Programs & Examples On #Security context

concatenate two strings

The best way in my eyes is to use the concat() method provided by the String class itself.

The useage would, in your case, look like this:

String myConcatedString = cursor.getString(numcol).concat('-').
       concat(cursor.getString(cursor.getColumnIndexOrThrow(db.KEY_DESTINATIE)));

List append() in for loop

The list.append function does not return any value(but None), it just adds the value to the list you are using to call that method.

In the first loop round you will assign None (because the no-return of append) to a, then in the second round it will try to call a.append, as a is None it will raise the Exception you are seeing

You just need to change it to:

a=[]
for i in range(5):    
    a.append(i)
print(a)
# [0, 1, 2, 3, 4]

list.append is what is called a mutating or destructive method, i.e. it will destroy or mutate the previous object into a new one(or a new state).

If you would like to create a new list based in one list without destroying or mutating it you can do something like this:

a=['a', 'b', 'c']
result = a + ['d']

print result
# ['a', 'b', 'c', 'd']

print a
# ['a', 'b', 'c']

As a corollary only, you can mimic the append method by doing the following:

a=['a', 'b', 'c']
a = a + ['d']

print a
# ['a', 'b', 'c', 'd']

Getting HTTP code in PHP using curl

use this hitCurl method for fetch all type of api response i.e. Get / Post

        function hitCurl($url,$param = [],$type = 'POST'){
        $ch = curl_init();
        if(strtoupper($type) == 'GET'){
            $param = http_build_query((array)$param);
            $url = "{$url}?{$param}";
        }else{
            curl_setopt_array($ch,[
                CURLOPT_POST => (strtoupper($type) == 'POST'),
                CURLOPT_POSTFIELDS => (array)$param,
            ]);
        }
        curl_setopt_array($ch,[
            CURLOPT_URL => $url,
            CURLOPT_RETURNTRANSFER => true,
        ]);
        $resp = curl_exec($ch);
        $statusCode = curl_getinfo($ch,CURLINFO_HTTP_CODE);
        curl_close($ch);
        return [
            'statusCode' => $statusCode,
            'resp' => $resp
        ];
    }

Demo function to test api

 function fetchApiData(){
        $url = 'https://postman-echo.com/get';
        $resp = $this->hitCurl($url,[
            'foo1'=>'bar1',
            'foo2'=>'bar2'
        ],'get');
        $apiData = "Getting header code {$resp['statusCode']}";
        if($resp['statusCode'] == 200){
            $apiData = json_decode($resp['resp']);
        }
        echo "<pre>";
        print_r ($apiData);
        echo "</pre>";
    }

How do you get the current project directory from C# code when creating a custom MSBuild task?

Yet another imperfect solution (but perhaps a little closer to perfect than some of the others):

    protected static string GetSolutionFSPath() {
        return System.IO.Directory.GetParent(System.IO.Directory.GetCurrentDirectory()).Parent.Parent.FullName;
    }
    protected static string GetProjectFSPath() {
        return String.Format("{0}\\{1}", GetSolutionFSPath(), System.Reflection.Assembly.GetExecutingAssembly().GetName().Name);
    }

This version will return the current projects' folder even if the current project is not the Startup Project for the solution.

The first flaw with this is that I've skipped all error checking. That can be fixed easy enough but should only be a problem if you're storing your project in the root directory for the drive or using a junction in your path (and that junction is a descendant of the solution folder) so this scenario is unlikely. I'm not entirely sure that Visual Studio could handle either of these setups anyway.

Another (more likely) problem that you may run into is that the project name must match the folder name for the project for it to be found.

Another problem you may have is that the project must be inside the solution folder. This usually isn't a problem but if you've used the Add Existing Project to Solution option to add the project to the solution then this may not be the way your solution is organized.

Lastly, if you're application will be modifying the working directory, you should store this value before you do that because this value is determined relative to the current working directory.

Of course, this all also means that you must not alter the default values for your projects' Build->Output path or Debug->Working directory options in the project properties dialog.

Mixing C# & VB In The Same Project

No, you can't. An assembly/project (each project compiles to 1 assembly usually) has to be one language. However, you can use multiple assemblies, and each can be coded in a different language because they are all compiled to CIL.

It compiled fine and didn't complain because a VB.NET project will only actually compile the .vb files and a C# project will only actually compile the .cs files. It was ignoring the other ones, therefore you did not receive errors.

Edit: If you add a .vb file to a C# project, select the file in the Solution Explorer panel and then look at the Properties panel, you'll notice that the Build Action is 'Content', not 'Compile'. It is treated as a simple text file and doesn't even get embedded in the compiled assembly as a binary resource.

Edit: With asp.net websites you may add c# web user control to vb.net website

moment.js - UTC gives wrong date

By default, MomentJS parses in local time. If only a date string (with no time) is provided, the time defaults to midnight.

In your code, you create a local date and then convert it to the UTC timezone (in fact, it makes the moment instance switch to UTC mode), so when it is formatted, it is shifted (depending on your local time) forward or backwards.

If the local timezone is UTC+N (N being a positive number), and you parse a date-only string, you will get the previous date.

Here are some examples to illustrate it (my local time offset is UTC+3 during DST):

>>> moment('07-18-2013', 'MM-DD-YYYY').utc().format("YYYY-MM-DD HH:mm")
"2013-07-17 21:00"
>>> moment('07-18-2013 12:00', 'MM-DD-YYYY HH:mm').utc().format("YYYY-MM-DD HH:mm")
"2013-07-18 09:00"
>>> Date()
"Thu Jul 25 2013 14:28:45 GMT+0300 (Jerusalem Daylight Time)"

If you want the date-time string interpreted as UTC, you should be explicit about it:

>>> moment(new Date('07-18-2013 UTC')).utc().format("YYYY-MM-DD HH:mm")
"2013-07-18 00:00"

or, as Matt Johnson mentions in his answer, you can (and probably should) parse it as a UTC date in the first place using moment.utc() and include the format string as a second argument to prevent ambiguity.

>>> moment.utc('07-18-2013', 'MM-DD-YYYY').format("YYYY-MM-DD HH:mm")
"2013-07-18 00:00"

To go the other way around and convert a UTC date to a local date, you can use the local() method, as follows:

>>> moment.utc('07-18-2013', 'MM-DD-YYYY').local().format("YYYY-MM-DD HH:mm")
"2013-07-18 03:00"

Replacing from match to end-of-line

This should do what you want:

sed 's/two.*/BLAH/'

$ echo "   one  two  three  five
>    four two  five five six
>    six  one  two seven four" | sed 's/two.*/BLAH/'
   one  BLAH
   four BLAH
   six  one  BLAH

The $ is unnecessary because the .* will finish at the end of the line anyways, and the g at the end is unnecessary because your first match will be the first two to the end of the line.

JavaScript - Getting HTML form values

HTML:

<input type="text" name="name" id="uniqueID" value="value" />

JS:

var nameValue = document.getElementById("uniqueID").value;

Python causing: IOError: [Errno 28] No space left on device: '../results/32766.html' on disk with lots of space

In my case, when I run df -i it shows me that my number of inodes are full and then I have to delete some of the small files or folder. Otherwise it will not allow us to create files or folders once inodes get full.

All you have to do is delete files or folder that has not taken up full space but is responsible for filling inodes.

Is a slash ("/") equivalent to an encoded slash ("%2F") in the path portion of an HTTP URL

I also have a site that has numerous urls with urlencoded characters. I am finding that many web APIs (including Google webmaster tools and several Drupal modules) trip over urlencoded characters. Many APIs automatically decode urls at some point in their process and then use the result as a URL or HTML. When I find one of these problems, I usually double encode the results (which turns %2f into %252f) for that API. However, this will break other APIs which are not expecting double encoding, so this is not a universal solution.

Personally I am getting rid of as many special characters in my URLs as possible.

Also, I am using id numbers in my URLs which do not depend on urldecoding:

example.com/blog/my-amazing-blog%2fstory/yesterday

becomes:

example.com/blog/12354/my-amazing-blog%2fstory/yesterday

in this case, my code only uses 12354 to look for the article, and the rest of the URL gets ignored by my system (but is still used for SEO.) Also, this number should appear BEFORE the unused URL components. that way, the url will still work, even if the %2f gets decoded incorrectly.

Also, be sure to use canonical tags to ensure that url mistakes don't translate into duplicate content.

enable or disable checkbox in html

I know this question is a little old but here is my solution.

 // HTML
 // <input type="checkbox" onClick="setcb1()"/>
 // <input type="checkbox" onClick="setcb2()"/>

 // cb1 = checkbox 1
 // cb2 = checkbox 2
  var cb1 = getId('cb1'), 
      cb2 = getId('cb2');

  function getId(id) {
    return document.getElementById(id);
  }

  function setcb1() {
    if(cb1.checked === true) {
      cb2.checked = false;
      cb2.disabled = "disabled"; // You have to disable the unselected checkbox
    } else if(cb1.checked === false) {
      cb2.disabled = ""; // Then enable it if there isn't one selected.  
    }
  }

  function setcb2() {
    if(cb2.checked === true) {
      cb1.checked = false;
      cb1.disabled = "disabled"
    } else if(cb2.checked === false) {
      cb1.disabled = ""
  }

Hope this helps!

What is the difference between venv, pyvenv, pyenv, virtualenv, virtualenvwrapper, pipenv, etc?

Let's start with the problems these tools want to solve:

My system package manager don't have the Python versions I wanted or I want to install multiple Python versions side by side, Python 3.9.0 and Python 3.9.1, Python 3.5.3, etc

Then use pyenv.

I want to install and run multiple applications with different, conflicting dependencies.

Then use virtualenv or venv. These are almost completely interchangeable, the difference being that virtualenv supports older python versions and has a few more minor unique features, while venv is in the standard library.

