Programs & Examples On #Dot matrix

Random number c++ in some range

float RandomFloat(float min, float max)
{
    float r = (float)rand() / (float)RAND_MAX;
    return min + r * (max - min);
}

Is it possible to Turn page programmatically in UIPageViewController?

As @samwize pointed out, the way of paginating is by using

setViewControllers:array

Here's the way I did it: I have my datasource and the delegate separate. You can call this method and only change the "next" view. Previously you have to apply the paging rules. That is, you have to check direction and the next controller. If you use that method with your custom datasource the array of controllers that you're displaying won't change (since you'll use a custom array on a NSObject subclass).

Using your own datasource the method just sets a new view (with specific direction). Since you will still controll the pages that will display when normally swiping.

Creating a .p12 file

The openssl documentation says that file supplied as the -in argument must be in PEM format.

Turns out that, contrary to the CA's manual, the certificate returned by the CA which I stored in myCert.cer is not PEM format rather it is PKCS7.

In order to create my .p12, I had to first convert the certificate to PEM:

openssl pkcs7 -in myCert.cer -print_certs -out certs.pem

and then execute

openssl pkcs12 -export -out keyStore.p12 -inkey myKey.pem -in certs.pem

Postgresql column reference "id" is ambiguous

SELECT (vg.id, name) FROM v_groups vg 
INNER JOIN people2v_groups p2vg ON vg.id = p2vg.v_group_id
WHERE p2vg.people_id = 0;

How to delete Certain Characters in a excel 2010 cell

Another option: =MID(A1,2,LEN(A1)-2)

Or this (for fun): =RIGHT(LEFT(A1,LEN(A1)-1),LEN(LEFT(A1,LEN(A1)-1))-1)

Freezing Row 1 and Column A at the same time

Select cell B2 and click "Freeze Panes" this will freeze Row 1 and Column A.

For future reference, selecting Freeze Panes in Excel will freeze the rows above your selected cell and the columns to the left of your selected cell. For example, to freeze rows 1 and 2 and column A, you could select cell B3 and click Freeze Panes. You could also freeze columns A and B and row 1, by selecting cell C2 and clicking "Freeze Panes".

Visual Aid on Freeze Panes in Excel 2010 - http://www.dummies.com/how-to/content/how-to-freeze-panes-in-an-excel-2010-worksheet.html

Microsoft Reference Guide (More Complicated, but resourceful none the less) - http://office.microsoft.com/en-us/excel-help/freeze-or-lock-rows-and-columns-HP010342542.aspx

Launching a website via windows commandline

This worked for me:

explorer <YOUR URL>

For example:

explorer "https://www.google.com/"

This will open https://www.google.com/ in your default browser.

how to fix Cannot call sendRedirect() after the response has been committed?

you can't call sendRedirect(), after you have already used forward(). So, you get that exception.

How to install XNA game studio on Visual Studio 2012?

Yes, it's possible with a bit of tweak. Unfortunately, you still have to have VS 2010 installed.

  1. First, install XNA Game Studio 4.0. The easiest way is to install the Windows Phone SDK 7.1 which contains everything required.

  2. Copy the XNA Game Extension from VS 10 to VS 11 by opening a command prompt 'as administrator' and executing the following (may vary if not x64 computer with defaults paths) :

    xcopy /e "C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\Extensions\Microsoft\XNA Game Studio 4.0" "C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\Extensions\Microsoft\XNA Game Studio 4.0"

  3. Run notepad as administrator then open extension.vsixmanifest in the destination directory just created.

  4. Upgrade the Supported product version to match the new version (or duplicate the whole VisualStudio element and change the Version attribute, as @brainslugs83 said in comments):

    <SupportedProducts>
      <VisualStudio Version="11.0">
        <Edition>VSTS</Edition>
        <Edition>VSTD</Edition>
        <Edition>Pro</Edition>
        <Edition>VCSExpress</Edition>
        <Edition>VPDExpress</Edition>
      </VisualStudio>
    </SupportedProducts>
    
  5. Don't forget to clear/delete your cache in %localappdata%\Microsoft\VisualStudio\12.0\Extensions.

  6. You may have to run the command to tells Visual Studio that new extensions are available. If you see an 'access denied' message, try launching the console as an administrator.

    "C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\devenv.exe" /setup
    

This has been tested for Windows Games, but not WP7 or Xbox games.

[Edit] According Jowsty, this works also for XBox 360 Games.

[Edit for Visual Studio 2013 & Windows 8.1] See here for documentation on installing Windows Phone SDK 7.1 on Windows 8.1. Use VS version number 12.0 in place of 11.0 for all of these steps, and they will still work correctly.

Split a String into an array in Swift?

Swift 4 or later

If you just need to properly format a person name, you can use PersonNameComponentsFormatter.

The PersonNameComponentsFormatter class provides localized representations of the components of a person’s name, as represented by a PersonNameComponents object. Use this class to create localized names when displaying person name information to the user.


// iOS (9.0 and later), macOS (10.11 and later), tvOS (9.0 and later), watchOS (2.0 and later)
let nameFormatter = PersonNameComponentsFormatter()

let name =  "Mr. Steven Paul Jobs Jr."
// personNameComponents requires iOS (10.0 and later)
if let nameComps  = nameFormatter.personNameComponents(from: name) {
    nameComps.namePrefix   // Mr.
    nameComps.givenName    // Steven
    nameComps.middleName   // Paul
    nameComps.familyName   // Jobs
    nameComps.nameSuffix   // Jr.

    // It can also be configured to format your names
    // Default (same as medium), short, long or abbreviated

    nameFormatter.style = .default
    nameFormatter.string(from: nameComps)   // "Steven Jobs"

    nameFormatter.style = .short
    nameFormatter.string(from: nameComps)   // "Steven"

    nameFormatter.style = .long
    nameFormatter.string(from: nameComps)   // "Mr. Steven Paul Jobs jr."

    nameFormatter.style = .abbreviated
    nameFormatter.string(from: nameComps)   // SJ

    // It can also be use to return an attributed string using annotatedString method
    nameFormatter.style = .long
    nameFormatter.annotatedString(from: nameComps)   // "Mr. Steven Paul Jobs jr."
}

enter image description here

edit/update:

Swift 5 or later

For just splitting a string by non letter characters we can use the new Character property isLetter:

let fullName = "First Last"

let components = fullName.split{ !$0.isLetter }
print(components)  // "["First", "Last"]\n"

Set value of textarea in jQuery

There the problem : I need to generate html code from the contain of a given div. Then, I have to put this raw html code in a textarea. When I use the function $(textarea).val() like this :

$(textarea).val("some html like < input type='text' value='' style="background: url('http://www.w.com/bg.gif') repeat-x center;" /> bla bla");

or

$('#idTxtArGenHtml').val( $('idDivMain').html() );

I had problem with some special character ( & ' " ) when they are between quot. But when I use the function : $(textarea).html() the text is ok.

There an example form :

<FORM id="idFormContact" name="nFormContact" action="send.php" method="post"  >
    <FIELDSET id="idFieldContact" class="CMainFieldset">
        <LEGEND>Test your newsletter&raquo; </LEGEND> 
        <p>Send to &agrave; : <input id='idInpMailList' type='text' value='[email protected]' /></p>
        <FIELDSET  class="CChildFieldset">
            <LEGEND>Subject</LEGEND>
            <LABEL for="idNomClient" class="CInfoLabel">Enter the subject: *&nbsp</LABEL><BR/>
          <INPUT value="" name="nSubject" type="text" id="idSubject" class="CFormInput" alt="Enter the Subject" ><BR/>
    </FIELDSET>
    <FIELDSET  class="CChildFieldset">
        <INPUT id="idBtnGen" type="button" value="Generate" onclick="onGenHtml();"/>&nbsp;&nbsp;
          <INPUT id="idBtnSend" type="button" value="Send" onclick="onSend();"/><BR/><BR/>
            <LEGEND>Message</LEGEND>
                <LABEL for="idTxtArGenHtml" class="CInfoLabel">Html code : *&nbsp</LABEL><BR/>
                <span><TEXTAREA  name="nTxtArGenHtml" id="idTxtArGenHtml" width='100%' cols="69" rows="300" alt="enter your message" ></TEXTAREA></span>
        </FIELDSET>
    </FIELDSET>
</FORM>

And javascript/jquery code that don't work to fill the textarea is :

function onGenHtml(){
  $('#idTxtArGenHtml').html( $("#idDivMain").html()  );
}

Finaly the solution :

function onGenHtml(){
  $('#idTxtArGenHtml').html( $("#idDivMain").html() );
  $('#idTxtArGenHtml').parent().replaceWith( '<span>'+$('#idTxtArGenHtml').parent().html()+'</span>');
}

The trick is wrap your textarea with a span tag to help with the replaceWith function. I'm not sure if it's very clean, but it's work perfect too add raw html code in a textarea.

JFrame Maximize window

Provided that you are extending JFrame:

public void run() {
    MyFrame myFrame = new MyFrame();
    myFrame.setVisible(true);
    myFrame.setExtendedState(myFrame.getExtendedState() | JFrame.MAXIMIZED_BOTH);
}

How can I view the source code for a function?

There is a very handy function in R edit

new_optim <- edit(optim)

It will open the source code of optim using the editor specified in R's options, and then you can edit it and assign the modified function to new_optim. I like this function very much to view code or to debug the code, e.g, print some messages or variables or even assign them to a global variables for further investigation (of course you can use debug).

If you just want to view the source code and don't want the annoying long source code printed on your console, you can use

invisible(edit(optim))

Clearly, this cannot be used to view C/C++ or Fortran source code.

BTW, edit can open other objects like list, matrix, etc, which then shows the data structure with attributes as well. Function de can be used to open an excel like editor (if GUI supports it) to modify matrix or data frame and return the new one. This is handy sometimes, but should be avoided in usual case, especially when you matrix is big.

What to put in a python module docstring?

To quote the specifications:

The docstring of a script (a stand-alone program) should be usable as its "usage" message, printed when the script is invoked with incorrect or missing arguments (or perhaps with a "-h" option, for "help"). Such a docstring should document the script's function and command line syntax, environment variables, and files. Usage messages can be fairly elaborate (several screens full) and should be sufficient for a new user to use the command properly, as well as a complete quick reference to all options and arguments for the sophisticated user.

The docstring for a module should generally list the classes, exceptions and functions (and any other objects) that are exported by the module, with a one-line summary of each. (These summaries generally give less detail than the summary line in the object's docstring.) The docstring for a package (i.e., the docstring of the package's __init__.py module) should also list the modules and subpackages exported by the package.

The docstring for a class should summarize its behavior and list the public methods and instance variables. If the class is intended to be subclassed, and has an additional interface for subclasses, this interface should be listed separately (in the docstring). The class constructor should be documented in the docstring for its __init__ method. Individual methods should be documented by their own docstring.

The docstring of a function or method is a phrase ending in a period. It prescribes the function or method's effect as a command ("Do this", "Return that"), not as a description; e.g. don't write "Returns the pathname ...". A multiline-docstring for a function or method should summarize its behavior and document its arguments, return value(s), side effects, exceptions raised, and restrictions on when it can be called (all if applicable). Optional arguments should be indicated. It should be documented whether keyword arguments are part of the interface.

How to check if another instance of my shell script is running

pidof wasn't working for me so I searched some more and came across pgrep

for pid in $(pgrep -f my_script.sh); do
    if [ $pid != $$ ]; then
        echo "[$(date)] : my_script.sh : Process is already running with PID $pid"
        exit 1
    else
      echo "Running with PID $pid"
    fi  
done

Taken in part from answers above and https://askubuntu.com/a/803106/802276

Where do I call the BatchNormalization function in Keras?

Batch Normalization is used to normalize the input layer as well as hidden layers by adjusting mean and scaling of the activations. Because of this normalizing effect with additional layer in deep neural networks, the network can use higher learning rate without vanishing or exploding gradients. Furthermore, batch normalization regularizes the network such that it is easier to generalize, and it is thus unnecessary to use dropout to mitigate overfitting.

Right after calculating the linear function using say, the Dense() or Conv2D() in Keras, we use BatchNormalization() which calculates the linear function in a layer and then we add the non-linearity to the layer using Activation().

from keras.layers.normalization import BatchNormalization
model = Sequential()
model.add(Dense(64, input_dim=14, init='uniform'))
model.add(BatchNormalization(epsilon=1e-06, mode=0, momentum=0.9, weights=None))
model.add(Activation('tanh'))
model.add(Dropout(0.5))
model.add(Dense(64, init='uniform'))
model.add(BatchNormalization(epsilon=1e-06, mode=0, momentum=0.9, weights=None))
model.add(Activation('tanh'))
model.add(Dropout(0.5))
model.add(Dense(2, init='uniform'))
model.add(BatchNormalization(epsilon=1e-06, mode=0, momentum=0.9, weights=None))
model.add(Activation('softmax'))

sgd = SGD(lr=0.1, decay=1e-6, momentum=0.9, nesterov=True)
model.compile(loss='binary_crossentropy', optimizer=sgd)
model.fit(X_train, y_train, nb_epoch=20, batch_size=16, show_accuracy=True, 
validation_split=0.2, verbose = 2)

How is Batch Normalization applied?

Suppose we have input a[l-1] to a layer l. Also we have weights W[l] and bias unit b[l] for the layer l. Let a[l] be the activation vector calculated(i.e. after adding the non-linearity) for the layer l and z[l] be the vector before adding non-linearity

  1. Using a[l-1] and W[l] we can calculate z[l] for the layer l
  2. Usually in feed-forward propagation we will add bias unit to the z[l] at this stage like this z[l]+b[l], but in Batch Normalization this step of addition of b[l] is not required and no b[l] parameter is used.
  3. Calculate z[l] means and subtract it from each element
  4. Divide (z[l] - mean) using standard deviation. Call it Z_temp[l]
  5. Now define new parameters ? and ß that will change the scale of the hidden layer as follows:

    z_norm[l] = ?.Z_temp[l] + ß

In this code excerpt, the Dense() takes the a[l-1], uses W[l] and calculates z[l]. Then the immediate BatchNormalization() will perform the above steps to give z_norm[l]. And then the immediate Activation() will calculate tanh(z_norm[l]) to give a[l] i.e.

a[l] = tanh(z_norm[l])

Prevent typing non-numeric in input type number

The other answers seemed more complicated than necessary so I adapted their answers to this short and sweet function.

function allowOnlyNumbers(event) {
  if (event.key.length === 1 && /\D/.test(event.key)) {
    event.preventDefault();
  }
}

It won't do change the behavior of any arrow, enter, shift, ctrl or tab keys because the length of the key property for those events is longer than a single character. It also uses a simple regular expressions to look for any non digit character.

How do you find the first key in a dictionary?

Use a for loop that ranges through all keys in prices:

for key, value in prices.items():
     print key
     print "price: %s" %value

Make sure that you change prices.items() to prices.iteritems() if you're using Python 2.x

How to make a node.js application run permanently?

You could simply use this

nohup node /srv/www/MyUserAccount/server/server.js &

This will keep the application running and to shut it down you will have to kill it.

For that you could install htop and then search for node and then kill it

How to convert XML to JSON in Python?

xmltodict (full disclosure: I wrote it) can help you convert your XML to a dict+list+string structure, following this "standard". It is Expat-based, so it's very fast and doesn't need to load the whole XML tree in memory.

