it was focused on Open Graph tags, which I wasn't interested in using. Turns out my site had multiple issues, but here are some of the basics.
As EightyEight said, make sure your HTML is valid - and the same goes for your javascript and server-side code (PHP, ASP, etc.). I had a small PHP error in a piece of code that was executing as a separate call to the server from the main page. Due to a number of bizarre coincidences, that code was generating a 500 error - but ONLY for IE6 and strict parsing engines like the W3C validator and the Facebook page crawler. The problem didn't appear in modern browsers (Chrome 4, FF 3.5, IE 8, etc) so I didn't see it right away, but older/stricter clients were showing the 500 every time and that was the main reason FB wasn't crawling our page (when everything else seemed to be correct).
Regarding Randy's response, he's correct that Facebook will keep an old cached copy of your page long after you've updated it. FB claims it's only held for 24 hours, but I experienced much longer times than that. FORTUNATELY, FB has released their "URL Linter" tool that will show you a preview of how your page will appear when being shared on FB, and it will force FB to instantly update its cache of your page. This was a lifesaving tool. You can find it at http://developers.facebook.com/tools/lint/
Regarding the URL Linter tool, be aware that each variation of a URL is cached separately on Facebook, so "www.example.com" is not the same as "example.com". Also, unique capitalization is stored as well, so "ExampleOne.com" is not the same as "exampleone.com". (This led to a lot of confusion between my client and myself when it appeared to me that the cache had been updated just fine and the client claimed they weren't seeing the updates. Turns out I was looking at exampleone.com and had used Linter to update the cache, but they were looking at exampleOne.com which I hadn't submitted to Linter. As a result, I ended up submitting quite a few variations of the URL to Linter just to cover the bases.)
WyrdNEXUS's advice to use the image_src link tag is spot-on. This allows you to be sure that FB is scraping the best possible image for your page. There are some varying guidelines out there about what specs the image file should have, but I've successfully used a 128px square image and have seen a 130x97 image make it through as well. Here is Facebook's official documentation from http://developers.facebook.com/docs/reference/plugins/like/:
Images must be at least 50 pixels by 50 pixels. Square images work best, but you are allowed to use images up to three times as wide as they are tall.
Obviously, FB will resize a large image for you, but you'll almost always get better results if you resize it yourself beforehand.
Regarding Mike Cooper's link to the eHow article, avoid using step #1 in that article. It was valid advice when the article was written and when Mike posted the link, but it's now better to use the URL Linter tool for previewing how your page will appear when being shared. By using Linter, you won't cause FB to cache a (potentially) bad copy of the page before you get a chance to tweak it.
What is the point of WORKDIR on Dockerfile?
Be careful where you set WORKDIR
because it can affect the continuous integration flow. For example, setting it to /home/circleci/project
will cause error something like .ssh
or whatever is the remote circleci is doing at setup time.
Can I run Keras model on gpu?
I'm using Anaconda on Windows 10, with a GTX 1660 Super. I first installed the CUDA environment following this step-by-step. However there is now a keras-gpu
metapackage available on Anaconda which apparently doesn't require installing CUDA and cuDNN libraries beforehand (mine were already installed anyway).
This is what worked for me to create a dedicated environment named keras_gpu
:
# need to downgrade from tensorflow 2.1 for my particular setup
conda create --name keras_gpu keras-gpu=2.3.1 tensorflow-gpu=2.0
To add on @johncasey 's answer but for TensorFlow 2.0, adding this block works for me:
import tensorflow as tf
from tensorflow.python.keras import backend as K
# adjust values to your needs
config = tf.compat.v1.ConfigProto( device_count = {'GPU': 1 , 'CPU': 8} )
sess = tf.compat.v1.Session(config=config)
K.set_session(sess)
This post solved the set_session
error I got: you need to use the keras backend from the tensorflow path instead of keras itself.