I'm developing an /application/ and need to manage my dependencies, and manage the dependency resolution of the dependencies of my project.

Then use pipenv or poetry.

I'm developing a /library/ or a /package/ and want to specify the dependencies that my library users need to install

Then use setuptools.

I used virtualenv, but I don't like virtualenv folders being scattered around various project folders. I want a centralised management of the environments and some simple project management

Then use virtualenvwrapper. Variant: pyenv-virtualenvwrapper if you also use pyenv.


Not recommended

  • pyvenv. This is deprecated, use venv or virtualenv instead. Not to be confused with pipenv or pyenv.

How do I run a Java program from the command line on Windows?

It is easy. If you have saved your file as A.text first thing you should do is save it as A.java. Now it is a Java file.

Now you need to open cmd and set path to you A.java file before compile it. you can refer this for that.

Then you can compile your file using command

javac A.java

Then run it using

java A

So that is how you compile and run a java program in cmd. You can also go through these material that is Java in depth lessons. Lot of things you need to understand in Java is covered there for beginners.

iPhone 6 Plus resolution confusion: Xcode or Apple's website? for development

Even if I don't generally like the tone of John Gruber's Daring Fireball blog, his Larger iPhone Display Conjecture is well worth the read.

He guessed but got exactly right both the resolution in points and in pixels for both models, except that he did not (me neither) expect Apple to build a smaller resolution physical display and scale down (details are in @Tommy's answer).

The gist of it all is that one should stop thinking in terms of pixels and start thinking in terms of points (this has been the case for quite some time, it's not a recent invention) and resulting physical size of UI elements. In short, both new iPhone models improve in this regard as physically most elements remain the same size, you can just fit more of them on the screen (for each bigger screen you can fit more).

I'm just slightly disappointed they haven't kept mapping of internal resolution to actual screen resolution 1:1 for the bigger model.

XML Error: There are multiple root elements

You can do it without modifying the XML stream: Tell the XmlReader to not be so picky. Setting the XmlReaderSettings.ConformanceLevel to ConformanceLevel.Fragment will let the parser ignore the fact that there is no root node.

        XmlReaderSettings settings = new XmlReaderSettings();
        settings.ConformanceLevel = ConformanceLevel.Fragment;
        using (XmlReader reader = XmlReader.Create(tr,settings))
        {
             ...
        }

Now you can parse something like this (which is an real time XML stream, where it is impossible to wrap with a node).

<event>
  <timeStamp>1354902435238</timeStamp>
  <eventId>7073822</eventId>
</event>
<data>
  <time>1354902435341</time>
  <payload type='80'>7d1300786a0000000bf9458b0518000000000000000000000000000000000c0c030306001b</payload>
</data>
<data>
  <time>1354902435345</time>
  <payload type='80'>fd1260780912ff3028fea5ffc0387d640fa550f40fbdf7afffe001fff8200fff00f0bf0e000042201421100224ff40312300111400004f000000e0c0fbd1e0000f10e0fccc2ff0000f0fe00f00f0eed00f11e10d010021420401</payload>
</data>
<data>
  <time>1354902435347</time>
  <payload type='80'>fd126078ad11fc4015fefdf5b042ff1010223500000000000000003007ff00f20e0f01000e0000dc0f01000f000000000000004f000000f104ff001000210f000013010000c6da000000680ffa807800200000000d00c0f0</payload>
</data>

Authentication versus Authorization

Authentication is the process of ascertaining that somebody really is who they claim to be.

Authorization refers to rules that determine who is allowed to do what. E.g. Adam may be authorized to create and delete databases, while Usama is only authorised to read.

The two concepts are completely orthogonal and independent, but both are central to security design, and the failure to get either one correct opens up the avenue to compromise.

In terms of web apps, very crudely speaking, authentication is when you check login credentials to see if you recognize a user as logged in, and authorization is when you look up in your access control whether you allow the user to view, edit, delete or create content.

pandas GroupBy columns with NaN (missing) values

I answered this already, but some reason the answer was converted to a comment. Nevertheless, this is the most efficient solution:

Not being able to include (and propagate) NaNs in groups is quite aggravating. Citing R is not convincing, as this behavior is not consistent with a lot of other things. Anyway, the dummy hack is also pretty bad. However, the size (includes NaNs) and the count (ignores NaNs) of a group will differ if there are NaNs.

dfgrouped = df.groupby(['b']).a.agg(['sum','size','count'])

dfgrouped['sum'][dfgrouped['size']!=dfgrouped['count']] = None

When these differ, you can set the value back to None for the result of the aggregation function for that group.

How do I clone a Django model instance object and save it to the database?

setting pk to None is better, sinse Django can correctly create a pk for you

object_copy = MyObject.objects.get(pk=...)
object_copy.pk = None
object_copy.save()

TextFX menu is missing in Notepad++

Plugins -> Plugin Manager -> Show Plugin Manager -> Setting -> Check mark On Force HTTP instead of HTTPS for downloading Plugin List & Use development plugin list (may contain untested, unvalidated or un-installable plugins). -> OK.

Capitalize the first letter of string in AngularJs

_x000D_
_x000D_
.capitalize {_x000D_
  display: inline-block;_x000D_
}_x000D_
_x000D_
.capitalize:first-letter {_x000D_
  font-size: 2em;_x000D_
  text-transform: capitalize;_x000D_
}
_x000D_
<span class="capitalize">_x000D_
  really, once upon a time there was a badly formatted output coming from my backend, <strong>all completely in lowercase</strong> and thus not quite as fancy-looking as could be - but then cascading style sheets (which we all know are <a href="http://9gag.com/gag/6709/css-is-awesome">awesome</a>) with modern pseudo selectors came around to the rescue..._x000D_
</span>
_x000D_
_x000D_
_x000D_

How return error message in spring mvc @Controller

As Sotirios Delimanolis already pointed out in the comments, there are two options:

Return ResponseEntity with error message

Change your method like this:

@RequestMapping(method = RequestMethod.GET)
public ResponseEntity getUser(@RequestHeader(value="Access-key") String accessKey,
                              @RequestHeader(value="Secret-key") String secretKey) {
    try {
        // see note 1
        return ResponseEntity
            .status(HttpStatus.CREATED)                 
            .body(this.userService.chkCredentials(accessKey, secretKey, timestamp));
    }
    catch(ChekingCredentialsFailedException e) {
        e.printStackTrace(); // see note 2
        return ResponseEntity
            .status(HttpStatus.FORBIDDEN)
            .body("Error Message");
    }
}

Note 1: You don't have to use the ResponseEntity builder but I find it helps with keeping the code readable. It also helps remembering, which data a response for a specific HTTP status code should include. For example, a response with the status code 201 should contain a link to the newly created resource in the Location header (see Status Code Definitions). This is why Spring offers the convenient build method ResponseEntity.created(URI).

Note 2: Don't use printStackTrace(), use a logger instead.

Provide an @ExceptionHandler

Remove the try-catch block from your method and let it throw the exception. Then create another method in a class annotated with @ControllerAdvice like this:

@ControllerAdvice
public class ExceptionHandlerAdvice {

    @ExceptionHandler(ChekingCredentialsFailedException.class)
    public ResponseEntity handleException(ChekingCredentialsFailedException e) {
        // log exception
        return ResponseEntity
                .status(HttpStatus.FORBIDDEN)
                .body("Error Message");
    }        
}

Note that methods which are annotated with @ExceptionHandler are allowed to have very flexible signatures. See the Javadoc for details.

Create Pandas DataFrame from a string

Simplest way is to save it to temp file and then read it:

import pandas as pd

CSV_FILE_NAME = 'temp_file.csv'  # Consider creating temp file, look URL below
with open(CSV_FILE_NAME, 'w') as outfile:
    outfile.write(TESTDATA)
df = pd.read_csv(CSV_FILE_NAME, sep=';')

Right way of creating temp file: How can I create a tmp file in Python?

How to make an authenticated web request in Powershell?

The PowerShell is almost exactly the same.

$webclient = new-object System.Net.WebClient
$webclient.Credentials = new-object System.Net.NetworkCredential($username, $password, $domain)
$webpage = $webclient.DownloadString($url)

How can I maintain fragment state when added to the back stack?

Here, since onSaveInstanceState in fragment does not call when you add fragment into backstack. The fragment lifecycle in backstack when restored start onCreateView and end onDestroyView while onSaveInstanceState is called between onDestroyView and onDestroy. My solution is create instance variable and init in onCreate. Sample code:

private boolean isDataLoading = true;
private ArrayList<String> listData;
public void onCreate(Bundle savedInstanceState){
     super.onCreate(savedInstanceState);
     isDataLoading = false;
     // init list at once when create fragment
     listData = new ArrayList();
}

And check it in onActivityCreated:

public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    if(isDataLoading){
         fetchData();
    }else{
         //get saved instance variable listData()
    }
}

private void fetchData(){
     // do fetch data into listData
}

Create XML in Javascript

Simply use

var xmlString = '<?xml version="1.0" ?><root />';
var xml = jQuery.parseXML(xml);

It's jQuery.parseXML, so no need to worry about cross-browser tricks. Use jQuery as like HTML, it's using the native XML engine.

Pass table as parameter into sql server UDF

Unfortunately, there is no simple way in SQL Server 2005. Lukasz' answer is correct for SQL Server 2008 though and the feature is long overdue

Any solution would involve temp tables, or passing in xml/CSV and parsing in the UDF. Example: change to xml, parse in udf

DECLARE @psuedotable xml

SELECT
    @psuedotable = ...
FROM
    ...
FOR XML ...

SELECT ... dbo.MyUDF (@psuedotable)

What do you want to do in the bigger picture though? There may be another way to do this...