Once you have that data structure, you can serialize it to JSON:

import xmltodict, json

o = xmltodict.parse('<e> <a>text</a> <a>text</a> </e>')
json.dumps(o) # '{"e": {"a": ["text", "text"]}}'

How to get an MD5 checksum in PowerShell

Here are the two lines, just change "hello" in line #2:

PS C:\> [Reflection.Assembly]::LoadWithPartialName("System.Web")
PS C:\> [System.Web.Security.FormsAuthentication]::HashPasswordForStoringInConfigFile("hello", "MD5")

Complex numbers usage in python

The following example for complex numbers should be self explanatory including the error message at the end

>>> x=complex(1,2)
>>> print x
(1+2j)
>>> y=complex(3,4)
>>> print y
(3+4j)
>>> z=x+y
>>> print x
(1+2j)
>>> print z
(4+6j)
>>> z=x*y
>>> print z
(-5+10j)
>>> z=x/y
>>> print z
(0.44+0.08j)
>>> print x.conjugate()
(1-2j)
>>> print x.imag
2.0
>>> print x.real
1.0
>>> print x>y

Traceback (most recent call last):
  File "<pyshell#149>", line 1, in <module>
    print x>y
TypeError: no ordering relation is defined for complex numbers
>>> print x==y
False
>>> 

jQuery multiselect drop down menu

I've used jQuery MultiSelect for implementing multiselect drop down menu with checkbox. You can see the implementation guide from here - Multi-select Dropdown List with Checkbox

Implementation is very simple, need only using the following code.

$('#transactionType').multiselect({
    columns: 1,
    placeholder: 'Select Transaction Type'
});

Deleting Row in SQLite in Android

if you are using SQLiteDatabase then there is a delete method

Definition of Delete

int delete (String table, String whereClause, String[] whereArgs)

Example Implementation

Now we can write a method called delete with argument as name

public void delete(String value) {
    db.delete(DATABASE_TABLE, KEY_NAME + "=?", new String[]{String.valueOf(value)});
}

if you want to delete all records then just pass null to the above method,

public void delete() {
    db.delete(DATABASE_TABLE, null, null);
}

Source Of Information

Tensorflow 2.0 - AttributeError: module 'tensorflow' has no attribute 'Session'

TF2 runs Eager Execution by default, thus removing the need for Sessions. If you want to run static graphs, the more proper way is to use tf.function() in TF2. While Session can still be accessed via tf.compat.v1.Session() in TF2, I would discourage using it. It may be helpful to demonstrate this difference by comparing the difference in hello worlds:

TF1.x hello world:

import tensorflow as tf
msg = tf.constant('Hello, TensorFlow!')
sess = tf.Session()
print(sess.run(msg))

TF2.x hello world:

import tensorflow as tf
msg = tf.constant('Hello, TensorFlow!')
tf.print(msg)

For more info, see Effective TensorFlow 2

Print Currency Number Format in PHP

The easiest answer is number_format().

echo "$ ".number_format($value, 2);

If you want your application to be able to work with multiple currencies and locale-aware formatting (1.000,00 for some of us Europeans for example), it becomes a bit more complex.

There is money_format() but it doesn't work on Windows and relies on setlocale(), which is rubbish in my opinion, because it requires the installation of (arbitrarily named) locale packages on server side.

If you want to seriously internationalize your application, consider using a full-blown internationalization library like Zend Framework's Zend_Locale and Zend_Currency.

Building executable jar with maven?

If you don't want execute assembly goal on package, you can use next command:

mvn package assembly:single

Here package is keyword.

How to start working with GTest and CMake

The OP is using Windows, and a much easier way to use GTest today is with vcpkg+cmake.


Install vcpkg as per https://github.com/microsoft/vcpkg , and make sure you can run vcpkg from the cmd line. Take note of the vcpkg installation folder, eg. C:\bin\programs\vcpkg.

Install gtest using vcpkg install gtest: this will download, compile, and install GTest.

Use a CmakeLists.txt as below: note we can use targets instead of including folders.

cmake_minimum_required(VERSION 3.15)
project(sample CXX)
enable_testing()
find_package(GTest REQUIRED)
add_executable(test1 test.cpp source.cpp)
target_link_libraries(test1 GTest::GTest GTest::Main)
add_test(test-1 test1)

Run cmake with: (edit the vcpkg folder if necessary, and make sure the path to the vcpkg.cmake toolchain file is correct)

cmake -B build -DCMAKE_TOOLCHAIN_FILE=C:\bin\programs\vcpkg\scripts\buildsystems\vcpkg.cmake

and build using cmake --build build as usual. Note that, vcpkg will also copy the required gtest(d).dll/gtest(d)_main.dll from the install folder to the Debug/Release folders.

Test with cd build & ctest.

Spring Bean Scopes

Detailed explanation for each scope can be found here in Spring bean scopes. Below is the summary

Singleton - (Default) Scopes a single bean definition to a single object instance per Spring IoC container.

prototype - Scopes a single bean definition to any number of object instances.

request - Scopes a single bean definition to the lifecycle of a single HTTP request; that is, each HTTP request has its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring ApplicationContext.

session - Scopes a single bean definition to the lifecycle of an HTTP Session. Only valid in the context of a web-aware Spring ApplicationContext.

global session - Scopes a single bean definition to the lifecycle of a global HTTP Session. Typically only valid when used in a portlet context. Only valid in the context of a web-aware Spring ApplicationContext.

How to use http.client in Node.js if there is basic authorization

for what it's worth I'm using node.js 0.6.7 on OSX and I couldn't get 'Authorization':auth to work with our proxy, it needed to be set to 'Proxy-Authorization':auth my test code is:

var http = require("http");
var auth = 'Basic ' + new Buffer("username:password").toString('base64');
var options = {
    host: 'proxyserver',
    port: 80,
    method:"GET",
    path: 'http://www.google.com',
    headers:{
        "Proxy-Authorization": auth,
        Host: "www.google.com"
    } 
};
http.get(options, function(res) {
    console.log(res);
    res.pipe(process.stdout);
});

Using jQuery to build table rows from AJAX response(json)

Here is a complete answer from hmkcode.com

If we have such JSON data

// JSON Data
var articles = [
    { 
        "title":"Title 1",
        "url":"URL 1",
        "categories":["jQuery"],
        "tags":["jquery","json","$.each"]
    },
    {
        "title":"Title 2",
        "url":"URL 2",
        "categories":["Java"],
        "tags":["java","json","jquery"]
    }
];

And we want to view in this Table structure

<table id="added-articles" class="table">
            <tr>
                <th>Title</th>
                <th>Categories</th>
                <th>Tags</th>
            </tr>
        </table>

The following JS code will fill create a row for each JSON element

// 1. remove all existing rows
$("tr:has(td)").remove();

// 2. get each article
$.each(articles, function (index, article) {

    // 2.2 Create table column for categories
    var td_categories = $("<td/>");

    // 2.3 get each category of this article
    $.each(article.categories, function (i, category) {
        var span = $("<span/>");
        span.text(category);
        td_categories.append(span);
    });

    // 2.4 Create table column for tags
   var td_tags = $("<td/>");

    // 2.5 get each tag of this article    
    $.each(article.tags, function (i, tag) {
        var span = $("<span/>");
        span.text(tag);
        td_tags.append(span);
    });

    // 2.6 Create a new row and append 3 columns (title+url, categories, tags)
    $("#added-articles").append($('<tr/>')
            .append($('<td/>').html("<a href='"+article.url+"'>"+article.title+"</a>"))
            .append(td_categories)
            .append(td_tags)
    ); 
});  

Removing page title and date when printing web page (with CSS?)

Its simple. Just use css.

<style>
@page { size: auto;  margin: 0mm; }
</style>

FormData.append("key", "value") is not working

In my case on Edge browser:

  const formData = new FormData(this.form);
  for (const [key, value] of formData.entries()) {
      formObject[key] = value;
  }

give me the same error

So I'm not using FormData and i just manually build an object

import React from 'react';    
import formDataToObject from 'form-data-to-object';

  ...

let formObject = {};

// EDGE compatibility -  replace FormData by
for (let i = 0; i < this.form.length; i++) {
  if (this.form[i].name) {
    formObject[this.form[i].name] = this.form[i].value;
  }
}

const data = formDataToObject.toObj(formObject): // convert "user[email]":"[email protected]" => "user":{"email":"[email protected]"}

const orderRes = await fetch(`/api/orders`, {
        method: 'POST',
        credentials: 'same-origin',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(data)
      });

const order = await orderRes.json();

Disable Enable Trigger SQL server for a table

I wanted to share something that helped me out. Idea credit goes to @Siavash and @Shahab Naseer.

I needed something where I could script disable and re enable of triggers for a particular table. I normally try and stay away from tiggers, but sometimes they could be good to use.

I took the script above and added a join to the sysobjects so I could filter by table name. This script will disable a trigger or triggers for a table.

select 'alter table '+ (select Schema_name(schema_id) from sys.objects o 
where o.object_id = parent_id) + '.'+object_name(parent_id) + ' ENABLE TRIGGER '+ t.Name as EnableScript,*
from sys.triggers t 
INNER JOIN dbo.sysobjects DS ON DS.id = t.parent_id 
where is_disabled = 0 AND DS.name = 'tblSubContact'

Support for the experimental syntax 'classProperties' isn't currently enabled

I faced the same issue while trying to transpile some jsx with babel. Below is the solution that worked for me. You can add the following json to your .babelrc

{
  "presets": [
    [
      "@babel/preset-react",
      { "targets": { "browsers": ["last 3 versions", "safari >= 6"] } }
    ]
  ],
  "plugins": [["@babel/plugin-proposal-class-properties"]]
}

Correct way to handle conditional styling in React

 <div style={{ visibility: this.state.driverDetails.firstName != undefined? 'visible': 'hidden'}}></div>

Checkout the above code. That will do the trick.

JavaScript hide/show element

If you are using it in a table use this :-

  <script type="text/javascript">
   function showStuff(id, text, btn) {
    document.getElementById(id).style.display = 'table-row';
    // hide the lorem ipsum text
    document.getElementById(text).style.display = 'none';
    // hide the link
    btn.style.display = 'none';
}
</script>


<td class="post">

<a href="#" onclick="showStuff('answer1', 'text1', this); return false;">Edit</a>
<span id="answer1" style="display: none;">
<textarea rows="10" cols="115"></textarea>
</span>

<span id="text1">Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum</span>
</td>

Current Subversion revision command

I think I have to do svn info and then retrieve the number with a string manipulation from "Revision: xxxxxx" It would be just nice, if there were a command that returns just the number :)

Submitting form and pass data to controller method of type FileStreamResult

You seem to be specifying the form to use a HTTP 'GET' request using FormMethod.Get. This will not work unless you tell it to do a post as that is what you seem to want the ActionResult to do. This will probably work by changing FormMethod.Get to FormMethod.Post.

As well as this you may also want to think about how Get and Post requests work and how these interact with the Model.

javascript check for not null

It is possibly because the value of val is actually the string "null" rather than the value null.

run program in Python shell

From the same folder, you can do:

import test

How can I get a list of users from active directory?

Include the System.DirectoryServices.dll, then use the code below:

DirectoryEntry directoryEntry = new DirectoryEntry("WinNT://" + Environment.MachineName);
string userNames="Users: ";

foreach (DirectoryEntry child in directoryEntry.Children)
{
    if (child.SchemaClassName == "User")
    {
        userNames += child.Name + Environment.NewLine   ;         
    }

}
MessageBox.Show(userNames);

Parsing a CSV file using NodeJS

I used this way:-

var fs = require('fs'); 
var parse = require('csv-parse');

var csvData=[];
fs.createReadStream(req.file.path)
    .pipe(parse({delimiter: ':'}))
    .on('data', function(csvrow) {
        console.log(csvrow);
        //do something with csvrow
        csvData.push(csvrow);        
    })
    .on('end',function() {
      //do something with csvData
      console.log(csvData);
    });

JSON Array iteration in Android/Java

If you're using the JSON.org Java implementation, which is open source, you can just make JSONArray implement the Iterable interface and add the following method to the class:

@Override
public Iterator iterator() {
    return this.myArrayList.iterator();
}

This will make all instances of JSONArray iterable, meaning that the for (Object foo : bar) syntax will now work with it (note that foo has to be an Object, because JSONArrays do not have a declared type). All this works because the JSONArray class is backed by a simple ArrayList, which is already iterable. I imagine that other open source implementations would be just as easy to change.

How to position text over an image in css

A small and short way of doing the same

HTML

<div class="image">
     <p>
        <h3>Heading 3</h3>
        <h5>Heading 5</h5>
     </p>
</div>

CSS

.image {
        position: relative;
        margin-bottom: 20px;
        width: 100%;
        height: 300px;
        color: white;
        background: url('../../Images/myImg.jpg') no-repeat;
        background-size: 250px 250px;
    }

How do you auto format code in Visual Studio?

Cut/Paste of a section is another quick way (and easy to remember).

node.js - request - How to "emitter.setMaxListeners()"?

Try to use:

require('events').EventEmitter.defaultMaxListeners = Infinity; 

How do I tell CMake to link in a static library in the source directory?

I found this helpful...

http://www.cmake.org/pipermail/cmake/2011-June/045222.html

From their example:

ADD_LIBRARY(boost_unit_test_framework STATIC IMPORTED)
SET_TARGET_PROPERTIES(boost_unit_test_framework PROPERTIES IMPORTED_LOCATION /usr/lib/libboost_unit_test_framework.a)
TARGET_LINK_LIBRARIES(mytarget A boost_unit_test_framework C)

Path.Combine for URLs?

An easy way to combine them and ensure it's always correct is:

string.Format("{0}/{1}", Url1.Trim('/'), Url2);

Read a file line by line assigning the value to a variable

The following reads a file passed as an argument line by line:

while IFS= read -r line; do
    echo "Text read from file: $line"
done < my_filename.txt

This is the standard form for reading lines from a file in a loop. Explanation:

  • IFS= (or IFS='') prevents leading/trailing whitespace from being trimmed.
  • -r prevents backslash escapes from being interpreted.

Or you can put it in a bash file helper script, example contents:

#!/bin/bash
while IFS= read -r line; do
    echo "Text read from file: $line"
done < "$1"

If the above is saved to a script with filename readfile, it can be run as follows:

chmod +x readfile
./readfile filename.txt

If the file isn’t a standard POSIX text file (= not terminated by a newline character), the loop can be modified to handle trailing partial lines:

while IFS= read -r line || [[ -n "$line" ]]; do
    echo "Text read from file: $line"
done < "$1"

Here, || [[ -n $line ]] prevents the last line from being ignored if it doesn't end with a \n (since read returns a non-zero exit code when it encounters EOF).

If the commands inside the loop also read from standard input, the file descriptor used by read can be chanced to something else (avoid the standard file descriptors), e.g.:

while IFS= read -r -u3 line; do
    echo "Text read from file: $line"
done 3< "$1"

(Non-Bash shells might not know read -u3; use read <&3 instead.)