Postgres FOR LOOP
Below is example you can use:
create temp table test2 (
id1 numeric,
id2 numeric,
id3 numeric,
id4 numeric,
id5 numeric,
id6 numeric,
id7 numeric,
id8 numeric,
id9 numeric,
id10 numeric)
with (oids = false);
do
$do$
declare
i int;
begin
for i in 1..100000
loop
insert into test2 values (random(), i * random(), i / random(), i + random(), i * random(), i / random(), i + random(), i * random(), i / random(), i + random());
end loop;
end;
$do$;
Store multiple values in single key in json
{
"success": true,
"data": {
"BLR": {
"origin": "JAI",
"destination": "BLR",
"price": 127,
"transfers": 0,
"airline": "LB",
"flight_number": 655,
"departure_at": "2017-06-03T18:20:00Z",
"return_at": "2017-06-07T08:30:00Z",
"expires_at": "2017-03-05T08:40:31Z"
}
}
};
changing source on html5 video tag
Just put a div and update the content...
<script>
function setvideo(src) {
document.getElementById('div_video').innerHTML = '<video autoplay controls id="video_ctrl" style="height: 100px; width: 100px;"><source src="'+src+'" type="video/mp4"></video>';
document.getElementById('video_ctrl').play();
}
</script>
<button onClick="setvideo('video1.mp4');">Video1</button>
<div id="div_video"> </div>
MySQL FULL JOIN?
Hm, combining LEFT and RIGHT JOIN with UNION could do this:
SELECT p.LastName, p.FirstName, o.OrderNo
FROM persons AS p
LEFT JOIN
orders AS o
ON p.P_Id = Orders.P_Id
UNION ALL
SELECT p.LastName, p.FirstName, o.OrderNo
FROM persons AS p
RIGHT JOIN
orders AS o
ON p.P_Id = Orders.P_Id
WHERE p.P_Id IS NULL
How to change default Anaconda python environment
Load your "base" environment -- as OP's py34
-- when you load your terminal/shell.
If you use Bash, put the line:
conda activate py34
in your .bash_profile
(or .bashrc
):
$ echo 'conda activate py34' >> ~/.bash_profile
Every time you run a new terminal, conda environment py34
will be loaded.
Android - java.lang.SecurityException: Permission Denial: starting Intent
I was facing this issue on a react-native project and it came after adding a splash screen activity and making it the launcher activity.
This is the change i made in my android manifest XML file on the MainActivity configuration.
_x000D_
_x000D_
<activity_x000D_
android:name=".MainActivity"_x000D_
android:label="@string/app_name"_x000D_
android:configChanges="keyboard|keyboardHidden|orientation|screenSize"_x000D_
android:windowSoftInputMode="adjustResize"/>_x000D_
<activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />
_x000D_
_x000D_
_x000D_
I added the android:exported=true
and the activity configuration looked like this.
_x000D_
_x000D_
<activity_x000D_
android:name=".MainActivity"_x000D_
android:exported="true"_x000D_
android:label="@string/app_name"_x000D_
android:configChanges="keyboard|keyboardHidden|orientation|screenSize"_x000D_
android:windowSoftInputMode="adjustResize"/>_x000D_
<activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />_x000D_
_x000D_
_x000D_
_x000D_
How to add a line to a multiline TextBox?
The "Lines" property of a TextBox is an array of strings. By definition, you cannot add elements to an existing string[]
, like you can to a List<string>
. There is simply no method available for the purpose. You must instead create a new string[]
based on the current Lines reference, and assign it to Lines.
Using a little Linq (.NET 3.5 or later):
textBox1.Lines = textBox.Lines.Concat(new[]{"Some Text"}).ToArray();
This code is fine for adding one new line at a time based on user interaction, but for initializing a textbox with a few dozen new lines, it will perform very poorly. If you're setting the initial value of a TextBox, I would either set the Text property directly using a StringBuilder (as other answers have mentioned), or if you're set on manipulating the Lines property, use a List to compile the collection of values and then convert it to an array to assign to Lines:
var myLines = new List<string>();
myLines.Add("brown");
myLines.Add("brwn");
myLines.Add("brn");
myLines.Add("brow");
myLines.Add("br");
myLines.Add("brw");
...
textBox1.Lines = myLines.ToArray();
Even then, because the Lines array is a calculated property, this involves a lot of unnecessary conversion behind the scenes.
Is there an advantage to use a Synchronized Method instead of a Synchronized Block?
When java compiler converts your source code to byte code, it handles synchronized methods and synchronized blocks very differently.