Edit: Why not pass in the query as a string and use a stored proc with output parameter

Note: this is an untested bit of code, and you'd need to think about SQL injection etc. However, it also satisfies your "one column" requirement and should help you along

CREATE PROC dbo.ToCSV (
    @MyQuery varchar(2000),
    @CSVOut varchar(max)
)
AS
SET NOCOUNT ON

CREATE TABLE #foo (bar varchar(max))

INSERT #foo
EXEC (@MyQuery)

SELECT
    @CSVOut = SUBSTRING(buzz, 2, 2000000000)
FROM
    (
    SELECT 
        bar -- maybe CAST(bar AS varchar(max))??
    FROM 
        #foo
    FOR XML PATH (',')
    ) fizz(buzz)
GO

Duplicate AssemblyVersion Attribute

This issue is a reference conflict which is mostly peculiar to VS 2017.

I solved this same error by simply commenting out lines 7 -14 as well as Assembly version codes at the bottom of the page on AssemblyInfo.cs

It removed all the duplicate references and the project was able to build again.

Python - Dimension of Data Frame

Summary of all ways to get info on dimensions of DataFrame or Series

There are a number of ways to get information on the attributes of your DataFrame or Series.

Create Sample DataFrame and Series

df = pd.DataFrame({'a':[5, 2, np.nan], 'b':[ 9, 2, 4]})
df

     a  b
0  5.0  9
1  2.0  2
2  NaN  4

s = df['a']
s

0    5.0
1    2.0
2    NaN
Name: a, dtype: float64

shape Attribute

The shape attribute returns a two-item tuple of the number of rows and the number of columns in the DataFrame. For a Series, it returns a one-item tuple.

df.shape
(3, 2)

s.shape
(3,)

len function

To get the number of rows of a DataFrame or get the length of a Series, use the len function. An integer will be returned.

len(df)
3

len(s)
3

size attribute

To get the total number of elements in the DataFrame or Series, use the size attribute. For DataFrames, this is the product of the number of rows and the number of columns. For a Series, this will be equivalent to the len function:

df.size
6

s.size
3

ndim attribute

The ndim attribute returns the number of dimensions of your DataFrame or Series. It will always be 2 for DataFrames and 1 for Series:

df.ndim
2

s.ndim
1

The tricky count method

The count method can be used to return the number of non-missing values for each column/row of the DataFrame. This can be very confusing, because most people normally think of count as just the length of each row, which it is not. When called on a DataFrame, a Series is returned with the column names in the index and the number of non-missing values as the values.

df.count() # by default, get the count of each column

a    2
b    3
dtype: int64


df.count(axis='columns') # change direction to get count of each row

0    2
1    2
2    1
dtype: int64

For a Series, there is only one axis for computation and so it just returns a scalar:

s.count()
2

Use the info method for retrieving metadata

The info method returns the number of non-missing values and data types of each column

df.info()

<class 'pandas.core.frame.DataFrame'>
RangeIndex: 3 entries, 0 to 2
Data columns (total 2 columns):
a    2 non-null float64
b    3 non-null int64
dtypes: float64(1), int64(1)
memory usage: 128.0 bytes

How can I customize the tab-to-space conversion factor?

@alex-dima's solution from 2015 will change tab sizes and spaces for all files and @Tricky's solution from 2016 appears to only change the settings for the current file.

As of 2017, I found another solution that works on a per-language basis. Visual Studio Code was not using the proper tab sizes or space settings for Elixir, so I found that I could change the settings for all Elixir files.

I clicked on the language in the status bar ("Elixir" in my case), chose "Configure 'Elixir' language based settings...", and edited the Elixir-specific language settings. I just copied the "editor.tabSize" and "editor.insertSpaces" settings from the default settings on the left (I'm so glad those are shown) and then modified them on the right.

It worked great, and now all Elixir language files use the proper tab size and space settings.

How to copy the first few lines of a giant file, and add a line of text at the end of it using some Linux commands?

I am assuming what you are trying to achieve is to insert a line after the first few lines of of a textfile.

head -n10 file.txt >> newfile.txt
echo "your line >> newfile.txt
tail -n +10 file.txt >> newfile.txt

If you don't want to rest of the lines from the file, just skip the tail part.

Div Background Image Z-Index Issue

To solve the issue, you are using the z-index on the footer and header, but you forgot about the position, if a z-index is to be used, the element must have a position:

Add to your footer and header this CSS:

position: relative; 

EDITED:

Also noticed that the background image on the #backstretch has a negative z-index, don't use that, some browsers get really weird...

Remove From the #backstretch:

z-index: -999999;

Read a little bit about Z-Index here!

Spring Data JPA find by embedded object property

The above - findByBookIdRegion() did not work for me. The following works with the latest release of String Data JPA:

Page<QueuedBook> findByBookId_Region(Region region, Pageable pageable);

pull out p-values and r-squared from a linear regression

Extension of @Vincent 's answer:

For lm() generated models:

summary(fit)$coefficients[,4]   ##P-values 
summary(fit)$r.squared          ##R squared values

For gls() generated models:

summary(fit)$tTable[,4]         ##P-values
##R-squared values are not generated b/c gls uses max-likelihood not Sums of Squares

To isolate an individual p-value itself, you'd add a row number to the code:

For example to access the p-value of the intercept in both model summaries:

summary(fit)$coefficients[1,4]
summary(fit)$tTable[1,4]  
  • Note, you can replace the column number with the column name in each of the above instances:

    summary(fit)$coefficients[1,"Pr(>|t|)"]  ##lm 
    summary(fit)$tTable[1,"p-value"]         ##gls 
    

If you're still unsure of how to access a value form the summary table use str() to figure out the structure of the summary table:

str(summary(fit))

How do I create a timer in WPF?

In WPF, you use a DispatcherTimer.

System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan(0,5,0);
dispatcherTimer.Start();


private void dispatcherTimer_Tick(object sender, EventArgs e)
{
  // code goes here
}

How do you determine what SQL Tables have an identity column programmatically

This query seems to do the trick:

SELECT 
    sys.objects.name AS table_name, 
    sys.columns.name AS column_name
FROM sys.columns JOIN sys.objects 
    ON sys.columns.object_id=sys.objects.object_id
WHERE 
    sys.columns.is_identity=1
    AND
    sys.objects.type in (N'U')

How to set gradle home while importing existing project in Android studio

If you're using MacPorts gradle's home is:

/opt/local/share/java/gradle

PHP: How to check if a date is today, yesterday or tomorrow

Pass the date into the function.

            <?php
                function getTheDay($date)
                {
                    $curr_date=strtotime(date("Y-m-d H:i:s"));
                    $the_date=strtotime($date);
                    $diff=floor(($curr_date-$the_date)/(60*60*24));
                    switch($diff)
                    {
                        case 0:
                            return "Today";
                            break;
                        case 1:
                            return "Yesterday";
                            break;
                        default:
                            return $diff." Days ago";
                    }
                }
            ?>

How to remove all subviews of a view in Swift?

Try this out , I tested this :

  let theSubviews = container_view.subviews
  for subview in theSubviews {
      subview.removeFromSuperview()
  }

Add a column in a table in HIVE QL

You cannot add a column with a default value in Hive. You have the right syntax for adding the column ALTER TABLE test1 ADD COLUMNS (access_count1 int);, you just need to get rid of default sum(max_count). No changes to that files backing your table will happen as a result of adding the column. Hive handles the "missing" data by interpreting NULL as the value for every cell in that column.

So now your have the problem of needing to populate the column. Unfortunately in Hive you essentially need to rewrite the whole table, this time with the column populated. It may be easier to rerun your original query with the new column. Or you could add the column to the table you have now, then select all of its columns plus value for the new column.

You also have the option to always COALESCE the column to your desired default and leave it NULL for now. This option fails when you want NULL to have a meaning distinct from your desired default. It also requires you to depend on always remembering to COALESCE.

If you are very confident in your abilities to deal with the files backing Hive, you could also directly alter them to add your default. In general I would recommend against this because most of the time it will be slower and more dangerous. There might be some case where it makes sense though, so I've included this option for completeness.

Skip Git commit hooks

For those very beginners who has spend few hours for this commit (with comment and no verify) with no further issue

git commit -m "Some comments" --no-verify

PHP AES encrypt / decrypt

If you are using PHP >= 7.2 consider using inbuilt sodium core extension for encrption.

Find more information here - http://php.net/manual/en/intro.sodium.php.

How to add a constant column in a Spark DataFrame?

As the other answers have described, lit and typedLit are how to add constant columns to DataFrames. lit is an important Spark function that you will use frequently, but not for adding constant columns to DataFrames.

You'll commonly be using lit to create org.apache.spark.sql.Column objects because that's the column type required by most of the org.apache.spark.sql.functions.

Suppose you have a DataFrame with a some_date DateType column and would like to add a column with the days between December 31, 2020 and some_date.

Here's your DataFrame:

+----------+
| some_date|
+----------+
|2020-09-23|
|2020-01-05|
|2020-04-12|
+----------+

Here's how to calculate the days till the year end:

val diff = datediff(lit(Date.valueOf("2020-12-31")), col("some_date"))
df
  .withColumn("days_till_yearend", diff)
  .show()
+----------+-----------------+
| some_date|days_till_yearend|
+----------+-----------------+
|2020-09-23|               99|
|2020-01-05|              361|
|2020-04-12|              263|
+----------+-----------------+

You could also use lit to create a year_end column and compute the days_till_yearend like so:

import java.sql.Date

df
  .withColumn("yearend", lit(Date.valueOf("2020-12-31")))
  .withColumn("days_till_yearend", datediff(col("yearend"), col("some_date")))
  .show()
+----------+----------+-----------------+
| some_date|   yearend|days_till_yearend|
+----------+----------+-----------------+
|2020-09-23|2020-12-31|               99|
|2020-01-05|2020-12-31|              361|
|2020-04-12|2020-12-31|              263|
+----------+----------+-----------------+

Most of the time, you don't need to use lit to append a constant column to a DataFrame. You just need to use lit to convert a Scala type to a org.apache.spark.sql.Column object because that's what's required by the function.