Change bar plot colour in geom_bar with ggplot2 in r

If you want all the bars to get the same color (fill), you can easily add it inside geom_bar.

ggplot(data=df, aes(x=c1+c2/2, y=c3)) + 
geom_bar(stat="identity", width=c2, fill = "#FF6666")

enter image description here

Add fill = the_name_of_your_var inside aes to change the colors depending of the variable :

c4 = c("A", "B", "C")
df = cbind(df, c4)
ggplot(data=df, aes(x=c1+c2/2, y=c3, fill = c4)) + 
geom_bar(stat="identity", width=c2)

enter image description here

Use scale_fill_manual() if you want to manually the change of colors.

ggplot(data=df, aes(x=c1+c2/2, y=c3, fill = c4)) + 
geom_bar(stat="identity", width=c2) + 
scale_fill_manual("legend", values = c("A" = "black", "B" = "orange", "C" = "blue"))

enter image description here

using lodash .groupBy. how to add your own keys for grouped output?

Here is an updated version using lodash 4 and ES6

const result = _.chain(data)
    .groupBy("color")
    .toPairs()
    .map(pair => _.zipObject(['color', 'users'], pair))
    .value();

What properties can I use with event.target?

//Do it like---
function dragStart(this_,event) {
    var row=$(this_).attr('whatever');
    event.dataTransfer.setData("Text", row);
}

Getting the IP address of the current machine using Java

This could be a bit tricky in the most general case.

On the face of it, InetAddress.getLocalHost() should give you the IP address of this host. The problem is that a host could have lots of network interfaces, and an interface could be bound to more than one IP address. And to top that, not all IP addresses will be reachable outside of your machine or your LAN. For example, they could be IP addresses for virtual network devices, private network IP addresses, and so on.

What this means is that the IP address returned by InetAddress.getLocalHost() might not be the right one to use.

How can you deal with this?

  • One approach is to use NetworkInterface.getNetworkInterfaces() to get all of the known network interfaces on the host, and then iterate over each NI's addresses.
  • Another approach is to (somehow) get the externally advertized FQDN for the host, and use InetAddress.getByName() to look up the primary IP address. (But how do you get it, and how do you deal with a DNS-based load balancer?)
  • A variation of the previous is to get the preferred FQDN from a config file or a command line parameter.
  • Another variation is to get the preferred IP address from a config file or a command line parameter.

In summary, InetAddress.getLocalHost() will typically work, but you may need to provide an alternative method for the cases where your code is run in an environment with "complicated" networking.


I am able to get all the IP addresses associated all Network Interfaces, but how do i distinguish them?

  • Any address in the range 127.xxx.xxx.xxx is a "loopback" address. It is only visible to "this" host.
  • Any address in the range 192.168.xxx.xxx is a private (aka site local) IP address. These are reserved for use within an organization. The same applies to 10.xxx.xxx.xxx addresses, and 172.16.xxx.xxx through 172.31.xxx.xxx.
  • Addresses in the range 169.254.xxx.xxx are link local IP addresses. These are reserved for use on a single network segment.
  • Addresses in the range 224.xxx.xxx.xxx through 239.xxx.xxx.xxx are multicast addresses.
  • The address 255.255.255.255 is the broadcast address.
  • Anything else should be a valid public point-to-point IPv4 address.

In fact, the InetAddress API provides methods for testing for loopback, link local, site local, multicast and broadcast addresses. You can use these to sort out which of the IP addresses you get back is most appropriate.

Xcode swift am/pm time to 24 hour format

Just convert it to a date using NSDateFormatter and the "h:mm a" format and convert it back to a string using the "HH:mm" format. Check out this date formatting guide to familiarize yourself with this material.

enter image description here

let dateAsString = "6:35 PM"
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "h:mm a"
let date = dateFormatter.dateFromString(dateAsString)

dateFormatter.dateFormat = "HH:mm"
let date24 = dateFormatter.stringFromDate(date!)

Check if current date is between two dates Oracle SQL

TSQL: Dates- need to look for gaps in dates between Two Date

select
distinct
e1.enddate,
e3.startdate,
DATEDIFF(DAY,e1.enddate,e3.startdate)-1 as [Datediff]
from #temp e1 
   join #temp e3 on e1.enddate < e3.startdate          
       /* Finds the next start Time */
and e3.startdate = (select min(startdate) from #temp e5
where e5.startdate > e1.enddate)
and not exists (select *  /* Eliminates e1 rows if it is overlapped */
from #temp e5 
where e5.startdate < e1.enddate and e5.enddate > e1.enddate);

Could not load type from assembly error

Is the assembly in the Global Assembly Cache (GAC) or any place the might be overriding the assembly that you think is being loaded? This is usually the result of an incorrect assembly being loaded, for me it means I usually have something in the GAC overriding the version I have in bin/Debug.

How to make vim paste from (and copy to) system's clipboard?

I ran into this issue on a mid-2017 Macbook Pro running vim within iTerm2 as my primary development environment.

As other answers have suggested, I ran vim --version and noticed that it returns -clipboard, which means that the version of vim that shipped with my machine hasn't been compiled with the clipboard option.

The homebrew package for vim appears to compile with the clipboard option, so the fix for me was to:

  1. Run brew install vim
  2. Add set clipboard+=unnamed to my ~/.vimrc file
  3. Close and reopen iTerm2

How do I clear the previous text field value after submitting the form with out refreshing the entire page?

.val() or .value is IMHO the best solution because it's useful with Ajax. And .reset() only works after page reload and APIs using Ajax never refresh pages unless it's triggered by a different script.

What's the difference between JavaScript and Java?

Like everybody's saying, they're pretty much entirely different.

However, if you need a scripting language for your Java application, Javascript is actually a really good choice. There are ways to get Javascript running in the JVM and you can access and manipulate Java classes pretty seamlessly once you do.

Jquery DatePicker Set default date

use defaultDate()

Set the date to highlight on first opening if the field is blank. Specify either an actual date via a Date object or as a string in the current [[UI/Datepicker#option-dateFormat|dateFormat]], or a number of days from today (e.g. +7) or a string of values and periods ('y' for years, 'm' for months, 'w' for weeks, 'd' for days, e.g. '+1m +7d'), or null for today.

try this

$("[name=trainingStartFromDate]").datepicker({ dateFormat: 'dd-mm-yy', changeYear: true,defaultDate: new Date()});
$("[name=trainingStartToDate]").datepicker({ dateFormat: 'dd-mm-yy', changeYear: true,defaultDate: +15}); 

Eclipse CDT: Symbol 'cout' could not be resolved

For me it helped to enable the automated discovery in Properties -> C/C++-Build -> Discovery Options to resolve this problem.

Uncaught TypeError : cannot read property 'replace' of undefined In Grid

Please try with the below code snippet.

<!DOCTYPE html>
<html>
<head>
    <title>Test</title>
    <link href="http://cdn.kendostatic.com/2014.1.318/styles/kendo.common.min.css" rel="stylesheet" />
    <link href="http://cdn.kendostatic.com/2014.1.318/styles/kendo.default.min.css" rel="stylesheet" />
    <script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
    <script src="http://cdn.kendostatic.com/2014.1.318/js/kendo.all.min.js"></script>
    <script>
        function onDataBound(e) {
            var grid = $("#grid").data("kendoGrid");
            $(grid.tbody).find('tr').removeClass('k-alt');
        }

        $(document).ready(function () {
            $("#grid").kendoGrid({
                dataSource: {
                    type: "odata",
                    transport: {
                        read: "http://demos.telerik.com/kendo-ui/service/Northwind.svc/Orders"
                    },
                    schema: {
                        model: {
                            fields: {
                                OrderID: { type: "number" },
                                Freight: { type: "number" },
                                ShipName: { type: "string" },
                                OrderDate: { type: "date" },
                                ShipCity: { type: "string" }
                            }
                        }
                    },
                    pageSize: 20,
                    serverPaging: true,
                    serverFiltering: true,
                    serverSorting: true
                },
                height: 430,
                filterable: true,
                dataBound: onDataBound,
                sortable: true,
                pageable: true,
                columns: [{
                    field: "OrderID",
                    filterable: false
                },
                            "Freight",
                            {
                                field: "OrderDate",
                                title: "Order Date",
                                width: 120,
                                format: "{0:MM/dd/yyyy}"
                            }, {
                                field: "ShipName",
                                title: "Ship Name",
                                width: 260
                            }, {
                                field: "ShipCity",
                                title: "Ship City",
                                width: 150
                            }
                        ]
            });
        });
    </script>
</head>
<body>
    <div id="grid">
    </div>
</body>
</html>

I have implemented same thing with different way.

Iterate through a C++ Vector using a 'for' loop

If you use

std::vector<std::reference_wrapper<std::string>> names{ };

Do not forget, when you use auto in the for loop, to use also get, like this:

for (auto element in : names)
{
    element.get()//do something
}

git stash changes apply to new branch?

Is the standard procedure not working?

  • make changes
  • git stash save
  • git branch xxx HEAD
  • git checkout xxx
  • git stash pop

Shorter:

  • make changes
  • git stash
  • git checkout -b xxx
  • git stash pop

java calling a method from another class

You have to initialise the object (create the object itself) in order to be able to call its methods otherwise you would get a NullPointerException.

WordList words = new WordList();

Peak detection in a 2D array

There are several and extensive pieces of software available from the astronomy and cosmology community - this is a significant area of research both historically and currently.

Do not be alarmed if you are not an astronomer - some are easy to use outside the field. For example, you could use astropy/photutils:

https://photutils.readthedocs.io/en/stable/detection.html#local-peak-detection

[It seems a bit rude to repeat their short sample code here.]

An incomplete and slightly biased list of techniques/packages/links that might be of interest is given below - do add more in the comments and I will update this answer as necessary. Of course there is a trade-off of accuracy vs compute resources. [Honestly, there are too many to give code examples in a single answer such as this so I am not sure whether this answer will fly or not.]

Source Extractor https://www.astromatic.net/software/sextractor

MultiNest https://github.com/farhanferoz/MultiNest [+ pyMultiNest]

ASKAP/EMU source-finding challenge: https://arxiv.org/abs/1509.03931

You could also search for Planck and/or WMAP source-extraction challenges.

...

How to uninstall a windows service and delete its files without rebooting

Both Jonathan and Charles are right... you've got to stop the service first, then uninstall/reinstall. Combining their two answers makes the perfect batch file or PowerShell script.

I will make mention of a caution learned the hard way -- Windows 2000 Server (possibly the client OS as well) will require a reboot before the reinstall no matter what. There must be a registry key that is not fully cleared until the box is rebooted. Windows Server 2003, Windows XP and later OS versions do not suffer that pain.

Run Stored Procedure in SQL Developer?

To run procedure from SQL developer-only execute following command

EXECUTE PROCEDURE_NAME;

How to align texts inside of an input?

Without CSS: Use the STYLE property of text input

STYLE="text-align: right;"

How to get the current user in ASP.NET MVC

If you need to get the user from within the controller, use the User property of Controller. If you need it from the view, I would populate what you specifically need in the ViewData, or you could just call User as I think it's a property of ViewPage.

Turning multi-line string into single comma-separated

A solution written in pure Bash:

#!/bin/bash

sometext="something1:    +12.0   (some unnecessary trailing data (this must go))
something2:    +15.5   (some more unnecessary trailing data)
something4:    +9.0   (some other unnecessary data)
something1:    +13.5  (blah blah blah)"

a=()
while read -r a1 a2 a3; do
    # we can add some code here to check valid values or modify them
    a+=("${a2}")
done <<< "${sometext}"
# between parenthesis to modify IFS for the current statement only
(IFS=',' ; printf '%s: %s\n' "Result" "${a[*]}")

Result: +12.0,+15.5,+9.0,+13.5

What is the difference between URL parameters and query strings?

Parameters are key-value pairs that can appear inside URL path, and start with a semicolon character (;).

Query string appears after the path (if any) and starts with a question mark character (?).

Both parameters and query string contain key-value pairs.

In a GET request, parameters appear in the URL itself:

<scheme>://<username>:<password>@<host>:<port>/<path>;<parameters>?<query>#<fragment>

In a POST request, parameters can appear in the URL itself, but also in the datastream (as known as content).

Query string is always a part of the URL.

Parameters can be buried in form-data datastream when using POST method so they may not appear in the URL. Yes a POST request can define parameters as form data and in the URL, and this is not inconsistent because parameters can have several values.

I've found no explaination for this behavior so far. I guess it might be useful sometimes to "unhide" parameters from a POST request, or even let the code handling a GET request share some parts with the code handling a POST. Of course this can work only with server code supporting parameters in a URL.

Until you get better insights, I suggest you to use parameters only in form-data datastream of POST requests.

Sources:

What Every Developer Should Know About URLs

RFC 3986

How to make a vertical line in HTML

For an inline style I used this code:

<div style="border-left:1px black solid; position:absolute; left:50%; height:300px;" />

and that positioned it directly in the center.

Constants in Kotlin -- what's a recommended way to create them?

You don't need a class, an object or a companion object for declaring constants in Kotlin. You can just declare a file holding all the constants (for example Constants.kt or you can also put them inside any existing Kotlin file) and directly declare the constants inside the file. The constants known at compile time must be marked with const.

So, in this case, it should be:

const val MY_CONST = "something"

and then you can import the constant using:

import package_name.MY_CONST

You can refer to this link

Get the first element of an array

PHP 5.4+:

array_values($array)[0];

How to undo a git pull?

git reflog show should show you the history of HEAD. You can use that to figure out where you were before the pull. Then you can reset your HEAD to that commit.

MySQL Fire Trigger for both Insert and Update

unfortunately we can't use in MySQL after INSERT or UPDATE description, like in Oracle

Separation of business logic and data access in django

First of all, Don't repeat yourself.

Then, please be careful not to overengineer, sometimes it is just a waste of time, and makes someone lose focus on what is important. Review the zen of python from time to time.

Take a look at active projects

  • more people = more need to organize properly
  • the django repository they have a straightforward structure.
  • the pip repository they have a straigtforward directory structure.
  • the fabric repository is also a good one to look at.

    • you can place all your models under yourapp/models/logicalgroup.py
  • e.g User, Group and related models can go under yourapp/models/users.py
  • e.g Poll, Question, Answer ... could go under yourapp/models/polls.py
  • load what you need in __all__ inside of yourapp/models/__init__.py

More about MVC

  • model is your data
    • this includes your actual data
    • this also includes your session / cookie / cache / fs / index data
  • user interacts with controller to manipulate the model
    • this could be an API, or a view that saves/updates your data
    • this can be tuned with request.GET / request.POST ...etc
    • think paging or filtering too.
  • the data updates the view
    • the templates take the data and format it accordingly
    • APIs even w/o templates are part of the view; e.g. tastypie or piston
    • this should also account for the middleware.

Take advantage of middleware / templatetags

  • If you need some work to be done for each request, middleware is one way to go.
    • e.g. adding timestamps
    • e.g. updating metrics about page hits
    • e.g. populating a cache
  • If you have snippets of code that always reoccur for formatting objects, templatetags are good.
    • e.g. active tab / url breadcrumbs

Take advantage of model managers

  • creating User can go in a UserManager(models.Manager).
  • gory details for instances should go on the models.Model.
  • gory details for queryset could go in a models.Manager.
  • you might want to create a User one at a time, so you may think that it should live on the model itself, but when creating the object, you probably don't have all the details:

Example:

class UserManager(models.Manager):
   def create_user(self, username, ...):
      # plain create
   def create_superuser(self, username, ...):
      # may set is_superuser field.
   def activate(self, username):
      # may use save() and send_mail()
   def activate_in_bulk(self, queryset):
      # may use queryset.update() instead of save()
      # may use send_mass_mail() instead of send_mail()

Make use of forms where possible

A lot of boilerplate code can be eliminated if you have forms that map to a model. The ModelForm documentation is pretty good. Separating code for forms from model code can be good if you have a lot of customization (or sometimes avoid cyclic import errors for more advanced uses).