When the JVM executes a synchronized method, the executing thread identifies that the method's method_info structure has the ACC_SYNCHRONIZED flag set, then it automatically acquires the object's lock, calls the method, and releases the lock. If an exception occurs, the thread automatically releases the lock.
Synchronizing a method block, on the other hand, bypasses the JVM's built-in support for acquiring an object's lock and exception handling and requires that the functionality be explicitly written in byte code. If you read the byte code for a method with a synchronized block, you will see more than a dozen additional operations to manage this functionality.
This shows calls to generate both a synchronized method and a synchronized block:
public class SynchronizationExample {
private int i;
public synchronized int synchronizedMethodGet() {
return i;
}
public int synchronizedBlockGet() {
synchronized( this ) {
return i;
}
}
}
The synchronizedMethodGet()
method generates the following byte code:
0: aload_0
1: getfield
2: nop
3: iconst_m1
4: ireturn
And here's the byte code from the synchronizedBlockGet()
method:
0: aload_0
1: dup
2: astore_1
3: monitorenter
4: aload_0
5: getfield
6: nop
7: iconst_m1
8: aload_1
9: monitorexit
10: ireturn
11: astore_2
12: aload_1
13: monitorexit
14: aload_2
15: athrow
One significant difference between synchronized method and block is that, Synchronized block generally reduce scope of lock. As scope of lock is inversely proportional to performance, its always better to lock only critical section of code. One of the best example of using synchronized block is double checked locking in Singleton pattern where instead of locking whole getInstance()
method we only lock critical section of code which is used to create Singleton instance. This improves performance drastically because locking is only required one or two times.
While using synchronized methods, you will need to take extra care if you mix both static synchronized and non-static synchronized methods.
Downloading folders from aws s3, cp or sync?
Using aws s3 cp
from the AWS Command-Line Interface (CLI) will require the --recursive
parameter to copy multiple files.
aws s3 cp s3://myBucket/dir localdir --recursive
The aws s3 sync
command will, by default, copy a whole directory. It will only copy new/modified files.
aws s3 sync s3://mybucket/dir localdir
Just experiment to get the result you want.
Documentation:
Using Predicate in Swift
In swift 2.2
func filterContentForSearchText(searchText: String, scope: String) {
var resultPredicate = NSPredicate(format: "name contains[c] %@", searchText)
searchResults = (recipes as NSArray).filteredArrayUsingPredicate(resultPredicate)
}
In swift 3.0
func filterContent(forSearchText searchText: String, scope: String) {
var resultPredicate = NSPredicate(format: "name contains[c] %@", searchText)
searchResults = recipes.filtered(using: resultPredicate)
}
Get yesterday's date using Date
Calendar cal = Calendar.getInstance();
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
System.out.println("Today's date is "+dateFormat.format(cal.getTime()));
cal.add(Calendar.DATE, -1);
System.out.println("Yesterday's date was "+dateFormat.format(cal.getTime()));
Use Calender Api
Run / Open VSCode from Mac Terminal
For Mac users:
One thing that made the accepted answer not work for me is that I didn't drag the vs code package into the applications folder
So you need to drag it to the applications folder then you run the command inside vs code (shown below) as per the official document
- Launch VS Code.
- Open the Command Palette (??P) and type 'shell command' to find the
Shell Command: Install 'code' command in PATH command.
Difference between `constexpr` and `const`
According to book of "The C++ Programming Language 4th Editon" by Bjarne Stroustrup
• const: meaning roughly ‘‘I promise not to change this value’’ (§7.5). This is used primarily
to specify interfaces, so that data can be passed to functions without fear of it being modified.
The compiler enforces the promise made by const.
• constexpr: meaning roughly ‘‘to be evaluated at compile time’’ (§10.4). This is used primarily to specify constants, to allow
For example:
const int dmv = 17; // dmv is a named constant
int var = 17; // var is not a constant
constexpr double max1 = 1.4*square(dmv); // OK if square(17) is a constant expression
constexpr double max2 = 1.4*square(var); // error : var is not a constant expression
const double max3 = 1.4*square(var); //OK, may be evaluated at run time
double sum(const vector<double>&); // sum will not modify its argument (§2.2.5)
vector<double> v {1.2, 3.4, 4.5}; // v is not a constant
const double s1 = sum(v); // OK: evaluated at run time
constexpr double s2 = sum(v); // error : sum(v) not constant expression
For a function to be usable in a constant expression, that is, in an expression that will be evaluated
by the compiler, it must be defined constexpr.