See the datediff function signature:

enter image description here

As you can see, datediff requires two Column arguments.

How to get text with Selenium WebDriver in Python

I've found this absolutely invaluable when unable to grab something in a custom class or changing id's:

driver.find_element_by_xpath("//*[contains(text(), 'Show Next Date Available')]").click()
driver.find_element_by_xpath("//*[contains(text(), 'Show Next Date Available')]").text
driver.find_element_by_xpath("//*[contains(text(), 'Available')]").text
driver.find_element_by_xpath("//*[contains(text(), 'Avail')]").text

Angular 2 http post params and body

And it works, thanks @trichetriche. The problem was in my RequestOptions, apparently, you can not pass params or body to the RequestOptions while using the post. Removing one of them gives me an error, removing both and it works. Still no final solution to my problem, but I now have something to work with. Final working code.

public post(cmd: string, data: string): Observable<any> {

    const options = new RequestOptions({
      headers: this.getAuthorizedHeaders(),
      responseType: ResponseContentType.Json,
      withCredentials: false
    });

    console.log('Options: ' + JSON.stringify(options));

    return this.http.post(this.BASE_URL, JSON.stringify({
      cmd: cmd,
      data: data}), options)
      .map(this.handleData)
      .catch(this.handleError);
  }

How can I obfuscate (protect) JavaScript?

If you use a JavaScript library, consider Dojo Toolkit which is compatible (after minor modifications) with the Closure Compiler's Advanced mode compilation.

Dojo – The Only JavaScript Library Compatible with The Closure Compiler

Code compiled with Closure Advanced mode is almost impossible to reverse-engineer, even passing through a beautifier, as the entire code base (includinhg the library) is obfuscated. It is also 25% small on average.

JavaScript code that is merely minified (YUI Compressor, Uglify etc.) is easy to reverse-engineer after passing through a beautifier.

SQL Server 2005 Using CHARINDEX() To split a string

I wouldn't exactly say it is easy or obvious, but with just two hyphens, you can reverse the string and it is not too hard:

with t as (select 'LD-23DSP-1430' as val)
select t.*,
       LEFT(val, charindex('-', val) - 1),
   SUBSTRING(val, charindex('-', val)+1, len(val) - CHARINDEX('-', reverse(val)) - charindex('-', val)),
       REVERSE(LEFT(reverse(val), charindex('-', reverse(val)) - 1))
from t;

Beyond that and you might want to use split() instead.

Disable automatic sorting on the first column when using jQuery DataTables

If any of other solution doesn't fix it, try to override the styles to hide the sort togglers:

.sorting_asc:after, .sorting_desc:after {
  content: "";
}

How to remove index.php from URLs?

Hi I'm late to the party.. just wanted to point out that the instructions from http://davidtsadler.com/archives/2012/06/03/how-to-install-magento-on-ubuntu/ were really useful.

I had Ubuntu server installed with Apache, MySql and Php so I thought I could jump to the heading Creating the directory from which Magento will be served from and I reached the same problem as the OP, i.e. I had 'index.php' needed in all the URLs (or I would get 404 not found). I then went back to Installing and configuring the Apache HTTP server and after restarting apache it works perfectly.

For reference, I was missing:

sudo bash -c "cat >> /etc/apache2/conf.d/servername.conf <<EOF
ServerName localhost
EOF"

... and

sudo a2enmod rewrite
sudo service apache2 restart

Hope this helps

How to split a long array into smaller arrays, with JavaScript

using prototype we can set directly to array class

_x000D_
_x000D_
Array.prototype.chunk = function(n) {_x000D_
  if (!this.length) {_x000D_
    return [];_x000D_
  }_x000D_
  return [this.slice(0, n)].concat(this.slice(n).chunk(n));_x000D_
};_x000D_
console.log([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15].chunk(5));
_x000D_
_x000D_
_x000D_

including parameters in OPENQUERY

declare @p_Id varchar(10)
SET @p_Id = '40381'

EXECUTE ('BEGIN update TableName
                set     ColumnName1 = null,
                        ColumnName2 = null,
                        ColumnName3 = null,
                        ColumnName4 = null
                 where   PERSONID = '+ @p_Id +'; END;') AT [linked_Server_Name]

WooCommerce - get category for product page

Thanks Box. I'm using MyStile Theme and I needed to display the product category name in my search result page. I added this function to my child theme functions.php

Hope it helps others.

/* Post Meta */


if (!function_exists( 'woo_post_meta')) {
    function woo_post_meta( ) {
        global $woo_options;
        global $post;

        $terms = get_the_terms( $post->ID, 'product_cat' );
        foreach ($terms as $term) {
            $product_cat = $term->name;
            break;
        }

?>
<aside class="post-meta">
    <ul>
        <li class="post-category">
            <?php the_category( ', ', $post->ID) ?>
                        <?php echo $product_cat; ?>

        </li>
        <?php the_tags( '<li class="tags">', ', ', '</li>' ); ?>
        <?php if ( isset( $woo_options['woo_post_content'] ) && $woo_options['woo_post_content'] == 'excerpt' ) { ?>
            <li class="comments"><?php comments_popup_link( __( 'Leave a comment', 'woothemes' ), __( '1 Comment', 'woothemes' ), __( '% Comments', 'woothemes' ) ); ?></li>
        <?php } ?>
        <?php edit_post_link( __( 'Edit', 'woothemes' ), '<li class="edit">', '</li>' ); ?>
    </ul>
</aside>
<?php
    }
}


?>

Arduino error: does not name a type?

I got the does not name a type error when installing the NeoMatrix library.

Solution: the .cpp and .h files need to be in the top folder when you copy it, e.g:

myArduinoFolder/libraries/Adafruit_NeoMatrix/Adafruit_NeoMatrix.cpp

When I used the default Windows unzip program, it nested the contents inside another folder:

myArduinoFolder/libraries/Adafruit_NeoMatrix/Adafruit_NeoMatrix/Adafruit_NeoMatrix.cpp

I moved the files up, so it was:

myArduinoFolder/libraries/Adafruit_NeoMatrix/Adafruit_NeoMatrix.cpp

This fixed the does not name a type problem.

Message "Async callback was not invoked within the 5000 ms timeout specified by jest.setTimeout"

For Jest 24.9+, you can also set the timeout from the command line by adding --testTimeout.

Here's an excerpt from its documentation:

--testTimeout=<number>
Default timeout of a test in milliseconds. Default value: 5000.

Getting the last element of a list

In Python, how do you get the last element of a list?

To just get the last element,

  • without modifying the list, and
  • assuming you know the list has a last element (i.e. it is nonempty)

pass -1 to the subscript notation:

>>> a_list = ['zero', 'one', 'two', 'three']
>>> a_list[-1]
'three'

Explanation

Indexes and slices can take negative integers as arguments.

I have modified an example from the documentation to indicate which item in a sequence each index references, in this case, in the string "Python", -1 references the last element, the character, 'n':

 +---+---+---+---+---+---+
 | P | y | t | h | o | n |
 +---+---+---+---+---+---+
   0   1   2   3   4   5 
  -6  -5  -4  -3  -2  -1

>>> p = 'Python'
>>> p[-1]
'n'

Assignment via iterable unpacking

This method may unnecessarily materialize a second list for the purposes of just getting the last element, but for the sake of completeness (and since it supports any iterable - not just lists):

>>> *head, last = a_list
>>> last
'three'

The variable name, head is bound to the unnecessary newly created list:

>>> head
['zero', 'one', 'two']

If you intend to do nothing with that list, this would be more apropos:

*_, last = a_list

Or, really, if you know it's a list (or at least accepts subscript notation):

last = a_list[-1]

In a function

A commenter said:

I wish Python had a function for first() and last() like Lisp does... it would get rid of a lot of unnecessary lambda functions.

These would be quite simple to define:

def last(a_list):
    return a_list[-1]

def first(a_list):
    return a_list[0]

Or use operator.itemgetter:

>>> import operator
>>> last = operator.itemgetter(-1)
>>> first = operator.itemgetter(0)

In either case:

>>> last(a_list)
'three'
>>> first(a_list)
'zero'

Special cases

If you're doing something more complicated, you may find it more performant to get the last element in slightly different ways.

If you're new to programming, you should avoid this section, because it couples otherwise semantically different parts of algorithms together. If you change your algorithm in one place, it may have an unintended impact on another line of code.

I try to provide caveats and conditions as completely as I can, but I may have missed something. Please comment if you think I'm leaving a caveat out.

Slicing

A slice of a list returns a new list - so we can slice from -1 to the end if we are going to want the element in a new list:

>>> a_slice = a_list[-1:]
>>> a_slice
['three']

This has the upside of not failing if the list is empty:

>>> empty_list = []
>>> tail = empty_list[-1:]
>>> if tail:
...     do_something(tail)

Whereas attempting to access by index raises an IndexError which would need to be handled:

>>> empty_list[-1]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range

But again, slicing for this purpose should only be done if you need:

  • a new list created
  • and the new list to be empty if the prior list was empty.

for loops

As a feature of Python, there is no inner scoping in a for loop.

If you're performing a complete iteration over the list already, the last element will still be referenced by the variable name assigned in the loop:

>>> def do_something(arg): pass
>>> for item in a_list:
...     do_something(item)
...     
>>> item
'three'

This is not semantically the last thing in the list. This is semantically the last thing that the name, item, was bound to.