Use management commands when possible

  • e.g. yourapp/management/commands/createsuperuser.py
  • e.g. yourapp/management/commands/activateinbulk.py

if you have business logic, you can separate it out

  • django.contrib.auth uses backends, just like db has a backend...etc.
  • add a setting for your business logic (e.g. AUTHENTICATION_BACKENDS)
  • you could use django.contrib.auth.backends.RemoteUserBackend
  • you could use yourapp.backends.remote_api.RemoteUserBackend
  • you could use yourapp.backends.memcached.RemoteUserBackend
  • delegate the difficult business logic to the backend
  • make sure to set the expectation right on the input/output.
  • changing business logic is as simple as changing a setting :)

backend example:

class User(db.Models):
    def get_present_name(self): 
        # property became not deterministic in terms of database
        # data is taken from another service by api
        return remote_api.request_user_name(self.uid) or 'Anonymous' 

could become:

class User(db.Models):
   def get_present_name(self):
      for backend in get_backends():
         try:
            return backend.get_present_name(self)
         except: # make pylint happy.
            pass
      return None

more about design patterns

more about interface boundaries

  • Is the code you want to use really part of the models? -> yourapp.models
  • Is the code part of business logic? -> yourapp.vendor
  • Is the code part of generic tools / libs? -> yourapp.libs
  • Is the code part of business logic libs? -> yourapp.libs.vendor or yourapp.vendor.libs
  • Here is a good one: can you test your code independently?
    • yes, good :)
    • no, you may have an interface problem
    • when there is clear separation, unittest should be a breeze with the use of mocking
  • Is the separation logical?
    • yes, good :)
    • no, you may have trouble testing those logical concepts separately.
  • Do you think you will need to refactor when you get 10x more code?
    • yes, no good, no bueno, refactor could be a lot of work
    • no, that's just awesome!

In short, you could have

  • yourapp/core/backends.py
  • yourapp/core/models/__init__.py
  • yourapp/core/models/users.py
  • yourapp/core/models/questions.py
  • yourapp/core/backends.py
  • yourapp/core/forms.py
  • yourapp/core/handlers.py
  • yourapp/core/management/commands/__init__.py
  • yourapp/core/management/commands/closepolls.py
  • yourapp/core/management/commands/removeduplicates.py
  • yourapp/core/middleware.py
  • yourapp/core/signals.py
  • yourapp/core/templatetags/__init__.py
  • yourapp/core/templatetags/polls_extras.py
  • yourapp/core/views/__init__.py
  • yourapp/core/views/users.py
  • yourapp/core/views/questions.py
  • yourapp/core/signals.py
  • yourapp/lib/utils.py
  • yourapp/lib/textanalysis.py
  • yourapp/lib/ratings.py
  • yourapp/vendor/backends.py
  • yourapp/vendor/morebusinesslogic.py
  • yourapp/vendor/handlers.py
  • yourapp/vendor/middleware.py
  • yourapp/vendor/signals.py
  • yourapp/tests/test_polls.py
  • yourapp/tests/test_questions.py
  • yourapp/tests/test_duplicates.py
  • yourapp/tests/test_ratings.py

or anything else that helps you; finding the interfaces you need and the boundaries will help you.

Get login username in java

The 'set Username="Username" ' is a temporary override that only exists as long as the cmd windows is still up, once it is killed off, the variable loses value. So i think the

System.getProperty("user.name");

is still a short and precise code to use.

What is this date format? 2011-08-12T20:17:46.384Z

You can use the following example.

    String date = "2011-08-12T20:17:46.384Z";

    String inputPattern = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";

    String outputPattern = "yyyy-MM-dd HH:mm:ss";

    LocalDateTime inputDate = null;
    String outputDate = null;


    DateTimeFormatter inputFormatter = DateTimeFormatter.ofPattern(inputPattern, Locale.ENGLISH);
    DateTimeFormatter outputFormatter = DateTimeFormatter.ofPattern(outputPattern, Locale.ENGLISH);

    inputDate = LocalDateTime.parse(date, inputFormatter);
    outputDate = outputFormatter.format(inputDate);

    System.out.println("inputDate: " + inputDate);
    System.out.println("outputDate: " + outputDate);

Escape sequence \f - form feed - what exactly is it?

It comes from the era of Line Printers and green-striped fan-fold paper.

Trust me, you ain't gonna need it...

Serializing class instance to JSON

You could use jsonic for to serialize pretty much anything to JSON:

https://github.com/OrrBin/Jsonic

Example:

class TestClass:
def __init__(self):
    self.x = 1
    self.y = 2

instance = TestClass()
s = serialize(instance): # instance s set to: {"x":1, "y":2}
d = deserialize(s) # d is a new class instance of TestClass

pythonic has some nice features like declaring class attributes transient and type safe deserialization.

(A few years late with the answer, but i think it might help others)

Multiple returns from a function

You can get the values of two or more variables by setting them by reference:

function t(&$a, &$b) {
    $a = 1;
    $b = 2;
}


t($a, $b);

echo $a . '  ' . $b;

Output:

1 2

HTML5 textarea placeholder not appearing

use <textarea></textarea> instead of leaving a space between the opening and closing tags as <textarea> </textarea>

Plain Old CLR Object vs Data Transfer Object

A POCO follows the rules of OOP. It should (but doesn't have to) have state and behavior. POCO comes from POJO, coined by Martin Fowler [anecdote here]. He used the term POJO as a way to make it more sexy to reject the framework heavy EJB implementations. POCO should be used in the same context in .Net. Don't let frameworks dictate your object's design.

A DTO's only purpose is to transfer state, and should have no behavior. See Martin Fowler's explanation of a DTO for an example of the use of this pattern.

Here's the difference: POCO describes an approach to programming (good old fashioned object oriented programming), where DTO is a pattern that is used to "transfer data" using objects.

While you can treat POCOs like DTOs, you run the risk of creating an anemic domain model if you do so. Additionally, there's a mismatch in structure, since DTOs should be designed to transfer data, not to represent the true structure of the business domain. The result of this is that DTOs tend to be more flat than your actual domain.

In a domain of any reasonable complexity, you're almost always better off creating separate domain POCOs and translating them to DTOs. DDD (domain driven design) defines the anti-corruption layer (another link here, but best thing to do is buy the book), which is a good structure that makes the segregation clear.

JPG vs. JPEG image formats

There's no difference between the file extensions, and they are used interchangeably. I guess the 3-letter version stems from the DOS era...

However, there are different "flavors" of JPEG files. Most notably the JFIF standard and the EXIF standard. Most often these just use .jpg or .jpeg as file extensions, JFIF sometimes uses .jif or .jfif.

How can I access iframe elements with Javascript?

Using jQuery you can use contents(). For example:

var inside = $('#one').contents();

Why not use tables for layout in HTML?

Because it's HELL to maintain a site that uses tables, and takes a LOT longer to code. If you're scared of floating divs, go take a course in them. They're not difficult to understand and they're approximately 100 times more efficient and a million times less a pain in the ass (unless you don't understand them -- but hey, welcome to the world of computers).

Anyone considering doing their layout with a table better not expect me to maintain it. It's the most ass-backwards way to render a website. Thank god we have a much better alternative now. I would NEVER go back.

It's scary that some folks might not be aware of the time and energy benefits from creating a site using modern tools.

Get JSON object from URL

my solution only works for the next cases: if you are mistaking a multidimensaional array into a single one

$json = file_get_contents('url_json'); //get the json
$objhigher=json_decode($json); //converts to an object
$objlower = $objhigher[0]; // if the json response its multidimensional this lowers it
echo "<pre>"; //box for code
print_r($objlower); //prints the object with all key and values
echo $objlower->access_token; //prints the variable

i know that the answer was has already been answered but for those who came here looking for something i hope this can help you

How to ensure a <select> form field is submitted when it is disabled?

I found a workable solution: remove all the elements except the selected one. You can then change the style to something that looks disabled as well. Using jQuery:

jQuery(function($) {
    $('form').submit(function(){
        $('select option:not(:selected)', this).remove();
    });
});

Executing Javascript from Python

You can use js2py context to execute your js code and get output from document.write with mock document object:

import js2py

js = """
var output;
document = {
    write: function(value){
        output = value;
    }
}
""" + your_script

context = js2py.EvalJs()
context.execute(js)
print(context.output)

how does int main() and void main() work

If you really want to understand ANSI C 89, I need to correct you in one thing; In ANSI C 89 the difference between the following functions:

int main()
int main(void)
int main(int argc, char* argv[])

is:

int main()

  • a function that expects unknown number of arguments of unknown types. Returns an integer representing the application software status.

int main(void)

  • a function that expects no arguments. Returns an integer representing the application software status.

int main(int argc, char * argv[])

  • a function that expects argc number of arguments and argv[] arguments. Returns an integer representing the application software status.

About when using each of the functions

int main(void)

  • you need to use this function when your program needs no initial parameters to run/ load (parameters received from the OS - out of the program it self).

int main(int argc, char * argv[])

  • you need to use this function when your program needs initial parameters to load (parameters received from the OS - out of the program it self).

About void main()

In ANSI C 89, when using void main and compiling the project AS -ansi -pedantic (in Ubuntu, e.g) you will receive a warning indicating that your main function is of type void and not of type int, but you will be able to run the project. Most C developers tend to use int main() on all of its variants, though void main() will also compile.

How can I disable an <option> in a <select> based on its value in JavaScript?

For some reason other answers are unnecessarily complex, it's easy to do it in one line in pure JavaScript:

Array.prototype.find.call(selectElement.options, o => o.value === optionValue).disabled = true;

or

selectElement.querySelector('option[value="'+optionValue.replace(/["\\]/g, '\\$&')+'"]').disabled = true;

The performance depends on the number of the options (the more the options, the slower the first one) and whether you can omit the escaping (the replace call) from the second one. Also the first one uses Array.find and arrow functions that are not available in IE11.

JVM heap parameters

Apart from standard Heap parameters -Xms and -Xmx it's also good to know -XX:PermSize and -XX:MaxPermSize, which is used to specify size of Perm Gen space because even though you could have space in other generation in heap you can run out of memory if your perm gen space gets full. This link also has nice overview of some important JVM parameters.

Styling an anchor tag to look like a submit button

I Suggest you to use both Input Submit / Button instead of anchor and put this line of code onClick="javascript:location.href = 'http://stackoverflow.com';" in that Input Submit / Button which you want to work as link.

Submit Example

<input type="submit" value="Submit" onClick="javascript:location.href = 'some_url';" />

Button Example

<button type="button" onClick="javascript:location.href = 'some_url';" />Submit</button>

Short IF - ELSE statement

The ternary operator can only be the right side of an assignment and not a statement of its own.

http://www.devdaily.com/java/edu/pj/pj010018/

What is the best way to access redux store outside a react component?

export my store variable

export const store = createStore(rootReducer, applyMiddleware(ReduxThunk));

in action file or your file need them import this (store)

import {store} from "./path...";

this step get sate from store variable with function

const state = store.getState();

and get all of state your app

Implement a simple factory pattern with Spring 3 annotations

Based on solution by Pavel Cerný here we can make an universal typed implementation of this pattern. To to it, we need to introduce NamedService interface:

    public interface NamedService {
       String name();
    }

and add abstract class:

public abstract class AbstractFactory<T extends NamedService> {

    private final Map<String, T> map;

    protected AbstractFactory(List<T> list) {
        this.map = list
                .stream()
                .collect(Collectors.toMap(NamedService::name, Function.identity()));
    }

    /**
     * Factory method for getting an appropriate implementation of a service
     * @param name name of service impl.
     * @return concrete service impl.

     */
    public T getInstance(@NonNull final String name) {
        T t = map.get(name);
        if(t == null)
            throw new RuntimeException("Unknown service name: " + name);
        return t;
    }
}

Then we create a concrete factory of specific objects like MyService:

 public interface MyService extends NamedService {
           String name();
           void doJob();
 }

@Component
public class MyServiceFactory extends AbstractFactory<MyService> {

    @Autowired
    protected MyServiceFactory(List<MyService> list) {
        super(list);
    }
}

where List the list of implementations of MyService interface at compile time.

This approach works fine if you have multiple similar factories across app that produce objects by name (if producing objects by a name suffice you business logic of course). Here map works good with String as a key, and holds all the existing implementations of your services.

if you have different logic for producing objects, this additional logic can be moved to some another place and work in combination with these factories (that get objects by name).

Error: request entity too large

I faced the same issue recently and bellow solution workes for me.

Dependency : 
express >> version : 4.17.1
body-parser >> version": 1.19.0
const express = require('express');
const bodyParser = require('body-parser');

const app = express(); 
app.use(bodyParser.json({limit: '50mb'}));
app.use(bodyParser.urlencoded({limit: '50mb', extended: true}));

For understanding : HTTP 431

The HTTP 413 Payload Too Large response status code indicates that the request entity is larger than limits defined by server; the server might close the connection or return a Retry-After header field.

How to cast an object in Objective-C

Remember, Objective-C is a superset of C, so typecasting works as it does in C:

myEditController = [[SelectionListViewController alloc] init];
((SelectionListViewController *)myEditController).list = listOfItems;

Using Python Requests: Sessions, Cookies, and POST

I don't know how stubhub's api works, but generally it should look like this:

s = requests.Session()
data = {"login":"my_login", "password":"my_password"}
url = "http://example.net/login"
r = s.post(url, data=data)

Now your session contains cookies provided by login form. To access cookies of this session simply use

s.cookies

Any further actions like another requests will have this cookie

mysqli_fetch_array while loop columns

This one was your solution.

$x = 0;
while($row = mysqli_fetch_array($result)) {             
    $posts[$x]['post_id'] = $row['post_id'];
    $posts[$x]['post_title'] = $row['post_title'];
    $posts[$x]['type'] = $row['type'];
    $posts[$x]['author'] = $row['author'];
    $x++;
}

How to disable the ability to select in a DataGridView?

If you don't need to use the information in the selected cell then clearing selection works but if you need to still use the information in the selected cell you can do this to make it appear there is no selection and the back color will still be visible.

private void dataGridView_SelectionChanged(object sender, EventArgs e)
    {
        foreach (DataGridViewRow row in dataGridView.SelectedRows)
        {
            dataGridView.RowsDefaultCellStyle.SelectionBackColor = row.DefaultCellStyle.BackColor;
        }
    }

Compiling Java 7 code via Maven

try using a newer version of the maven compiler plugin:

    <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.2</version>
        <configuration>
            <source>1.7</source>
            <target>1.7</target>
        </configuration>
    </plugin>

also, specifying source file encoding in maven is better done globally:

<properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

EDIT: As this answer is still getting attention i'd just like to point out that the latest values (as of latest edit) are 3.2 for maven compiler plugin and 1.8 for java, as questions about compiling java 8 code via maven are bound to appear soon :-)

How to randomly select an item from a list?

You could just:

from random import randint

foo = ["a", "b", "c", "d", "e"]

print(foo[randint(0,4)])

How to reduce the space between <p> tags?

Setting both margin-bottom and margin-top to 0em will remove a space between paragraphs:

<style type="text/css">
p {margin-bottom: 0em; margin-top: 0em;}
</style>

How to select the first row for each group in MySQL?