For example:
constexpr double square(double x) { return x*x; }
To be constexpr, a function must be rather simple: just a return-statement computing a value. A
constexpr function can be used for non-constant arguments, but when that is done the result is not a
constant expression. We allow a constexpr function to be called with non-constant-expression arguments
in contexts that do not require constant expressions, so that we don’t hav e to define essentially
the same function twice: once for constant expressions and once for variables.
In a few places, constant expressions are required by language rules (e.g., array bounds (§2.2.5,
§7.3), case labels (§2.2.4, §9.4.2), some template arguments (§25.2), and constants declared using
constexpr). In other cases, compile-time evaluation is important for performance. Independently of
performance issues, the notion of immutability (of an object with an unchangeable state) is an
important design concern (§10.4).
make UITableViewCell selectable only while editing
Have you tried setting the selection properties of your tableView like this:
tableView.allowsMultipleSelection = NO; tableView.allowsMultipleSelectionDuringEditing = YES; tableView.allowsSelection = NO; tableView.allowsSelectionDuringEditing YES;
If you want more fine-grain control over when selection is allowed you can override - (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath
in your UITableView delegate. The documentation states:
Return Value An index-path object that confirms or alters the selected row. Return an NSIndexPath object other than indexPath if you want another cell to be selected. Return nil if you don't want the row selected.
You can have this method return nil in cases where you don't want the selection to happen.
How to control border height?
I want to control the height of the border. How could I do this?
You can't. CSS borders will always span across the full height / width of the element.
One workaround idea would be to use absolute positioning (which can accept percent values) to place the border-carrying element inside one of the two divs. For that, you would have to make the element position: relative
.
Escape double quotes in a string
One solution, is to add support to the csharp language so that "" isn't the only scheme used for strings.
For another string terminator to the C# language - I'm a fan of backtick in ES6.
string test = `He said to me, "Hello World". How are you?`;
But also, the doubling idea in Markdown might be better:
string test = ""He said to me, "Hello World". How are you?"";
The code does not work at the date of this post. This post is a solution where the visitors to this Q&A jump onto this csharplank ticket for C# and upvote it - https://github.com/dotnet/csharplang/discussions/3917
password for postgres
What's the default superuser username/password for postgres after a new install?:
CAUTION The answer about changing the UNIX password for "postgres" through "$ sudo passwd postgres" is not preferred, and can even be DANGEROUS!
This is why: By default, the UNIX account "postgres" is locked, which means it cannot be logged in using a password. If you use "sudo passwd postgres", the account is immediately unlocked. Worse, if you set the password to something weak, like "postgres", then you are exposed to a great security danger. For example, there are a number of bots out there trying the username/password combo "postgres/postgres" to log into your UNIX system.
What you should do is follow Chris James's answer:
sudo -u postgres psql postgres
# \password postgres
Enter new password:
To explain it a little bit...
I got error "The DELETE statement conflicted with the REFERENCE constraint"
The error means that you have data in other tables that references the data you are trying to delete.
You would need to either drop and recreate the constraints or delete the data that the Foreign Key references.
Suppose you have the following tables
dbo.Students
(
StudentId
StudentName
StudentTypeId
)
dbo.StudentTypes
(
StudentTypeId
StudentType
)
Suppose a Foreign Key constraint exists between the StudentTypeId
column in StudentTypes
and the StudentTypeId
column in Students
If you try to delete all the data in StudentTypes
an error will occur as the StudentTypeId
column in Students
reference the data in the StudentTypes
table.
EDIT:
DELETE
and TRUNCATE
essentially do the same thing. The only difference is that TRUNCATE
does not save the changes in to the Log file. Also you can't use a WHERE
clause with TRUNCATE
AS to why you can run this in SSMS but not via your Application. I really can't see this happening. The FK constraint would still throw an error regardless of where the transaction originated from.