>>> def do_something(arg): raise Exception
>>> for item in a_list:
...     do_something(item)
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 1, in do_something
Exception
>>> item
'zero'

Thus this should only be used to get the last element if you

  • are already looping, and
  • you know the loop will finish (not break or exit due to errors), otherwise it will point to the last element referenced by the loop.

Getting and removing it

We can also mutate our original list by removing and returning the last element:

>>> a_list.pop(-1)
'three'
>>> a_list
['zero', 'one', 'two']

But now the original list is modified.

(-1 is actually the default argument, so list.pop can be used without an index argument):

>>> a_list.pop()
'two'

Only do this if

  • you know the list has elements in it, or are prepared to handle the exception if it is empty, and
  • you do intend to remove the last element from the list, treating it like a stack.

These are valid use-cases, but not very common.

Saving the rest of the reverse for later:

I don't know why you'd do it, but for completeness, since reversed returns an iterator (which supports the iterator protocol) you can pass its result to next:

>>> next(reversed([1,2,3]))
3

So it's like doing the reverse of this:

>>> next(iter([1,2,3]))
1

But I can't think of a good reason to do this, unless you'll need the rest of the reverse iterator later, which would probably look more like this:

reverse_iterator = reversed([1,2,3])
last_element = next(reverse_iterator)

use_later = list(reverse_iterator)

and now:

>>> use_later
[2, 1]
>>> last_element
3

Excel formula to reference 'CELL TO THE LEFT'

I think this is the easiest answer.

Use a "Name" to reference the offset.

Say you want to sum a column (Column A) all the way to, but not including, the cell holding the summation (say Cell A100); do this:

(I assume you are using A1 referencing when creating the Name; R1C1 can subsequently be switched to)

  1. Click anywhere in the sheet not on the top row - say Cell D9
  2. Define a Named Range called, say "OneCellAbove", but overwrite the 'RefersTo' box with "=D8" (no quotes)
  3. Now, in Cell A100 you can use the formula
    =SUM(A1:OneCellAbove)

Android Studio: /dev/kvm device permission denied

I got this error after updating my ubuntu to 18.04.1. I just download new system image for emulator or you can say that download new emulator and it is worked for me.

scp via java

I use this SFTP API which has SCP called Zehon, it's great, so easy to use with a lot of sample code. Here is the site http://www.zehon.com

How to find memory leak in a C++ code/project?

Running "Valgrind" can:

1) Help Identify Memory Leaks - show you how many memory leaks you have, and point out to the lines in the code where the leaked memory was allocated.

2) Point out wrong attempts to free memory (e.g. improper call of delete)

Instructions for using "Valgrind"

1) Get valgrind here.

2) Compile your code with -g flag

3) In your shell run:

valgrind --leak-check=yes myprog arg1 arg2

Where "myprog" is your compiled program and arg1, arg2 your programme's arguments.

4) The result is a list of calls to malloc/new that did not have subsequent calls to free delete.

For example:

==4230==    at 0x1B977DD0: malloc (vg_replace_malloc.c:136)

==4230==    by 0x804990F: main (example.c:6)

Tells you in which line the malloc (that was not freed) was called.

As Pointed out by others, make sure that for every new/malloc call, you have a subsequent delete/free call.

What is the difference between user variables and system variables?

Environment variables are 'evaluated' (ie. they are attributed) in the following order:

  1. System variables
  2. Variables defined in autoexec.bat
  3. User variables

Every process has an environment block that contains a set of environment variables and their values. There are two types of environment variables: user environment variables (set for each user) and system environment variables (set for everyone). A child process inherits the environment variables of its parent process by default.

Programs started by the command processor inherit the command processor's environment variables.

Environment variables specify search paths for files, directories for temporary files, application-specific options, and other similar information. The system maintains an environment block for each user and one for the computer. The system environment block represents environment variables for all users of the particular computer. A user's environment block represents the environment variables the system maintains for that particular user, including the set of system environment variables.

how to reset <input type = "file">

The jQuery solution that @dhaval-marthak posted in the comments obviously works, but if you look at the actual jQuery call it's pretty easy to see what jQuery is doing, just setting the value attribute to an empty string. So in "pure" JavaScript it would be:

document.getElementById("uploadCaptureInputFile").value = "";

ImageView - have height match width?

The ImageView "scaleType" function may help you here.

This code will keep the aspect ratio and position the image at the top:

android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:scaleType="fitStart"

Here is a great post showing the possibilities and appearances from using scaleType.

ImageView scaleType samples

How do I get a value of a <span> using jQuery?

I think this should be a simple example:

$('#item1 span').text();

or

$('#item1 span').html();

Google Play Services Library update and missing symbol @integer/google_play_services_version

To anyone using gradle: don't include the project source, but instead download it using SDK Manager and add this line to dependencies:

compile 'com.google.android.gms:play-services:4.0.30'

How to run a shell script on a Unix console or Mac terminal?

To run a non-executable sh script, use:

sh myscript

To run a non-executable bash script, use:

bash myscript

To start an executable (which is any file with executable permission); you just specify it by its path:

/foo/bar
/bin/bar
./bar

To make a script executable, give it the necessary permission:

chmod +x bar
./bar

When a file is executable, the kernel is responsible for figuring out how to execte it. For non-binaries, this is done by looking at the first line of the file. It should contain a hashbang:

#! /usr/bin/env bash

The hashbang tells the kernel what program to run (in this case the command /usr/bin/env is ran with the argument bash). Then, the script is passed to the program (as second argument) along with all the arguments you gave the script as subsequent arguments.

That means every script that is executable should have a hashbang. If it doesn't, you're not telling the kernel what it is, and therefore the kernel doesn't know what program to use to interprete it. It could be bash, perl, python, sh, or something else. (In reality, the kernel will often use the user's default shell to interprete the file, which is very dangerous because it might not be the right interpreter at all or it might be able to parse some of it but with subtle behavioural differences such as is the case between sh and bash).

A note on /usr/bin/env

Most commonly, you'll see hash bangs like so:

#!/bin/bash

The result is that the kernel will run the program /bin/bash to interpret the script. Unfortunately, bash is not always shipped by default, and it is not always available in /bin. While on Linux machines it usually is, there are a range of other POSIX machines where bash ships in various locations, such as /usr/xpg/bin/bash or /usr/local/bin/bash.

To write a portable bash script, we can therefore not rely on hard-coding the location of the bash program. POSIX already has a mechanism for dealing with that: PATH. The idea is that you install your programs in one of the directories that are in PATH and the system should be able to find your program when you want to run it by name.

Sadly, you cannot just do this:

#!bash

The kernel won't (some might) do a PATH search for you. There is a program that can do a PATH search for you, though, it's called env. Luckily, nearly all systems have an env program installed in /usr/bin. So we start env using a hardcoded path, which then does a PATH search for bash and runs it so that it can interpret your script:

#!/usr/bin/env bash

This approach has one downside: According to POSIX, the hashbang can have one argument. In this case, we use bash as the argument to the env program. That means we have no space left to pass arguments to bash. So there's no way to convert something like #!/bin/bash -exu to this scheme. You'll have to put set -exu after the hashbang instead.

This approach also has another advantage: Some systems may ship with a /bin/bash, but the user may not like it, may find it's buggy or outdated, and may have installed his own bash somewhere else. This is often the case on OS X (Macs) where Apple ships an outdated /bin/bash and users install an up-to-date /usr/local/bin/bash using something like Homebrew. When you use the env approach which does a PATH search, you take the user's preference into account and use his preferred bash over the one his system shipped with.

Running an Excel macro via Python?

I would expect the error is to do with the macro you're calling, try the following bit of code:

Code

import os, os.path
import win32com.client

if os.path.exists("excelsheet.xlsm"):
    xl=win32com.client.Dispatch("Excel.Application")
    xl.Workbooks.Open(os.path.abspath("excelsheet.xlsm"), ReadOnly=1)
    xl.Application.Run("excelsheet.xlsm!modulename.macroname")
##    xl.Application.Save() # if you want to save then uncomment this line and change delete the ", ReadOnly=1" part from the open function.
    xl.Application.Quit() # Comment this out if your excel script closes
    del xl

Disable asp.net button after click to prevent double clicking

Just need to add 2 attributes for asp button :

OnClientClick="this.disabled='true';"  UseSubmitBehavior="false"

e.g.

<asp:Button ID="Button1" runat="server" Text="TEST" OnClientClick="this.disabled='true';"  UseSubmitBehavior="false" CssClass="button-content btnwidth" OnClick="ServerSideMethod_Click"  />

For more details:

https://bytes.com/topic/asp-net/answers/918280-disable-button-click-prevent-multiple-postbacks

Why do I need to override the equals and hashCode methods in Java?

In order to use our own class objects as keys in collections like HashMap, Hashtable etc.. , we should override both methods ( hashCode() and equals() ) by having an awareness on internal working of collection. Otherwise, it leads to wrong results which we are not expected.

CSS selector (id contains part of text)

<div id='element_123_wrapper_text'>My sample DIV</div>

The Operator ^ - Match elements that starts with given value

div[id^="element_123"] {

}

The Operator $ - Match elements that ends with given value

div[id$="wrapper_text"] {

}

The Operator * - Match elements that have an attribute containing a given value

div[id*="wrapper_text"] {

}

An unhandled exception was generated during the execution of the current web request

In my case, I created a new project and when I ran it the first time, it gave me the following error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

So my solution was to go to the Package Manager Console inside the Visual Studio and run:Update-Package

Problem solved!!

HTML5 Email Validation

The input type=email page of the www.w3.org site notes that an email address is any string which matches the following regular expression:

/^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/

Use the required attribute and a pattern attribute to require the value to match the regex pattern.

<input
    type="text"
    pattern="/^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/"
    required
>

How do I run a Python script from C#?