I have not seen the following solution among the answers, so I thought I'd put it out there.

The problem is to select rows which are the first rows when ordered by AnotherColumn in all groups grouped by SomeColumn.

The following solution will do this in MySQL. id has to be a unique column which must not hold values containing - (which I use as a separator).

select t1.*
from mytable t1
inner join (
  select SUBSTRING_INDEX(
    GROUP_CONCAT(t3.id ORDER BY t3.AnotherColumn DESC SEPARATOR '-'),
    '-', 
    1
  ) as id
  from mytable t3
  group by t3.SomeColumn
) t2 on t2.id = t1.id


-- Where 
SUBSTRING_INDEX(GROUP_CONCAT(id order by AnotherColumn desc separator '-'), '-', 1)
-- can be seen as:
FIRST(id order by AnotherColumn desc)

-- For completeness sake:
SUBSTRING_INDEX(GROUP_CONCAT(id order by AnotherColumn desc separator '-'), '-', -1)
-- would then be seen as:
LAST(id order by AnotherColumn desc)

There is a feature request for FIRST() and LAST() in the MySQL bug tracker, but it was closed many years back.

How do I read configuration settings from Symfony2 config.yml?

Like it was saying previously - you can access any parameters by using injection container and use its parameter property.

"Symfony - Working with Container Service Definitions" is a good article about it.

A method to count occurrences in a list

You can do something like this to count from a list of things.

IList<String> names = new List<string>() { "ToString", "Format" };
IEnumerable<String> methodNames = typeof(String).GetMethods().Select(x => x.Name);

int count = methodNames.Where(x => names.Contains(x)).Count();

To count a single element

string occur = "Test1";
IList<String> words = new List<string>() {"Test1","Test2","Test3","Test1"};

int count = words.Where(x => x.Equals(occur)).Count();

Check last modified date of file in C#

Be aware that the function File.GetLastWriteTime does not always work as expected, the values are sometimes not instantaneously updated by the OS. You may get an old Timestamp, even if the file has been modified right before.

The behaviour may vary between OS versions. For example, this unit test worked well every time on my developer machine, but it always fails on our build server.

  [TestMethod]
  public void TestLastModifiedTimeStamps()
  {
     var tempFile = Path.GetTempFileName();
     var lastModified = File.GetLastWriteTime(tempFile);
     using (new FileStream(tempFile, FileMode.Create, FileAccess.Write, FileShare.None))
     {

     }
     Assert.AreNotEqual(lastModified, File.GetLastWriteTime(tempFile));
  }

See File.GetLastWriteTime seems to be returning 'out of date' value

Your options:

a) live with the occasional omissions.

b) Build up an active component realising the observer pattern (eg. a tcp server client structure), communicating the changes directly instead of writing / reading files. Fast and flexible, but another dependency and a possible point of failure (and some work, of course).

c) Ensure the signalling process by replacing the content of a dedicated signal file that other processes regularly read. It´s not that smart as it´s a polling procedure and has a greater overhead than calling File.GetLastWriteTime, but if not checking the content from too many places too often, it will do the work.

/// <summary>
/// type to set signals or check for them using a central file 
/// </summary>
public class FileSignal
{
    /// <summary>
    /// path to the central file for signal control
    /// </summary>
    public string FilePath { get; private set; }

    /// <summary>
    /// numbers of retries when not able to retrieve (exclusive) file access
    /// </summary>
    public int MaxCollisions { get; private set; }

    /// <summary>
    /// timespan to wait until next try
    /// </summary>
    public TimeSpan SleepOnCollisionInterval { get; private set; }

    /// <summary>
    /// Timestamp of the last signal
    /// </summary>
    public DateTime LastSignal { get; private set; }

    /// <summary>
    /// constructor
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>
    /// <param name="maxCollisions">numbers of retries when not able to retrieve (exclusive) file access</param>
    /// <param name="sleepOnCollisionInterval">timespan to wait until next try </param>
    public FileSignal(string filePath, int maxCollisions, TimeSpan sleepOnCollisionInterval)
    {
        FilePath = filePath;
        MaxCollisions = maxCollisions;
        SleepOnCollisionInterval = sleepOnCollisionInterval;
        LastSignal = GetSignalTimeStamp();
    }

    /// <summary>
    /// constructor using a default value of 50 ms for sleepOnCollisionInterval
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>
    /// <param name="maxCollisions">numbers of retries when not able to retrieve (exclusive) file access</param>        
    public FileSignal(string filePath, int maxCollisions): this (filePath, maxCollisions, TimeSpan.FromMilliseconds(50))
    {
    }

    /// <summary>
    /// constructor using a default value of 50 ms for sleepOnCollisionInterval and a default value of 10 for maxCollisions
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>        
    public FileSignal(string filePath) : this(filePath, 10)
    {
    }

    private Stream GetFileStream(FileAccess fileAccess)
    {
        var i = 0;
        while (true)
        {
            try
            {
                return new FileStream(FilePath, FileMode.Create, fileAccess, FileShare.None);
            }
            catch (Exception e)
            {
                i++;
                if (i >= MaxCollisions)
                {
                    throw e;
                }
                Thread.Sleep(SleepOnCollisionInterval);
            };
        };
    }

    private DateTime GetSignalTimeStamp()
    {
        if (!File.Exists(FilePath))
        {
            return DateTime.MinValue;
        }
        using (var stream = new FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.None))
        {
            if(stream.Length == 0)
            {
                return DateTime.MinValue;
            }
            using (var reader = new BinaryReader(stream))
            {
                return DateTime.FromBinary(reader.ReadInt64());
            };                
        }
    }

    /// <summary>
    /// overwrites the existing central file and writes the current time into it.
    /// </summary>
    public void Signal()
    {
        LastSignal = DateTime.Now;
        using (var stream = new FileStream(FilePath, FileMode.Create, FileAccess.Write, FileShare.None))
        {
            using (var writer = new BinaryWriter(stream))
            {
                writer.Write(LastSignal.ToBinary());
            }
        }
    }

    /// <summary>
    /// returns true if the file signal has changed, otherwise false.
    /// </summary>        
    public bool CheckIfSignalled()
    {
        var signal = GetSignalTimeStamp();
        var signalTimestampChanged = LastSignal != signal;
        LastSignal = signal;
        return signalTimestampChanged;
    }
}

Some tests for it:

    [TestMethod]
    public void TestSignal()
    {
        var fileSignal = new FileSignal(Path.GetTempFileName());
        var fileSignal2 = new FileSignal(fileSignal.FilePath);
        Assert.IsFalse(fileSignal.CheckIfSignalled());
        Assert.IsFalse(fileSignal2.CheckIfSignalled());
        Assert.AreEqual(fileSignal.LastSignal, fileSignal2.LastSignal);
        fileSignal.Signal();
        Assert.IsFalse(fileSignal.CheckIfSignalled());
        Assert.AreNotEqual(fileSignal.LastSignal, fileSignal2.LastSignal);
        Assert.IsTrue(fileSignal2.CheckIfSignalled());
        Assert.AreEqual(fileSignal.LastSignal, fileSignal2.LastSignal);
        Assert.IsFalse(fileSignal2.CheckIfSignalled());
    }

How to dynamically set bootstrap-datepicker's date value?

This works for me

$(".datepicker").datepicker("update", new Date());

How to set custom ActionBar color / style?

For Android 3.0 and higher only

When supporting Android 3.0 and higher only, you can define the action bar's background like this:

res/values/themes.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- the theme applied to the application or activity -->
    <style name="CustomActionBarTheme" parent="@style/Theme.Holo.Light.DarkActionBar">
       <item name="android:actionBarStyle">@style/MyActionBar</item>
    </style>

<!-- ActionBar styles -->
  <style name="MyActionBar" parent="@style/Widget.Holo.Light.ActionBar.Solid.Inverse">
       <item name="android:background">#ff0000</item>
  </style>
</resources>

For Android 2.1 and higher

When using the Support Library, your style XML file might look like this:

<?xml version="1.0" encoding="utf-8"?>
  <resources>
  <!-- the theme applied to the application or activity -->
 <style name="CustomActionBarTheme" parent="@style/Theme.AppCompat.Light.DarkActionBar">
    <item name="android:actionBarStyle">@style/MyActionBar</item>

    <!-- Support library compatibility -->
    <item name="actionBarStyle">@style/MyActionBar</item>
</style>

<!-- ActionBar styles -->
<style name="MyActionBar"
       parent="@style/Widget.AppCompat.Light.ActionBar.Solid.Inverse">
    <item name="android:background">@drawable/actionbar_background</item>

    <!-- Support library compatibility -->
    <item name="background">@drawable/actionbar_background</item>
  </style>
 </resources>

Then apply your theme to your entire app or individual activities:

for more details Documentaion

How do I open phone settings when a button is clicked?

Using @vivek's hint I develop an utils class based on Swift 3, hope you appreciate!

import Foundation
import UIKit

public enum PreferenceType: String {

    case about = "General&path=About"
    case accessibility = "General&path=ACCESSIBILITY"
    case airplaneMode = "AIRPLANE_MODE"
    case autolock = "General&path=AUTOLOCK"
    case cellularUsage = "General&path=USAGE/CELLULAR_USAGE"
    case brightness = "Brightness"
    case bluetooth = "Bluetooth"
    case dateAndTime = "General&path=DATE_AND_TIME"
    case facetime = "FACETIME"
    case general = "General"
    case keyboard = "General&path=Keyboard"
    case castle = "CASTLE"
    case storageAndBackup = "CASTLE&path=STORAGE_AND_BACKUP"
    case international = "General&path=INTERNATIONAL"
    case locationServices = "LOCATION_SERVICES"
    case accountSettings = "ACCOUNT_SETTINGS"
    case music = "MUSIC"
    case equalizer = "MUSIC&path=EQ"
    case volumeLimit = "MUSIC&path=VolumeLimit"
    case network = "General&path=Network"
    case nikePlusIPod = "NIKE_PLUS_IPOD"
    case notes = "NOTES"
    case notificationsId = "NOTIFICATIONS_ID"
    case phone = "Phone"
    case photos = "Photos"
    case managedConfigurationList = "General&path=ManagedConfigurationList"
    case reset = "General&path=Reset"
    case ringtone = "Sounds&path=Ringtone"
    case safari = "Safari"
    case assistant = "General&path=Assistant"
    case sounds = "Sounds"
    case softwareUpdateLink = "General&path=SOFTWARE_UPDATE_LINK"
    case store = "STORE"
    case twitter = "TWITTER"
    case facebook = "FACEBOOK"
    case usage = "General&path=USAGE"
    case video = "VIDEO"
    case vpn = "General&path=Network/VPN"
    case wallpaper = "Wallpaper"
    case wifi = "WIFI"
    case tethering = "INTERNET_TETHERING"
    case blocked = "Phone&path=Blocked"
    case doNotDisturb = "DO_NOT_DISTURB"

}

enum PreferenceExplorerError: Error {
    case notFound(String)
}

open class PreferencesExplorer {

    // MARK: - Class properties -

    static private let preferencePath = "App-Prefs:root"

    // MARK: - Class methods -

    static func open(_ preferenceType: PreferenceType) throws {
        let appPath = "\(PreferencesExplorer.preferencePath)=\(preferenceType.rawValue)"
        if let url = URL(string: appPath) {
            if #available(iOS 10.0, *) {
                UIApplication.shared.open(url, options: [:], completionHandler: nil)
            } else {
               UIApplication.shared.openURL(url)
            }
        } else {
            throw PreferenceExplorerError.notFound(appPath)
        }
    }

}

This is very helpful since that API's will change for sure and you can refactor once and very fast!

slf4j: how to log formatted message, object array, exception

In addition to @Ceki 's answer, If you are using logback and setup a config file in your project (usually logback.xml), you can define the log to plot the stack trace as well using

<encoder>
    <pattern>%date |%-5level| [%thread] [%file:%line] - %msg%n%ex{full}</pattern> 
</encoder>

the %ex in pattern is what makes the difference

How to refresh token with Google API client?

Sometimes Refresh Token i not generated by using $client->setAccessType ("offline");.

Try this:

$client->setAccessType ("offline");
$client->setApprovalPrompt ("force"); 

What is the best way to create a string array in python?

In Python, the tendency is usually that one would use a non-fixed size list (that is to say items can be appended/removed to it dynamically). If you followed this, there would be no need to allocate a fixed-size collection ahead of time and fill it in with empty values. Rather, as you get or create strings, you simply add them to the list. When it comes time to remove values, you simply remove the appropriate value from the string. I would imagine you can probably use this technique for this. For example (in Python 2.x syntax):

>>> temp_list = []
>>> print temp_list
[]
>>> 
>>> temp_list.append("one")
>>> temp_list.append("two")
>>> print temp_list
['one', 'two']
>>> 
>>> temp_list.append("three")
>>> print temp_list
['one', 'two', 'three']
>>> 

Of course, some situations might call for something more specific. In your case, a good idea may be to use a deque. Check out the post here: Python, forcing a list to a fixed size. With this, you can create a deque which has a fixed size. If a new value is appended to the end, the first element (head of the deque) is removed and the new item is appended onto the deque. This may work for what you need, but I don't believe this is considered the "norm" for Python.

Have a variable in images path in Sass?

No need for a function:

$assetPath : "/assets/images";

...

body {
  margin: 0 auto;
  background: url(#{$assetPath}/site/background.jpg) repeat-x fixed 0 0;
  width: 100%; }

See the interpolation docs for details.

Integrating the ZXing library directly into my Android application

I tried all possible ways to achieve this and then I discovered Minified version of xZing by JourneyApps. I have ported that for eclipse and shared on GitHub.

If you are using eclipse use this project:-

https://github.com/hiteshsahu/XZing-Barcode-Scanner-Minified-Eclipse

If you are using Studio use this project :-

https://github.com/journeyapps/zxing-android-embedded

Advantages

  1. Inbuilt Barcode scanner in your App do not required to install third party apps using playstore.

  2. You dont need to get confused between Core,Android client etc jars simply drop this packages and relevent layouts in your project and you are good to go. Only Jar required is com.google.zxing:core:3.2.0 which you can download from

    http://mvnrepository.com/artifact/com.google.zxing/core/3.2.0

  3. No need to add tons of packages see images below for comparison

Before :-

enter image description here

After :-

enter image description here

  1. Most important part is they are highly customizable ie. you can add flash light, use it in fragment and support orientation change.