I am having problems with stdin/stout - when payload size exceeds several kilobytes it hangs. I need to call Python functions not only with some short arguments, but with a custom payload that could be big.

A while ago, I wrote a virtual actor library that allows to distribute task on different machines via Redis. To call Python code, I added functionality to listen for messages from Python, process them and return results back to .NET. Here is a brief description of how it works.

It works on a single machine as well, but requires a Redis instance. Redis adds some reliability guarantees - payload is stored until a worked acknowledges completion. If a worked dies, the payload is returned to a job queue and then is reprocessed by another worker.

Return date as ddmmyyyy in SQL Server

Try following query to format datetime in sql server

FORMAT (frr.valid_from , 'dd/MM/yyyy hh:mm:ss')

get client time zone from browser

Often when people are looking for "timezones", what will suffice is just "UTC offset". e.g., their server is in UTC+5 and they want to know that their client is running in UTC-8.


In plain old javascript (new Date()).getTimezoneOffset()/60 will return the current number of hours offset from UTC.

It's worth noting a possible "gotcha" in the sign of the getTimezoneOffset() return value (from MDN docs):

The time-zone offset is the difference, in minutes, between UTC and local time. Note that this means that the offset is positive if the local timezone is behind UTC and negative if it is ahead. For example, for time zone UTC+10:00 (Australian Eastern Standard Time, Vladivostok Time, Chamorro Standard Time), -600 will be returned.


However, I recommend you use the day.js for time/date related Javascript code. In which case you can get an ISO 8601 formatted UTC offset by running:

> dayjs().format("Z")
"-08:00"

It probably bears mentioning that the client can easily falsify this information.

(Note: this answer originally recommended https://momentjs.com/, but dayjs is a more modern, smaller alternative.)

How to get current route

for new router >= RC.3

Best and a simple way to do this is!

import { Router } from '@angular/router';
constructor(router: Router) { 
      router.events.subscribe((url:any) => console.log(url));
      console.log(router.url);  // to print only path eg:"/login"
}

What is the python keyword "with" used for?

In python the with keyword is used when working with unmanaged resources (like file streams). It is similar to the using statement in VB.NET and C#. It allows you to ensure that a resource is "cleaned up" when the code that uses it finishes running, even if exceptions are thrown. It provides 'syntactic sugar' for try/finally blocks.

From Python Docs:

The with statement clarifies code that previously would use try...finally blocks to ensure that clean-up code is executed. In this section, I’ll discuss the statement as it will commonly be used. In the next section, I’ll examine the implementation details and show how to write objects for use with this statement.

The with statement is a control-flow structure whose basic structure is:

with expression [as variable]:
    with-block

The expression is evaluated, and it should result in an object that supports the context management protocol (that is, has __enter__() and __exit__() methods).

Update fixed VB callout per Scott Wisniewski's comment. I was indeed confusing with with using.

ObjectiveC Parse Integer from String

I really don't know what was so hard about this question, but I managed to do it this way:

[myStringContainingInt intValue];

It should be noted that you can also do:

myStringContainingInt.intValue;

How can I create a simple message box in Python?

You can use pyautogui or pymsgbox:

import pyautogui
pyautogui.alert("This is a message box",title="Hello World")

Using pymsgbox is the same as using pyautogui:

import pymsgbox
pymsgbox.alert("This is a message box",title="Hello World")

What is the default value for enum variable?

You can use this snippet :-D

using System;
using System.Reflection;

public static class EnumUtils
{
    public static T GetDefaultValue<T>()
        where T : struct, Enum
    {
        return (T)GetDefaultValue(typeof(T));
    }

    public static object GetDefaultValue(Type enumType)
    {
        var attribute = enumType.GetCustomAttribute<DefaultValueAttribute>(inherit: false);
        if (attribute != null)
            return attribute.Value;

        var innerType = enumType.GetEnumUnderlyingType();
        var zero = Activator.CreateInstance(innerType);
        if (enumType.IsEnumDefined(zero))
            return zero;

        var values = enumType.GetEnumValues();
        return values.GetValue(0);
    }
}

Example:

using System;

public enum Enum1
{
    Foo,
    Bar,
    Baz,
    Quux
}
public enum Enum2
{
    Foo  = 1,
    Bar  = 2,
    Baz  = 3,
    Quux = 0
}
public enum Enum3
{
    Foo  = 1,
    Bar  = 2,
    Baz  = 3,
    Quux = 4
}
[DefaultValue(Enum4.Bar)]
public enum Enum4
{
    Foo  = 1,
    Bar  = 2,
    Baz  = 3,
    Quux = 4
}

public static class Program 
{
    public static void Main() 
    {
        var defaultValue1 = EnumUtils.GetDefaultValue<Enum1>();
        Console.WriteLine(defaultValue1); // Foo

        var defaultValue2 = EnumUtils.GetDefaultValue<Enum2>();
        Console.WriteLine(defaultValue2); // Quux

        var defaultValue3 = EnumUtils.GetDefaultValue<Enum3>();
        Console.WriteLine(defaultValue3); // Foo

        var defaultValue4 = EnumUtils.GetDefaultValue<Enum4>();
        Console.WriteLine(defaultValue4); // Bar
    }
}

Create Table from View

SELECT * INTO [table_a] FROM dbo.myView

insert password into database in md5 format?

You can use MD5() in mysql or md5() in php. To use salt add it to password before running md5, f.e.:

$salt ='my_string';
$hash = md5($salt . $password);

It's better to use different salt for every password. For this you have to save your salt in db (and also hash). While authentication user will send his login and pass. You will find his hash and salt in db and find out:

if ($hash == md5($salt . $_POST['password'])) {}

Can I serve multiple clients using just Flask app.run() as standalone?

Tips from 2020:

From Flask 1.0, it defaults to enable multiple threads (source), you don't need to do anything, just upgrade it with:

$ pip install -U flask

If you are using flask run instead of app.run() with older versions, you can control the threaded behavior with a command option (--with-threads/--without-threads):

$ flask run --with-threads

It's same as app.run(threaded=True)

How to convert an array to object in PHP?

Code

This function works as same as json_decode(json_encode($arr), false).

function arrayToObject(array $arr)
{
    $flat = array_keys($arr) === range(0, count($arr) - 1);
    $out = $flat ? [] : new \stdClass();

    foreach ($arr as $key => $value) {
        $temp = is_array($value) ? $this->arrayToObject($value) : $value;

        if ($flat) {
            $out[] = $temp;
        } else {
            $out->{$key} = $temp;
        }
    }

    return $out;
}

Testing

Test 1: Flat array

$arr = ["a", "b", "c"];
var_export(json_decode(json_encode($arr)));
var_export($this->arrayToObject($arr));

Output:

array(
    0 => 'a',
    1 => 'b',
    2 => 'c',
)
array(
    0 => 'a',
    1 => 'b',
    2 => 'c',
)

Test 2: Array of objects

$arr = [["a" => 1], ["a" => 1], ["a" => 1]];
var_export(json_decode(json_encode($arr)));
var_export($this->arrayToObject($arr));

Output:

array(
    0 => stdClass::__set_state(array('a' => 1,)),
    1 => stdClass::__set_state(array('a' => 1,)),
    2 => stdClass::__set_state(array('a' => 1,)),
)
array(
    0 => stdClass::__set_state(array('a' => 1,)),
    1 => stdClass::__set_state(array('a' => 1,)),
    2 => stdClass::__set_state(array('a' => 1,)),
)

Test 3: Object

$arr = ["a" => 1];
var_export(json_decode($arr));
var_export($this->arrayToObject($arr));

Output:

stdClass::__set_state(array('a' => 1,))
stdClass::__set_state(array('a' => 1,))

Elastic Search: how to see the indexed data

Kibana is also a good solution. It is a data visualization platform for Elastic.If installed it runs by default on port 5601.

Out of the many things it provides. It has "Dev Tools" where we can do your debugging.

For example you can check your available indexes here using the command

GET /_cat/indices

How can I compare strings in C using a `switch` statement?

We cannot escape if-else ladder in order to compare a string with others. Even regular switch-case is also an if-else ladder (for integers) internally. We might only want to simulate the switch-case for string, but can never replace if-else ladder. The best of the algorithms for string comparison cannot escape from using strcmp function. Means to compare character by character until an unmatch is found. So using if-else ladder and strcmp are inevitable.

DEMO

And here are simplest macros to simulate the switch-case for strings.

#ifndef SWITCH_CASE_INIT
#define SWITCH_CASE_INIT
    #define SWITCH(X)   for (char* __switch_p__ = X, int __switch_next__=1 ; __switch_p__ ; __switch_p__=0, __switch_next__=1) { {
    #define CASE(X)         } if (!__switch_next__ || !(__switch_next__ = strcmp(__switch_p__, X))) {
    #define DEFAULT         } {
    #define END         }}
#endif

And you can use them as

char* str = "def";

SWITCH (str)
    CASE ("abc")
        printf ("in abc\n");
        break;
    CASE ("def")              // Notice: 'break;' statement missing so the control rolls through subsequent CASE's until DEFAULT 
        printf("in def\n");
    CASE ("ghi")
        printf ("in ghi\n");
    DEFAULT
        printf("in DEFAULT\n");
END

Output:

in def
in ghi
in DEFAULT

Below is nested SWITCH usage:

char* str = "def";
char* str1 = "xyz";

SWITCH (str)
    CASE ("abc")
        printf ("in abc\n");
        break;
    CASE ("def")                                
        printf("in def\n");
        SWITCH (str1)                           // <== Notice: Nested SWITCH
            CASE ("uvw")
                printf("in def => uvw\n");
                break;
            CASE ("xyz")
                printf("in def => xyz\n");
                break;
            DEFAULT
                printf("in def => DEFAULT\n");
        END
    CASE ("ghi")
        printf ("in ghi\n");
    DEFAULT
        printf("in DEFAULT\n");
END

Output:

in def
in def => xyz
in ghi
in DEFAULT

Here is reverse string SWITCH, where in you can use a variable (rather than a constant) in CASE clause:

char* str2 = "def";
char* str3 = "ghi";

SWITCH ("ghi")                      // <== Notice: Use of variables and reverse string SWITCH.
    CASE (str1)
        printf ("in str1\n");
        break;
    CASE (str2)                     
        printf ("in str2\n");
        break;
    CASE (str3)                     
        printf ("in str3\n");
        break;
    DEFAULT
        printf("in DEFAULT\n");
END

Output:

in str3

HTTP Content-Type Header and JSON

Recently ran into a problem with this and a Chrome extension that was corrupting a JSON stream when the response header labeled the content-type as 'text/html' apparently extensions can and will use the response header to alter the content prior to further processing by the browser. Changing the content-type fixed the issue.

How can I count the number of elements with same class?

$('#maindivid').find('input .inputclass').length

accessing a file using [NSBundle mainBundle] pathForResource: ofType:inDirectory:

All you need to do is make sure that the checkbox shown below is checked.

enter image description here

Fast way of finding lines in one file that are not in another?

$ join -v 1 -t '' file1 file2
line2
line3

The -t makes sure that it compares the whole line, if you had a space in some of the lines.

SQL Server : login success but "The database [dbName] is not accessible. (ObjectExplorer)"

I had twoo users: one that had the sysadmin role, the other one (the problematic one) didn't.

So I logged in with the other user(you can create a new one) and checked the ckeck box 'sysadmin' from: Security --> Logins --> Right ckick on your SQL user name --> Properties --> Server Roles --> make sure that the 'sysadmin' checkbox has the check mark. Press OK and try connecting with the newly checked user.

JavaScript post request like a form submit

The Prototype library includes a Hashtable object, with a ".toQueryString()" method, which allows you to easily turn a JavaScript object/structure into a query-string style string. Since the post requires the "body" of the request to be a query-string formatted string, this allows your Ajax request to work properly as a post. Here's an example using Prototype:

$req = new Ajax.Request("http://foo.com/bar.php",{
    method: 'post',
    parameters: $H({
        name: 'Diodeus',
        question: 'JavaScript posts a request like a form request',
        ...
    }).toQueryString();
};

How to access JSON Object name/value?

Try this code..

function (data) {


var json = jQuery.parseJSON(data);
alert( json.name );


}

Explicit vs implicit SQL joins

Basically, the difference between the two is that one is written in the old way, while the other is written in the modern way. Personally, I prefer the modern script using the inner, left, outer, right definitions because they are more explanatory and makes the code more readable.

When dealing with inner joins there is no real difference in readability neither, however, it may get complicated when dealing with left and right joins as in the older method you would get something like this:

SELECT * 
FROM table a, table b
WHERE a.id = b.id (+);

The above is the old way how a left join is written as opposed to the following:

SELECT * 
FROM table a 
LEFT JOIN table b ON a.id = b.id;

As you can visually see, the modern way of how the script is written makes the query more readable. (By the way same goes for right joins and a little more complicated for outer joins).

Going back to the boiler plate, it doesn't make a difference to the SQL compiler how the query is written as it handles them in the same way. I've seen a mix of both in Oracle databases which have had many people writing into it, both elder and younger ones. Again, it boils down to how readable the script is and the team you are developing with.

Static extension methods

In short, no, you can't.

Long answer, extension methods are just syntactic sugar. IE:

If you have an extension method on string let's say:

public static string SomeStringExtension(this string s)
{
   //whatever..
}

When you then call it:

myString.SomeStringExtension();

The compiler just turns it into:

ExtensionClass.SomeStringExtension(myString);

So as you can see, there's no way to do that for static methods.

And another thing just dawned on me: what would really be the point of being able to add static methods on existing classes? You can just have your own helper class that does the same thing, so what's really the benefit in being able to do:

Bool.Parse(..)

vs.

Helper.ParseBool(..);

Doesn't really bring much to the table...

How to run TypeScript files from command line?

  1. Install ts-node node module globally.
  2. Create node runtime configuration (for IDE) or use node in command line to run below file js file (The path is for windows, but you can do it for linux as well) ~\AppData\Roaming\npm\node_modules\ts-node\dist\bin.js
  3. Give your ts file path as a command line argument.
  4. Run Or Debug as you like.

Angular.js ng-repeat filter by property having one of multiple values (OR of values)

After not able to find a good universal solution I made something of my own. I have not tested it for a very large list.

It takes care of nested keys,arrays or just about anything.

Here is the github and demo

app.filter('xf', function() {
    function keyfind(f, obj) {
        if (obj === undefined)
            return -1;
        else {
            var sf = f.split(".");
            if (sf.length <= 1) {
                return obj[sf[0]];
            } else {
                var newobj = obj[sf[0]];
                sf.splice(0, 1);
                return keyfind(sf.join("."), newobj)
            }
        }

    }
    return function(input, clause, fields) {
        var out = [];
        if (clause && clause.query && clause.query.length > 0) {
            clause.query = String(clause.query).toLowerCase();
            angular.forEach(input, function(cp) {
                for (var i = 0; i < fields.length; i++) {
                    var haystack = String(keyfind(fields[i], cp)).toLowerCase();
                    if (haystack.indexOf(clause.query) > -1) {
                        out.push(cp);
                        break;
                    }
                }
            })
        } else {
            angular.forEach(input, function(cp) {
                out.push(cp);
            })
        }
        return out;
    }

})

HTML

<input ng-model="search.query" type="text" placeholder="search by any property">
<div ng-repeat="product in products |  xf:search:['color','name']">
...
</div>

How can I select all options of multi-select select box on click?

Give selected attribute to all options like this

$('#countries option').attr('selected', 'selected');

Usage:

$('#select_all').click( function() {
    $('#countries option').attr('selected', 'selected');
});

Update

In case you are using 1.6+, better option would be to use .prop() instead of .attr()

$('#select_all').click( function() {
    $('#countries option').prop('selected', true);
});

adding classpath in linux

Paths under linux are separated by colons (:), not semi-colons (;), as theatrus correctly used it in his example. I believe Java respects this convention.

Edit

Alternatively to what andy suggested, you may use the following form (which sets CLASSPATH for the duration of the command):

CLASSPATH=".:../somejar.jar:../mysql-connector-java-5.1.6-bin.jar" java -Xmx500m ...

whichever is more convenient to you.

Best Practices for mapping one object to another

Efran Cobisi's suggestion of using an Auto Mapper is a good one. I have used Auto Mapper for a while and it worked well, until I found the much faster alternative, Mapster.

Given a large list or IEnumerable, Mapster outperforms Auto Mapper. I found a benchmark somewhere that showed Mapster being 6 times as fast, but I could not find it again. You could look it up and then, if it is suits you, use Mapster.

LINQ Group By and select collection

you may also like this

var Grp = Model.GroupBy(item => item.Order.Customer)
      .Select(group => new 
        { 
             Customer = Model.First().Customer, 
             CustomerId= group.Key,  
             Orders= group.ToList() 
       })
      .ToList();

How to delete a cookie?

You can do this by setting the date of expiry to yesterday.

Setting it to "-1" doesn't work. That marks a cookie as a Sessioncookie.

Does List<T> guarantee insertion order?

Here are 4 items, with their index

0  1  2  3
K  C  A  E

You want to move K to between A and E -- you might think position 3. You have be careful about your indexing here, because after the remove, all the indexes get updated.

So you remove item 0 first, leaving

0  1  2
C  A  E

Then you insert at 3

0  1  2  3
C  A  E  K

To get the correct result, you should have used index 2. To make things consistent, you will need to send to (indexToMoveTo-1) if indexToMoveTo > indexToMove, e.g.

bool moveUp = (listInstance.IndexOf(itemToMoveTo) > indexToMove);
listInstance.Remove(itemToMove);
listInstance.Insert(indexToMoveTo, moveUp ? (itemToMoveTo - 1) : itemToMoveTo);

This may be related to your problem. Note my code is untested!

EDIT: Alternatively, you could Sort with a custom comparer (IComparer) if that's applicable to your situation.

Can enums be subclassed to add new elements?

I suggest you take the other way around approach.

Instead of extending the existing enumeration, create a larger one and create a subset of it. For exemple if you had an enumeration called PET and you wanted to extend it to ANIMAL you should do this instead:

public enum ANIMAL {
    WOLF,CAT, DOG
} 
EnumSet<ANIMAL> pets = EnumSet.of(ANIMAL.CAT, ANIMAL.DOG);

Be careful, pets is not an immutable collections, you might want to use Guava or Java9 for more safety.

Filename too long in Git for Windows

Git has a limit of 4096 characters for a filename, except on Windows when Git is compiled with msys. It uses an older version of the Windows API and there's a limit of 260 characters for a filename.

So as far as I understand this, it's a limitation of msys and not of Git. You can read the details here: https://github.com/msysgit/git/pull/110

You can circumvent this by using another Git client on Windows or set core.longpaths to true as explained in other answers.

git config --system core.longpaths true

Git is build as a combination of scripts and compiled code. With the above change some of the scripts might fail. That's the reason for core.longpaths not to be enabled by default.

The windows documentation at https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file has some more information:

Starting in Windows 10, version 1607, MAX_PATH limitations have been removed from common Win32 file and directory functions. However, you must opt-in to the new behavior.

A registry key allows you to enable or disable the new long path behavior. To enable long path behavior set the registry key at HKLM\SYSTEM\CurrentControlSet\Control\FileSystem LongPathsEnabled (Type: REG_DWORD)

Get the first item from an iterable that matches a condition

This question already has great answers. I'm only adding my two cents because I landed here trying to find a solution to my own problem, which is very similar to the OP.