  2. You can use this Capture activity in Cordova App for barcode scanneing.

your capture activity in app manifest would look like this

  <activity
            android:name="com.journeyapps.barcodescanner.CaptureActivity"
            android:clearTaskOnLaunch="true"
            android:configChanges="orientation|keyboardHidden"
            android:exported="false"
            android:screenOrientation="fullSensor"
            android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
            android:windowSoftInputMode="stateAlwaysHidden" >
            <intent-filter>
                <action android:name="com.google.zxing.client.android.SCAN" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

and plugin will look like this

public class BarcodeScanner extends CordovaPlugin {
    public static final int REQUEST_CODE = 0x0ba7c0de;

    private static final String SCAN = "scan";
    private static final String CANCELLED = "cancelled";
    private static final String FORMAT = "format";
    private static final String TEXT = "text";
    private static final String SCAN_INTENT = "com.google.zxing.client.android.SCAN";

    private static final String LOG_TAG = "BarcodeScanner";

    private CallbackContext callbackContext;

    /**
     * Constructor.
     */
    public BarcodeScanner() {


    }

    /**
     * Executes the request.
     *
     * This method is called from the WebView thread. To do a non-trivial amount of work, use:
     *     cordova.getThreadPool().execute(runnable);
     *
     * To run on the UI thread, use:
     *     cordova.getActivity().runOnUiThread(runnable);
     *
     * @param action          The action to execute.
     * @param args            The exec() arguments.
     * @param callbackContext The callback context used when calling back into JavaScript.
     * @return                Whether the action was valid.
     *
     * @sa https://github.com/apache/cordova-android/blob/master/framework/src/org/apache/cordova/CordovaPlugin.java
     */
    @Override
    public boolean execute(String action, JSONArray args, CallbackContext callbackContext) {
        this.callbackContext = callbackContext;
        if (action.equals(SCAN)) {
            scan(args);
        } else {
            return false;
        }
        return true;
    }

    /**
     * Starts an intent to scan and decode a barcode.
     */
    public void scan(JSONArray args) {
        Intent intentScan = new Intent(SCAN_INTENT);
        intentScan.addCategory(Intent.CATEGORY_DEFAULT);

        // add config as intent extras
        if(args.length() > 0) {

            JSONObject obj;
            JSONArray names;
            String key;
            Object value;

            for(int i=0; i<args.length(); i++) {

                try {
                    obj = args.getJSONObject(i);
                } catch(JSONException e) {
                    Log.i("CordovaLog", e.getLocalizedMessage());
                    continue;
                }

                names = obj.names();
                for(int j=0; j<names.length(); j++) {
                    try {
                        key = names.getString(j);
                        value = obj.get(key);

                        if(value instanceof Integer) {
                            intentScan.putExtra(key, (Integer)value);
                        } else if(value instanceof String) {
                            intentScan.putExtra(key, (String)value);
                        }

                    } catch(JSONException e) {
                        Log.i("CordovaLog", e.getLocalizedMessage());
                        continue;
                    }
                }
            }

        }

        // avoid calling other phonegap apps
        intentScan.setPackage(this.cordova.getActivity().getApplicationContext().getPackageName());

        this.cordova.startActivityForResult((CordovaPlugin) this, intentScan, REQUEST_CODE);
    }

    /**
     * Called when the barcode scanner intent completes.
     *
     * @param requestCode The request code originally supplied to startActivityForResult(),
     *                       allowing you to identify who this result came from.
     * @param resultCode  The integer result code returned by the child activity through its setResult().
     * @param intent      An Intent, which can return result data to the caller (various data can be attached to Intent "extras").
     */
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {
        if (requestCode == REQUEST_CODE) {
            if (resultCode == Activity.RESULT_OK) {
                JSONObject obj = new JSONObject();
                try {
                    obj.put(TEXT, intent.getStringExtra("SCAN_RESULT"));
                    obj.put(FORMAT, intent.getStringExtra("SCAN_RESULT_FORMAT"));
                    obj.put(CANCELLED, false);
                } catch (JSONException e) {
                    Log.d(LOG_TAG, "JSONException "+e.getMessage());
                }
                this.callbackContext.success(obj);
            } else if (resultCode == Activity.RESULT_CANCELED) {
                this.callbackContext.success("");
            } else {
                this.callbackContext.error("Technical Problem");
            }
        }
    }
}

Happy Integration !!

PostgreSQL: Modify OWNER on all tables simultaneously in PostgreSQL

For tables you must loop that:

for tbl in `psql -qAt -c "select tablename from pg_tables where schemaname = 'public';" YOUR_DB` ; do  psql -U postgres -c "alter table \"$tbl\" owner to NEW_USER" YOUR_DB ; done

How do I filter date range in DataTables?

Following one is working fine with moments js 2.10 and above

$.fn.dataTableExt.afnFiltering.push(
        function( settings, data, dataIndex ) {
            var min  = $('#min-date').val()
            var max  = $('#max-date').val()
            var createdAt = data[0] || 0; // Our date column in the table
            //createdAt=createdAt.split(" ");
            var startDate   = moment(min, "DD/MM/YYYY");
            var endDate     = moment(max, "DD/MM/YYYY");
            var diffDate = moment(createdAt, "DD/MM/YYYY");
            //console.log(startDate);
            if (
              (min == "" || max == "") ||
              (diffDate.isBetween(startDate, endDate))


            ) {  return true;  }
            return false;

        }
    );

Import Excel Spreadsheet Data to an EXISTING sql table?

If you would like a software tool to do this, you might like to check out this step-by-step guide:

"How to Validate and Import Excel spreadsheet to SQL Server database"

http://leansoftware.net/forum/en-us/help/excel-database-tasks/worked-examples/how-to-import-excel-spreadsheet-to-sql-server-data.aspx

How to take MySQL database backup using MySQL Workbench?

  1. On ‘HOME’ page -- > select 'Manage Import / Export' under 'Server Administration'

  2. A box comes up... choose which server holds the data you want to back up.

  3. On the 'Export to Disk' tab, then select which databases you want to export.

  4. If you want all the tables, select option ‘Export to self-contained file’, otherwise choose the other option for a selective restore

  5. If you need advanced options, see other post, otherwise then click ‘Start Export’

Should a retrieval method return 'null' or throw an exception when it can't produce the return value?

Don't think anyone mentioned the overhead in exception handling - takes additional resources to load up and process the exception so unless its a true app killing or process stopping event (going forward would cause more harm than good) I would opt for passing back a value the calling environment could interpret as it sees fit.

LEFT INNER JOIN vs. LEFT OUTER JOIN - Why does the OUTER take longer?

The fact that the same number of rows is returned is an after fact, the query optimizer cannot know in advance that every row in Accepts has a matching row in Marker, can it?

If you join two tables A and B, say A has 1 million rows and B has 1 row. If you say A LEFT INNER JOIN B it means only rows that match both A and B can result, so the query plan is free to scan B first, then use an index to do a range scan in A, and perhaps return 10 rows. But if you say A LEFT OUTER JOIN B then at least all rows in A have to be returned, so the plan must scan everything in A no matter what it finds in B. By using an OUTER join you are eliminating one possible optimization.

If you do know that every row in Accepts will have a match in Marker, then why not declare a foreign key to enforce this? The optimizer will see the constraint, and if is trusted, will take it into account in the plan.

How to convert .pfx file to keystore with private key?

Using JDK 1.6 or later

It has been pointed out by Justin in the comments below that keytool alone is capable of doing this using the following command (although only in JDK 1.6 and later):

keytool -importkeystore -srckeystore mypfxfile.pfx -srcstoretype pkcs12 
-destkeystore clientcert.jks -deststoretype JKS

Using JDK 1.5 or below

OpenSSL can do it all. This answer on JGuru is the best method that I've found so far.

Firstly make sure that you have OpenSSL installed. Many operating systems already have it installed as I found with Mac OS X.

The following two commands convert the pfx file to a format that can be opened as a Java PKCS12 key store:

openssl pkcs12 -in mypfxfile.pfx -out mypemfile.pem
openssl pkcs12 -export -in mypemfile.pem -out mykeystore.p12 -name "MyCert"

NOTE that the name provided in the second command is the alias of your key in the new key store.

You can verify the contents of the key store using the Java keytool utility with the following command:

keytool -v -list -keystore mykeystore.p12 -storetype pkcs12

Finally if you need to you can convert this to a JKS key store by importing the key store created above into a new key store:

keytool -importkeystore -srckeystore mykeystore.p12 -destkeystore clientcert.jks -srcstoretype pkcs12 -deststoretype JKS

How to get cumulative sum

Without using any type of JOIN cumulative salary for a person fetch by using follow query:

SELECT * , (
  SELECT SUM( salary ) 
  FROM  `abc` AS table1
  WHERE table1.ID <=  `abc`.ID
    AND table1.name =  `abc`.Name
) AS cum
FROM  `abc` 
ORDER BY Name

Is there an equivalent of lsusb for OS X

I got tired of forgetting the system_profiler SPUSBDataType syntax, so I made an lsusb alternative. You can find it here , or install it with homebrew:

brew install lsusb

Query for documents where array size is greater than 1

db.accommodations.find({"name":{"$exists":true, "$ne":[], "$not":{"$size":1}}})

JS: Uncaught TypeError: object is not a function (onclick)

Please change only the name of the function; no other change is required

<script>
    function totalbandwidthresult() {
        alert("fdf");
        var fps = Number(document.calculator.fps.value);
        var bitrate = Number(document.calculator.bitrate.value);
        var numberofcameras = Number(document.calculator.numberofcameras.value);
        var encoding = document.calculator.encoding.value;
        if (encoding = "mjpeg") {
            storage = bitrate * fps;
        } else {
            storage = bitrate;
        }

        totalbandwidth = (numberofcameras * storage) / 1000;
        alert(totalbandwidth);
        document.calculator.totalbandwidthresult.value = totalbandwidth;
    }
</script>

<form name="calculator" class="formtable">
    <div class="formrow">
        <label for="rcname">RC Name</label>
        <input type="text" name="rcname">
    </div>
    <div class="formrow">
        <label for="fps">FPS</label>
        <input type="text" name="fps">
    </div>
    <div class="formrow">
        <label for="bitrate">Bitrate</label>
        <input type="text" name="bitrate">
    </div>
    <div class="formrow">
        <label for="numberofcameras">Number of Cameras</label>
        <input type="text" name="numberofcameras">
    </div>
    <div class="formrow">
        <label for="encoding">Encoding</label>
        <select name="encoding" id="encodingoptions">
            <option value="h264">H.264</option>
            <option value="mjpeg">MJPEG</option>
            <option value="mpeg4">MPEG4</option>
        </select>
    </div>Total Storage:
    <input type="text" name="totalstorage">Total Bandwidth:
    <input type="text" name="totalbandwidth">
    <input type="button" value="totalbandwidthresult" onclick="totalbandwidthresult();">
</form>

CSS hide scroll bar, but have element scrollable

I combined a couple of different answers in SO into the following snippet, which should work on all, if not most, modern browsers I believe. All you have to do is add the CSS class .disable-scrollbars onto the element you wish to apply this to.

.disable-scrollbars::-webkit-scrollbar {
    width: 0px;
    background: transparent; /* Chrome/Safari/Webkit */
}

.disable-scrollbars {
  scrollbar-width: none; /* Firefox */
  -ms-overflow-style: none;  /* IE 10+ */
}

And if you want to use SCSS/SASS:

.disable-scrollbars {
  scrollbar-width: none; /* Firefox */
  -ms-overflow-style: none;  /* IE 10+ */
  &::-webkit-scrollbar {
    width: 0px;
    background: transparent; /* Chrome/Safari/Webkit */
  }
}

How can I select all rows with sqlalchemy?

You can easily import your model and run this:

from models import User

# User is the name of table that has a column name
users = User.query.all()

for user in users:
    print user.name

How to pass an event object to a function in Javascript?

Although this is the accepted answer, toto_tico's answer below is better :)

Try making the onclick js use 'return' to ensure the desired return value gets used...

<button type="button" value="click me" onclick="return check_me();" />

Calling a stored procedure in Oracle with IN and OUT parameters

If you set the server output in ON mode before the entire code, it works, otherwise put_line() will not work. Try it!

The code is,

set serveroutput on;
CREATE OR REPLACE PROCEDURE PROC1(invoicenr IN NUMBER, amnt OUT NUMBER)
AS BEGIN
SELECT AMOUNT INTO amnt FROM INVOICE WHERE INVOICE_NR = invoicenr;
END;

And then call the function as it is:

DECLARE
amount NUMBER;
BEGIN
PROC1(1000001, amount);
dbms_output.put_line(amount);
END;

fatal error LNK1104: cannot open file 'kernel32.lib'

If the above solution doesn't work, check to see if you have $(LibraryPath) in Properties->VC++ Directories->Library Directories. If you are missing it, try adding it.

How to concat a string to xsl:value-of select="...?

The easiest way to concat a static text string to a selected value is to use element.

<a>
  <xsl:attribute name="href"> 
    <xsl:value-of select="/*/properties/property[@name='report']/@value" />
    <xsl:text>staticIconExample.png</xsl:text>
  </xsl:attribute>
</a>

Clicking a checkbox with ng-click does not update the model

The order in which ng-click and ng-model will be executed is ambiguous (since neither explicitly set their priority). The most stable solution to this would be to avoid using them on the same element.

Also, you probably do not want the behavior that the examples show; you want the checkbox to respond to clicks on the complete label text, not only the checkbox. Hence, the cleanest solution would be to wrap the input (with ng-model) inside a label (with ng-click):

<label ng-click="onCompleteTodo(todo)">
  <input type='checkbox' ng-model="todo.done">
  {{todo.text}}
</label>

Working example: http://jsfiddle.net/b3NLH/1/

How to remove a newline from a string in Bash

Clean your variable by removing all the carriage returns:

COMMAND=$(echo $COMMAND|tr -d '\n')

How to get the body's content of an iframe in Javascript?

To get body content from javascript ,i have tried the following code:

var frameObj = document.getElementById('id_description_iframe');

var frameContent = frameObj.contentWindow.document.body.innerHTML;

where "id_description_iframe" is your iframe's id. This code is working fine for me.

Git diff --name-only and copy that list

Here's a one-liner:

List changed files & pack them as *.zip:

git diff --name-only | zip patched.zip -@

List last committed changed files & pack them as *.zip:

git diff --name-only HEAD~ HEAD | zip patched.zip -@

jquery animate .css

You can actually still use ".css" and apply css transitions to the div being affected. So continue using ".css" and add the below styles to your stylesheet for "#hfont1". Since ".css" allows for a lot more properties than ".animate", this is always my preferred method.

#hfont1 {
    -webkit-transition: width 0.4s;
    transition: width 0.4s;
}

PHP post_max_size overrides upload_max_filesize

change in php.ini max_input_vars 1000

How to get the current date/time in Java

In Java 8 it is:

LocalDateTime.now()

and in case you need time zone info:

ZonedDateTime.now()

and in case you want to print fancy formatted string:

System.out.println(ZonedDateTime.now().format(DateTimeFormatter.RFC_1123_DATE_TIME))

JavaScript to get rows count of a HTML table

$('tableName').find('tr').length

Python assigning multiple variables to same value? list behavior

The code that does what I need could be this:

# test

aux=[[0 for n in range(3)] for i in range(4)]
print('aux:',aux)

# initialization

a,b,c,d=[[0 for n in range(3)] for i in range(4)]

# changing values

a[0]=1
d[2]=5
print('a:',a)
print('b:',b)
print('c:',c)
print('d:',d)

Result:

('aux:', [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]])
('a:', [1, 0, 0])
('b:', [0, 0, 0])
('c:', [0, 0, 0])
('d:', [0, 0, 5])

Changing background color of selected cell?

I have a highly customized UITableViewCell. So I implemented my own cell selection.

cell.selectionStyle = UITableViewCellSelectionStyleNone;

I created a method in my cell's class:

- (void)highlightCell:(BOOL)highlight
{
    if (highlight) {
        self.contentView.backgroundColor = RGB(0x355881);
        _bodyLabel.textColor = RGB(0xffffff);
        _fromLabel.textColor = RGB(0xffffff);
        _subjectLabel.textColor = RGB(0xffffff);
        _dateLabel.textColor = RGB(0xffffff);
    }
    else {
        self.contentView.backgroundColor = RGB(0xf7f7f7);;
        _bodyLabel.textColor = RGB(0xaaaaaa);
        _fromLabel.textColor = [UIColor blackColor];
        _subjectLabel.textColor = [UIColor blackColor];
        _dateLabel.textColor = RGB(0x496487);
    }
}

In my UITableViewController class in ViewWillAppear added this:

NSIndexPath *tableSelection = [self.tableView indexPathForSelectedRow];
SideSwipeTableViewCell *cell = (SideSwipeTableViewCell*)[self.tableView cellForRowAtIndexPath:tableSelection];
[cell highlightCell:NO];

In didSelectRow added this:

SideSwipeTableViewCell *cell = (SideSwipeTableViewCell*)[self.tableView cellForRowAtIndexPath:indexPath];
[cell highlightCell:YES];

Angularjs -> ng-click and ng-show to show a div

I implemented it something this way

Controller function:

app.controller("aboutController", function(){
this.selected = true;
this.toggle = function(){
  this.selected = this.selected?false:true;
}
});

HTML:

<div ng-controller="aboutController as about">
 <div ng-click="about.toggle()">Click Me to toggle the Fruits Name</div>
 <div ng-show ="about.selected">Apple is a delicious fruit</div>
</div>

How can I get a list of all functions stored in the database of a particular schema in PostgreSQL?

Run below SQL query to create a view which will show all functions:

CREATE OR REPLACE VIEW show_functions AS
    SELECT routine_name FROM information_schema.routines 
        WHERE routine_type='FUNCTION' AND specific_schema='public';

"No such file or directory" but it exists

This error may also occur if trying to run a script and the shebang is misspelled. Make sure it reads #!/bin/sh, #!/bin/bash, or whichever interpreter you're using.

How can I combine multiple rows into a comma-delimited list in Oracle?

I have always had to write some PL/SQL for this or I just concatenate a ',' to the field and copy into an editor and remove the CR from the list giving me the single line.

That is,

select country_name||', ' country from countries

A little bit long winded both ways.

If you look at Ask Tom you will see loads of possible solutions but they all revert to type declarations and/or PL/SQL

Ask Tom

How do I tell if an object is a Promise?

This is how graphql-js package detects promises:

function isPromise(value) {
  return Boolean(value && typeof value.then === 'function');
}

value is the returned value of your function. I'm using this code in my project and have no problem so far.

How to append rows in a pandas dataframe in a for loop?

There are 2 reasons you may append rows in a loop, 1. add to an existing df, and 2. create a new df.

to create a new df, I think its well documented that you should either create your data as a list and then create the data frame:

cols = ['c1', 'c2', 'c3']
lst = []
for a in range(2):
    lst.append([1, 2, 3])
df1 = pd.DataFrame(lst, columns=cols)
df1
Out[3]: 
   c1  c2  c3
0   1   2   3
1   1   2   3

OR, Create the dataframe with an index and then add to it

cols = ['c1', 'c2', 'c3']
df2 = pd.DataFrame(columns=cols, index=range(2))
for a in range(2):
    df2.loc[a].c1 = 4
    df2.loc[a].c2 = 5
    df2.loc[a].c3 = 6
df2
Out[4]: 
  c1 c2 c3
0  4  5  6
1  4  5  6

If you want to add to an existing dataframe, you could use either method above and then append the df's together (with or without the index):

df3 = df2.append(df1, ignore_index=True)
df3
Out[6]: 
  c1 c2 c3
0  4  5  6
1  4  5  6
2  1  2  3
3  1  2  3

Or, you can also create a list of dictionary entries and append those as in the answer above.

lst_dict = []
for a in range(2):
    lst_dict.append({'c1':2, 'c2':2, 'c3': 3})
df4 = df1.append(lst_dict)
df4
Out[7]: 
   c1  c2  c3
0   1   2   3
1   1   2   3
0   2   2   3
1   2   2   3

Using the dict(zip(cols, vals)))

lst_dict = []
for a in range(2):
    vals = [7, 8, 9]
    lst_dict.append(dict(zip(cols, vals)))
df5 = df1.append(lst_dict)

How to convert an image to base64 encoding?

You can also do this via curl, just you need a path to an image file and pass it to the function given below..

public static function getImageDataFromUrl($url)
{
    $urlParts = pathinfo($url);
    $extension = $urlParts['extension'];
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    $response = curl_exec($ch);
    curl_close($ch);
    $base64 = 'data:image/' . $extension . ';base64,' . base64_encode($response);
    return $base64;

}

How can I export Excel files using JavaScript?

To answer your question with a working example:

<script type="text/javascript">
function DownloadJSON2CSV(objArray)
{
    var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray;

    var str = '';

    for (var i = 0; i < array.length; i++) {
        var line = new Array();

        for (var index in array[i]) {
           line.push('"' + array[i][index] + '"');
        }

        str += line.join(';');
        str += '\r\n';
    }
    window.open( "data:text/csv;charset=utf-8," + encodeURIComponent(str));
}
</script>

Pandas: Return Hour from Datetime Column Directly

For posterity: as of 0.15.0, there is a handy .dt accessor you can use to pull such values from a datetime/period series (in the above case, just sales.timestamp.dt.hour!

Why am I getting ImportError: No module named pip ' right after installing pip?

Follow steps given in https://michlstechblog.info/blog/python-install-python-with-pip-on-windows-by-the-embeddable-zip-file/. Replace x with version number of Python.

  1. Open the pythonxx.__pth file, located in your python folder.
  2. Edit the contents (e.g. D:\Pythonx.x.x to the following):
 D:\Pythonx.x.x 
 D:\Pythonx.x.x\DLLs
 D:\Pythonx.x.x\lib
 D:\Pythonx.x.x\lib\plat-win 
 D:\Pythonx.x.x\lib\site-packages

error: request for member '..' in '..' which is of non-class type

I was having a similar error, it seems that the compiler misunderstand the call to the constructor without arguments. I made it work by removing the parenthesis from the variable declaration, in your code something like this:

class Foo
{
  public:
    Foo() {};
    Foo(int a) {};
    void bar() {};
};

int main()
{
  // this works...
  Foo foo1(1);
  foo1.bar();

  // this does not...
  Foo foo2; // Without "()" 
  foo2.bar();

  return 0;
}

Invalid hook call. Hooks can only be called inside of the body of a function component

React linter assumes every method starting with use as hooks and hooks doesn't work inside classes. by renaming const useStyles into anything else that doesn't starts with use like const myStyles you are good to go.

Update:

makeStyles is hook api and you can't use that inside classes. you can use styled components API. see here

Error C1083: Cannot open include file: 'stdafx.h'

You have to properly understand what is a "stdafx.h", aka precompiled header. Other questions or Wikipedia will answer that. In many cases a precompiled header can be avoided, especially if your project is small and with few dependencies. In your case, as you probably started from a template project, it was used to include Windows.h only for the _TCHAR macro.

Then, precompiled header is usually a per-project file in Visual Studio world, so:

  1. Ensure you have the file "stdafx.h" in your project. If you don't (e.g. you removed it) just create a new temporary project and copy the default one from there;
  2. Change the #include <stdafx.h> to #include "stdafx.h". It is supposed to be a project local file, not to be resolved in include directories.

Secondly: it's inadvisable to include the precompiled header in your own headers, to not clutter namespace of other source that can use your code as a library, so completely remove its inclusion in vector.h.

How to delete all files and folders in a directory?

Using just static methods with File and Directory instead of FileInfo and DirectoryInfo will perform faster. (see accepted answer at What is the difference between File and FileInfo in C#?). Answer shown as utility method.

public static void Empty(string directory)
{
    foreach(string fileToDelete in System.IO.Directory.GetFiles(directory))
    {
        System.IO.File.Delete(fileToDelete);
    }
    foreach(string subDirectoryToDeleteToDelete in System.IO.Directory.GetDirectories(directory))
    {
        System.IO.Directory.Delete(subDirectoryToDeleteToDelete, true);
    }
}

trying to align html button at the center of the my page

Here is the solution as asked

_x000D_
_x000D_
<button type="button" style="background-color:yellow;margin:auto;display:block">mybuttonname</button>
_x000D_
_x000D_
_x000D_

Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.10:test

I faced the same error, but in my case, the problem was resolved after deleting the /target folder and nbactions.xml file.

Microsoft Web API: How do you do a Server.MapPath?

As an aside to those that stumble along across this, one nice way to run test level on using the HostingEnvironment call, is if accessing say a UNC share: \example\ that is mapped to ~/example/ you could execute this to get around IIS-Express issues:

#if DEBUG
    var fs = new FileStream(@"\\example\file",FileMode.Open, FileAccess.Read);
#else
    var fs = new FileStream(HostingEnvironment.MapPath("~/example/file"), FileMode.Open, FileAccess.Read);
#endif

I find that helpful in case you have rights to locally test on a file, but need the env mapping once in production.

Byte Array to Hex String

If you have a numpy array, you can do the following:

>>> import numpy as np
>>> a = np.array([133, 53, 234, 241])
>>> a.astype(np.uint8).data.hex()
'8535eaf1'

How to embed YouTube videos in PHP?

luvboy,

If i understand clearly, user provides the URL/code of the Youtube video and then that video is displayed on the page.

For that, just write a simple page, with layout etc.. Copy video embed code from youtube and paste it in your page. Replace embed code with some field, say VideoID. Set this VideoId to code provided by your user.

edit: see answer by Alec Smart.

How to add default signature in Outlook

The existing answers had a few problems for me:

  1. I needed to insert text (e.g. 'Good Day John Doe') with html formatting where you would normally type your message.
  2. At least on my machine, Outlook adds 2 blank lines above the signature where you should start typing. These should obviously be removed (replaced with custom HTML).

The code below does the job. Please note the following:

  1. The 'From' parameter allows you to choose the account (since there could be different default signatures for different email accounts)
  2. The 'Recipients' parameter expects an array of emails, and it will 'Resolve' the added email (i.e. find it in contacts, as if you had typed it in the 'To' box)
  3. Late binding is used, so no references are required
'Opens an outlook email with the provided email body and default signature
'Parameters:
'  from: Email address of Account to send from.  Wildcards are supported e.g. *@example.com
'  recipients: Array of recipients.  Recipient can be a Contact name or email address
'  subject: Email subject
'  htmlBody: Html formatted body to insert before signature (just body markup, should not contain html, head or body tags)
Public Sub CreateMail(from As String, recipients, subject As String, htmlBody As String)
    Dim oApp, oAcc As Object
    
    Set oApp = CreateObject("Outlook.application")
    
    With oApp.CreateItem(0) 'olMailItem = 0
        'Ensure we are sending with the correct account (to insert the correct signature)
        'oAcc is of type Outlook.Account, which has other properties that could be filtered with if required
        'SmtpAddress is usually equal to the raw email address
        .SendUsingAccount = Nothing
        For Each oAcc In oApp.Session.Accounts
            If CStr(oAcc.SmtpAddress) = from Or CStr(oAcc.SmtpAddress) Like from Then
                Set .SendUsingAccount = oAcc
            End If
        Next oAcc
        If .SendUsingAccount Is Nothing Then Err.Raise -1, , "Unknown email account " & from
        For Each addr In recipients
            With .recipients.Add(addr)
                'This will resolve the recipient as if you had typed the name/email and pressed Tab/Enter
                .Resolve
            End With
        Next addr
        .subject = subject
        .Display 'HTMLBody is only populated after this line
        'Remove blank lines at the top of the body
        .htmlBody = Replace(.htmlBody, "<o:p>&nbsp;</o:p>", "")
        'Insert the html at the start of the 'body' tag
        Dim bodyTagEnd As Long: bodyTagEnd = InStr(InStr(1, .htmlBody, "<body"), .htmlBody, ">")
        .htmlBody = Left(.htmlBody, bodyTagEnd) & htmlBody & Right(.htmlBody, Len(.htmlBody) - bodyTagEnd)
    End With
    Set oApp = Nothing
End Sub

Use as follows:

CreateMail from:="*@contoso.com", _
    recipients:= Array("[email protected]", "Jane Doe", "[email protected]"), _
    subject:= "Test Email", _
    htmlBody:= "<p>Good Day All</p><p>Hello <b>World!</b></p>"

Result:

Sample Outlook Email

ListView item background via custom selector

Never ever use a "background color" for your listview rows...

this will block every selector action (was my problem!)

good luck!

C++ IDE for Macs

Emacs! Eclipse might work too.

How to flush output after each `echo` call?

Sometimes, the problem come from Apache settings. Apache can be set to gzip the output. In the file .htaccess you can add for instance :

SetEnv no-gzip 1

Error: [$injector:unpr] Unknown provider: $routeProvider

It looks like you forgot to include the ngRoute module in your dependency for myApp.

In Angular 1.2, they've made ngRoute optional (so you can use third-party route providers, etc.) and you have to explicitly depend on it in modules, along with including the separate file.

'use strict';

angular.module('myApp', ['ngRoute']).
    config(['$routeProvider', function($routeProvider) {
$routeProvider.otherwise({redirectTo: '/home'});
}]);

Click a button programmatically - JS

The other answers here rely on the user making an initial click (on the image). This is fine for the specifics of the OP detail but not necessarily the question title.

There is an answer here explaining how to do it by firing a click event on the button ( or any element ).

Resize HTML5 canvas to fit window

CSS

body { margin: 0; } 
canvas { display: block; } 

JavaScript

window.addEventListener("load", function()
{
    var canvas = document.createElement('canvas'); document.body.appendChild(canvas);
    var context = canvas.getContext('2d');

    function draw()
    {
        context.clearRect(0, 0, canvas.width, canvas.height);
        context.beginPath();
        context.moveTo(0, 0); context.lineTo(canvas.width, canvas.height); 
        context.moveTo(canvas.width, 0); context.lineTo(0, canvas.height); 
        context.stroke();
    }
    function resize()
    {
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        draw();
    }
    window.addEventListener("resize", resize);
    resize();
});

Setting max width for body using Bootstrap

Edit

A better way to do this is:

  1. Create your own less file as a main less file ( like bootstrap.less ).

  2. Import all bootstrap less files you need. (in this case, you just need to Import all responsive less files but responsive-1200px-min.less)

  3. If you need to modify anything in original bootstrap less file, you just need to write your own less to overwrite bootstrap's less code. (Just remember to put your less code/file after @import { /* bootstrap's less file */ };).

Original

I have the same problem. This is how I fixed it.

Find the media query:

@media (max-width:1200px) ...

Remove it. (I mean the whole thing , not just @media (max-width:1200px))

Since the default width of Bootstrap is 940px, you don't need to do anything.

If you want to have your own max-width, just modify the css rule in the media query that matches your desired width.

How to write macro for Notepad++?

I just did this in v5.9.1. Just go to the Macro Menu, click "Start Recording", perform your 3 replace all commands, then stop recording. You can then select "Save Current Recorded Macro", and play it back as often as you like, and it will perform the replaces as you expect.

Making an iframe responsive

I am search more about this topic and finally get a nice answer. You can try like this:

_x000D_
_x000D_
.wrapper {_x000D_
width: 50%;_x000D_
}_x000D_
.container {_x000D_
height: 0;_x000D_
width: 100%;_x000D_
padding-bottom: 50%;_x000D_
overflow: hidden;_x000D_
position: relative;_x000D_
}_x000D_
.container iframe {_x000D_
top: 0;_x000D_
left: 0;_x000D_
width: 100%;_x000D_
height: 100%;_x000D_
position: absolute;_x000D_
}
_x000D_
<div class="wrapper">_x000D_
  <div class="container">_x000D_
    <iframe src="there is path of your iframe"></iframe>_x000D_
   </div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

How do I use namespaces with TypeScript external modules?

Candy Cup Analogy

Version 1: A cup for every candy

Let's say you wrote some code like this:

Mod1.ts

export namespace A {
    export class Twix { ... }
}

Mod2.ts

export namespace A {
    export class PeanutButterCup { ... }
}

Mod3.ts

export namespace A {
     export class KitKat { ... }
}

You've created this setup: enter image description here

Each module (sheet of paper) gets its own cup named A. This is useless - you're not actually organizing your candy here, you're just adding an additional step (taking it out of the cup) between you and the treats.


Version 2: One cup in the global scope

If you weren't using modules, you might write code like this (note the lack of export declarations):

global1.ts

namespace A {
    export class Twix { ... }
}

global2.ts

namespace A {
    export class PeanutButterCup { ... }
}

global3.ts

namespace A {
     export class KitKat { ... }
}

This code creates a merged namespace A in the global scope:

enter image description here

This setup is useful, but doesn't apply in the case of modules (because modules don't pollute the global scope).


Version 3: Going cupless

Going back to the original example, the cups A, A, and A aren't doing you any favors. Instead, you could write the code as:

Mod1.ts

export class Twix { ... }

Mod2.ts

export class PeanutButterCup { ... }

Mod3.ts

export class KitKat { ... }

to create a picture that looks like this:

enter image description here

Much better!

Now, if you're still thinking about how much you really want to use namespace with your modules, read on...


These Aren't the Concepts You're Looking For

We need to go back to the origins of why namespaces exist in the first place and examine whether those reasons make sense for external modules.

Organization: Namespaces are handy for grouping together logically-related objects and types. For example, in C#, you're going to find all the collection types in System.Collections. By organizing our types into hierarchical namespaces, we provide a good "discovery" experience for users of those types.

Name Conflicts: Namespaces are important to avoid naming collisions. For example, you might have My.Application.Customer.AddForm and My.Application.Order.AddForm -- two types with the same name, but a different namespace. In a language where all identifiers exist in the same root scope and all assemblies load all types, it's critical to have everything be in a namespace.

Do those reasons make sense in external modules?

Organization: External modules are already present in a file system, necessarily. We have to resolve them by path and filename, so there's a logical organization scheme for us to use. We can have a /collections/generic/ folder with a list module in it.

Name Conflicts: This doesn't apply at all in external modules. Within a module, there's no plausible reason to have two objects with the same name. From the consumption side, the consumer of any given module gets to pick the name that they will use to refer to the module, so accidental naming conflicts are impossible.


Even if you don't believe that those reasons are adequately addressed by how modules work, the "solution" of trying to use namespaces in external modules doesn't even work.

Boxes in Boxes in Boxes

A story:

Your friend Bob calls you up. "I have a great new organization scheme in my house", he says, "come check it out!". Neat, let's go see what Bob has come up with.

You start in the kitchen and open up the pantry. There are 60 different boxes, each labelled "Pantry". You pick a box at random and open it. Inside is a single box labelled "Grains". You open up the "Grains" box and find a single box labelled "Pasta". You open the "Pasta" box and find a single box labelled "Penne". You open this box and find, as you expect, a bag of penne pasta.

Slightly confused, you pick up an adjacent box, also labelled "Pantry". Inside is a single box, again labelled "Grains". You open up the "Grains" box and, again, find a single box labelled "Pasta". You open the "Pasta" box and find a single box, this one is labelled "Rigatoni". You open this box and find... a bag of rigatoni pasta.

"It's great!" says Bob. "Everything is in a namespace!".

"But Bob..." you reply. "Your organization scheme is useless. You have to open up a bunch of boxes to get to anything, and it's not actually any more convenient to find anything than if you had just put everything in one box instead of three. In fact, since your pantry is already sorted shelf-by-shelf, you don't need the boxes at all. Why not just set the pasta on the shelf and pick it up when you need it?"

"You don't understand -- I need to make sure that no one else puts something that doesn't belong in the 'Pantry' namespace. And I've safely organized all my pasta into the Pantry.Grains.Pasta namespace so I can easily find it"

Bob is a very confused man.

Modules are Their Own Box

You've probably had something similar happen in real life: You order a few things on Amazon, and each item shows up in its own box, with a smaller box inside, with your item wrapped in its own packaging. Even if the interior boxes are similar, the shipments are not usefully "combined".

Going with the box analogy, the key observation is that external modules are their own box. It might be a very complex item with lots of functionality, but any given external module is its own box.


Guidance for External Modules

Now that we've figured out that we don't need to use 'namespaces', how should we organize our modules? Some guiding principles and examples follow.

Export as close to top-level as possible

  • If you're only exporting a single class or function, use export default:

MyClass.ts

export default class SomeType {
  constructor() { ... }
}

MyFunc.ts

function getThing() { return 'thing'; }
export default getThing;

Consumption

import t from './MyClass';
import f from './MyFunc';
var x = new t();
console.log(f());

This is optimal for consumers. They can name your type whatever they want (t in this case) and don't have to do any extraneous dotting to find your objects.

  • If you're exporting multiple objects, put them all at top-level:

MyThings.ts

export class SomeType { ... }
export function someFunc() { ... }

Consumption

import * as m from './MyThings';
var x = new m.SomeType();
var y = m.someFunc();
  • If you're exporting a large number of things, only then should you use the module/namespace keyword:

MyLargeModule.ts

export namespace Animals {
  export class Dog { ... }
  export class Cat { ... }
}
export namespace Plants {
  export class Tree { ... }
}

Consumption

import { Animals, Plants} from './MyLargeModule';
var x = new Animals.Dog();

Red Flags

All of the following are red flags for module structuring. Double-check that you're not trying to namespace your external modules if any of these apply to your files:

  • A file whose only top-level declaration is export module Foo { ... } (remove Foo and move everything 'up' a level)
  • A file that has a single export class or export function that isn't export default
  • Multiple files that have the same export module Foo { at top-level (don't think that these are going to combine into one Foo!)

Convert string to Python class object?

I've looked at how django handles this

django.utils.module_loading has this

def import_string(dotted_path):
    """
    Import a dotted module path and return the attribute/class designated by the
    last name in the path. Raise ImportError if the import failed.
    """
    try:
        module_path, class_name = dotted_path.rsplit('.', 1)
    except ValueError:
        msg = "%s doesn't look like a module path" % dotted_path
        six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])

    module = import_module(module_path)

    try:
        return getattr(module, class_name)
    except AttributeError:
        msg = 'Module "%s" does not define a "%s" attribute/class' % (
            module_path, class_name)
        six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])

You can use it like import_string("module_path.to.all.the.way.to.your_class")

Clone() vs Copy constructor- which is recommended in java

See also: How to properly override clone method?. Cloning is broken in Java, it's so hard to get it right, and even when it does it doesn't really offer much, so it's not really worth the hassle.

Psql could not connect to server: No such file or directory, 5432 error?

This works for me:

pg_ctl -D /usr/local/var/[email protected] stop;
brew services stop [email protected];
brew services start [email protected];

Using Python 3 in virtualenv

On Mac I had to do the following to get it to work.

mkvirtualenv --python=/usr/bin/python3 YourEnvNameHere

How to make Bootstrap Panel body with fixed height

You can use max-height in an inline style attribute, as below:

<div class="panel panel-primary">
  <div class="panel-heading">jhdsahfjhdfhs</div>
  <div class="panel-body" style="max-height: 10;">fdoinfds sdofjohisdfj</div>
</div>

To use scrolling with content that overflows a given max-height, you can alternatively try the following:

<div class="panel panel-primary">
  <div class="panel-heading">jhdsahfjhdfhs</div>
  <div class="panel-body" style="max-height: 10;overflow-y: scroll;">fdoinfds sdofjohisdfj</div>
</div>

To restrict the height to a fixed value you can use something like this.

<div class="panel panel-primary">
  <div class="panel-heading">jhdsahfjhdfhs</div>
  <div class="panel-body" style="min-height: 10; max-height: 10;">fdoinfds sdofjohisdfj</div>
</div>

Specify the same value for both max-height and min-height (either in pixels or in points – as long as it’s consistent).

You can also put the same styles in css class in a stylesheet (or a style tag as shown below) and then include the same in your tag. See below:

Style Code:

.fixed-panel {
  min-height: 10;
  max-height: 10;
  overflow-y: scroll;
}

Apply Style :

<div class="panel panel-primary">
  <div class="panel-heading">jhdsahfjhdfhs</div>
  <div class="panel-body fixed-panel">fdoinfds sdofjohisdfj</div>
</div>

Hope this helps with your need.

how to configure apache server to talk to HTTPS backend server?

In my case, my server was configured to work only in https mode, and error occured when I try to access http mode. So changing http://my-service to https://my-service helped.

How can I roll back my last delete command in MySQL?

A "rollback" only works if you used transactions. That way you can group queries together and undo all queries if only one of them fails.

But if you already committed the transaction (or used a regular DELETE-query), the only way of getting your data back is to recover it from a previously made backup.

Error:Conflict with dependency 'com.google.code.findbugs:jsr305'

The problem, as stated in your logs, is 2 dependencies trying to use different versions of 3rd dependency. Add one of the following to the app-gradle file:

androidTestCompile 'com.google.code.findbugs:jsr305:2.0.1'
androidTestCompile 'com.google.code.findbugs:jsr305:1.3.9'

How to import a single table in to mysql database using command line

All of these options are fine, if you have the option to re-export the data.

But if you need to use an existing SQL file, and use a specific table from it, then this perl script in the TimeSheet blog, with enable you to extract the table to a separate SQL file, and then import it.

The original link is dead, so it is a good thing that someone has put it instead of the author, Jared Cheney, on GitHub, in this link.

PHP mysql insert date format

The simplest method is

$dateArray = explode('/', $_POST['date']);
$date = $dateArray[2].'-'.$dateArray[0].'-'.$dateArray[1];

$sql = mysql_query("INSERT INTO user_date (column,column,column) VALUES('',$name,$date)") or die (mysql_error());

Am I trying to connect to a TLS-enabled daemon without TLS?

On Ubuntu after installing lxc-docker you need to add your user to the docker user group:

sudo usermod -a -G docker myusername

This is because of the socket file permissions:

srw-rw---- 1 root docker 0 Mar 20 07:43 /var/run/docker.sock

DO NOT RUN usermod WITHOUT "-a" as suggested in one of the other comments or it will wipe your additional groups setting and will just leave the "docker" group

This is what will happen:

?  ~  id pawel
uid=1000(pawel) gid=1000(pawel) groups=1000(pawel),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),124(sambashare),998(docker)
?  ~  usermod -G docker pawel
?  ~  id pawel               
uid=1000(pawel) gid=1000(pawel) groups=1000(pawel),998(docker)

How do I share a global variable between c files?

Use the extern keyword to declare the variable in the other .c file. E.g.:

extern int counter;

means that the actual storage is located in another file. It can be used for both variables and function prototypes.

Perform commands over ssh with Python

Have a look at spurplus, a wrapper we developed around spur that provides type annotations and some minor gimmicks (reconnecting SFTP, md5 etc.): https://pypi.org/project/spurplus/

How to set variable from a SQL query?

There are three approaches:

  1. DECLARE
  2. SET -- Microsoft Recommended approach
  3. SELECT

Below query details the advantage and disadvantage of each:

-- First way, 
DECLARE @test int = (SELECT 1)
       , @test2 int = (SELECT a from (values (1),(2)) t(a)) -- throws error

-- advantage: declare and set in the same place
-- Disadvantage: can be used only during declaration. cannot be used later

-- Second way
DECLARE @test int  
       , @test2 int 

SET @test = (select 1)
SET @test2 = (SELECT a from (values (1),(2)) t(a)) -- throws error

-- Advantage: ANSI standard. 
-- Disadvantage: cannot set more than one variable at a time

-- Third way
DECLARE @test int, @test2 int 
SELECT @test = (select 1)
      ,@test2 = (SELECT a from (values (1),(2)) t(a)) -- throws error

-- Advantage: Can set more than one variable at a time
-- Disadvantage: Not ANSI standard

FFmpeg: How to split video efficiently?

one simple way is to use trim option with publitio url-based api.

once you get your video uploaded, just set start offset and end offset in url (so_2,eo_2) like so:

    https://media.publit.io/file/so_2,eo_2/tummy.mp4

this will create instantly new videos starting from 2nd second and 2 seconds in length. you can split videos this way anyway you like.

React-Native Button style not work

React Native buttons are very limited in the option they provide.You can use TouchableHighlight or TouchableOpacity by styling these element and wrapping your buttons with it like this

             <TouchableHighlight 
                style ={{
                    height: 40,
                    width:160,
                    borderRadius:10,
                    backgroundColor : "yellow",
                    marginLeft :50,
                    marginRight:50,
                    marginTop :20
                }}>
            <Button onPress={this._onPressButton}            
            title="SAVE"
            accessibilityLabel="Learn more about this button"
          /> 
          </TouchableHighlight> 

You can also use react library for customised button .One nice library is react-native-button (https://www.npmjs.com/package/react-native-button)

Angular2 material dialog has issues - Did you add it to @NgModule.entryComponents?

In my case, I added my component to declarations and entryComponents and got the same errors. I also needed to add MatDialogModule to imports.

show all tables in DB2 using the LIST command

have you installed a user db2inst2, i think, i remember, that db2inst1 is very administrative

Free tool to Create/Edit PNG Images?

Paint.NET will create and edit PNGs with gusto. It's an excellent program in many respects. It's free as in beer and speech.

VBA to copy a file from one directory to another

Use the appropriate methods in Scripting.FileSystemObject. Then your code will be more portable to VBScript and VB.net. To get you started, you'll need to include:

Dim fso As Object
Set fso = VBA.CreateObject("Scripting.FileSystemObject")

Then you could use

Call fso.CopyFile(source, destination[, overwrite] )

where source and destination are the full names (including paths) of the file.

See https://docs.microsoft.com/en-us/office/vba/Language/Reference/user-interface-help/copyfile-method

A TypeScript GUID class?

There is an implementation in my TypeScript utilities based on JavaScript GUID generators.

Here is the code:

_x000D_
_x000D_
class Guid {_x000D_
  static newGuid() {_x000D_
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {_x000D_
      var r = Math.random() * 16 | 0,_x000D_
        v = c == 'x' ? r : (r & 0x3 | 0x8);_x000D_
      return v.toString(16);_x000D_
    });_x000D_
  }_x000D_
}_x000D_
_x000D_
// Example of a bunch of GUIDs_x000D_
for (var i = 0; i < 100; i++) {_x000D_
  var id = Guid.newGuid();_x000D_
  console.log(id);_x000D_
}
_x000D_
_x000D_
_x000D_

Please note the following:

C# GUIDs are guaranteed to be unique. This solution is very likely to be unique. There is a huge gap between "very likely" and "guaranteed" and you don't want to fall through this gap.

JavaScript-generated GUIDs are great to use as a temporary key that you use while waiting for a server to respond, but I wouldn't necessarily trust them as the primary key in a database. If you are going to rely on a JavaScript-generated GUID, I would be tempted to check a register each time a GUID is created to ensure you haven't got a duplicate (an issue that has come up in the Chrome browser in some cases).