If you want to find the INDEX of the first item matching a criteria using generators, you can simply do:

next(index for index, value in enumerate(iterable) if condition)

invalid use of non-static member function

You shall pass a this pointer to tell the function which object to work on because it relies on that as opposed to a static member function.

ssh "permissions are too open" error

Putty can do the work on windows 10. It generates a public key using a private key as input.

  1. download putty from https://www.putty.org/
  2. install putty. Two applications come upon the installation: putty config, putty key gen
  3. launch puttyGen
  4. click load and select a private key file. Please note, you need to rename your private key file with .ppk extension,e.g private-key.ppk enter image description here

Get IFrame's document, from JavaScript in main document

In case you get a cross-domain error:

If you have control over the content of the iframe - that is, if it is merely loaded in a cross-origin setup such as on Amazon Mechanical Turk - you can circumvent this problem with the <body onload='my_func(my_arg)'> attribute for the inner html.

For example, for the inner html, use the this html parameter (yes - this is defined and it refers to the parent window of the inner body element):

<body onload='changeForm(this)'>

In the inner html :

    function changeForm(window) {
        console.log('inner window loaded: do whatever you want with the inner html');
        window.document.getElementById('mturk_form').style.display = 'none';
    </script>

Wait some seconds without blocking UI execution

i really disadvise you against using Thread.Sleep(2000), because of a several reasons (a few are described here), but most of all because its not useful when it comes to debugging/testing.

I recommend to use a C# Timer instead of Thread.Sleep(). Timers let you perform methods frequently (if necessary) AND are much easiert to use in testing! There's a very nice example of how to use a timer right behind the hyperlink - just put your logic "what happens after 2 seconds" right into the Timer.Elapsed += new ElapsedEventHandler(OnTimedEvent); method.

Hide "NFC Tag type not supported" error on Samsung Galaxy devices

Before Android 4.4

What you are trying to do is simply not possible from an app (at least not on a non-rooted/non-modified device). The message "NFC tag type not supported" is displayed by the Android system (or more specifically the NFC system service) before and instead of dispatching the tag to your app. This means that the NFC system service filters MIFARE Classic tags and never notifies any app about them. Consequently, your app can't detect MIFARE Classic tags or circumvent that popup message.

On a rooted device, you may be able to bypass the message using either

  1. Xposed to modify the behavior of the NFC service, or
  2. the CSC (Consumer Software Customization) feature configuration files on the system partition (see /system/csc/. The NFC system service disables the popup and dispatches MIFARE Classic tags to apps if the CSC feature <CscFeature_NFC_EnableSecurityPromptPopup> is set to any value but "mifareclassic" or "all". For instance, you could use:

    <CscFeature_NFC_EnableSecurityPromptPopup>NONE</CscFeature_NFC_EnableSecurityPromptPopup>
    

    You could add this entry to, for instance, the file "/system/csc/others.xml" (within the section <FeatureSet> ... </FeatureSet> that already exists in that file).

Since, you asked for the Galaxy S6 (the question that you linked) as well: I have tested this method on the S4 when it came out. I have not verified if this still works in the latest firmware or on other devices (e.g. the S6).

Since Android 4.4

This is pure guessing, but according to this (link no longer available), it seems that some apps (e.g. NXP TagInfo) are capable of detecting MIFARE Classic tags on affected Samsung devices since Android 4.4. This might mean that foreground apps are capable of bypassing that popup using the reader-mode API (see NfcAdapter.enableReaderMode) possibly in combination with NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK.

How to add Options Menu to Fragment in Android

TL;DR

Use the android.support.v7.widget.Toolbar and just do:

toolbar.inflateMenu(R.menu.my_menu)
toolbar.setOnMenuItemClickListener {
    onOptionsItemSelected(it)
}

Standalone Toolbar

Most of the suggested solutions like setHasOptionsMenu(true) are only working when the parent Activity has the Toolbar in its layout and declares it via setSupportActionBar(). Then the Fragments can participate in the menu population of this exact ActionBar:

Fragment.onCreateOptionsMenu(): Initialize the contents of the Fragment host's standard options menu.

If you want a standalone toolbar and menu for one specific Fragment you can to do the following:

menu_custom_fragment.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/menu_save"
        android:title="SAVE" />
</menu>

custom_fragment.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    ...

CustomFragment.kt

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    val view = inflater.inflate(layout.custom_fragment, container, false)
    val toolbar = view.findViewById<Toolbar>(R.id.toolbar)
    toolbar.inflateMenu(R.menu.menu_custom_fragment)
    toolbar.setOnMenuItemClickListener {
        onOptionsItemSelected(it)
    }
    return view
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return when (item.itemId) {
        R.id.menu_save -> {
            // TODO: User clicked the save button
            true
        }
        else -> super.onOptionsItemSelected(item)
    }
}

Yes, it's that easy. You don't even need to override onCreate() or onCreateOptionsMenu().

PS: This is only working with android.support.v4.app.Fragment and android.support.v7.widget.Toolbar (also be sure to use AppCompatActivity and an AppCompat theme in your styles.xml).

How to read lines of a file in Ruby

Your first file has Mac Classic line endings (that’s "\r" instead of the usual "\n"). Open it with

File.open('foo').each(sep="\r") do |line|

to specify the line endings.

How to open a new HTML page using jQuery?

You need to use ajax.

http://api.jquery.com/jQuery.ajax/

<code>
$.ajax({
  url: 'ajax/test.html',
  success: function(data) {
    $('.result').html(data);
    alert('Load was performed.');
  }
});
</code>

How to check empty object in angular 2 template using *ngIf

From the above answeres, following did not work or less preferable:

  • (previous_info | json) != '{}' works only for {} empty case, not for null or undefined case
  • Object.getOwnPropertyNames(previous_info).length also did not work, as Object is not accessible in the template
  • I would not like to create a dedicated variable this.objectLength = Object.keys(this.previous_info).length !=0;
  • I would not like to create a dedicated function

    isEmptyObject(obj) {
       return (obj && (Object.keys(obj).length === 0));
    }
    

Solution: keyvalue pipe along with ?. (safe navigation operator); and it seems simple.

It works well when previous_info = null or previous_info = undefined or previous_info = {} and treats as falsy value.

<div  *ngIf="(previous_info | keyvalue)?.length">

keyvalue - Transforms Object or Map into an array of key value pairs.

?. - The Angular safe navigation operator (?.) is a fluent and convenient way to guard against null and undefined

DEMO: demo with angular 9, though it works for previous versions as well

AngularJS ng-class if-else expression

You can try this method:

</p><br /><br />
<p>ng-class="{test: obj.value1 == 'someothervalue' || obj.value2 == 'somethingelse'}<br /><br /><br />

ng-class="{test: obj.value1 == 'someothervalue' || obj.value2 == 'somethingelse'}

You can get complete details from here.

jquery clone div and append it after specific div

You can use clone, and then since each div has a class of car_well you can use insertAfter to insert after the last div.

$("#car2").clone().insertAfter("div.car_well:last");

How to convert char to integer in C?

In the old days, when we could assume that most computers used ASCII, we would just do

int i = c[0] - '0';

But in these days of Unicode, it's not a good idea. It was never a good idea if your code had to run on a non-ASCII computer.

Edit: Although it looks hackish, evidently it is guaranteed by the standard to work. Thanks @Earwicker.

How do I check if a string contains another string in Swift?

Swift 4 way to check for substrings, including the necessary Foundation (or UIKit) framework import:

import Foundation // or UIKit

let str = "Oh Canada!"

str.contains("Can") // returns true

str.contains("can") // returns false

str.lowercased().contains("can") // case-insensitive, returns true

Unless Foundation (or UIKit) framework is imported, str.contains("Can") will give a compiler error.


This answer is regurgitating manojlds's answer, which is completely correct. I have no idea why so many answers go through so much trouble to recreate Foundation's String.contains(subString: String) method.

nodejs send html file to client

After years, I want to add another approach by using a view engine in Express.js

var fs = require('fs');

app.get('/test', function(req, res, next) {
    var html = fs.readFileSync('./html/test.html', 'utf8')
    res.render('test', { html: html })
    // or res.send(html)
})

Then, do that in your views/test if you choose res.render method at the above code (I'm writing in EJS format):

<%- locals.html %>

That's all.

In this way, you don't need to break your View Engine arrangements.

MySQL set current date in a DATETIME field on insert

DELIMITER ;;
CREATE TRIGGER `my_table_bi` BEFORE INSERT ON `my_table` FOR EACH ROW
BEGIN
    SET NEW.created_date = NOW();
END;;
DELIMITER ;

Convert js Array() to JSon object for use with JQuery .ajax

If the array is already defined, you can create a json object by looping through the elements of the array which you can then post to the server, but if you are creating the array as for the case above, just create a json object instead as sugested by Paolo Bergantino

    var saveData = Array();
    saveData["a"] = 2;
    saveData["c"] = 1;
    
    //creating a json object
    var jObject={};
    for(i in saveData)
    {
        jObject[i] = saveData[i];
    }

    //Stringify this object and send it to the server
    
    jObject= YAHOO.lang.JSON.stringify(jObject);
    $.ajax({
            type:'post',
           cache:false,
             url:"salvaPreventivo.php",
            data:{jObject:  jObject}
    });
    
    // reading the data at the server
    <?php
    $data = json_decode($_POST['jObject'], true);
    print_r($data);
    ?>

    //for jObject= YAHOO.lang.JSON.stringify(jObject); to work,
    //include the follwing files

    //<!-- Dependencies -->
    //<script src="http://yui.yahooapis.com/2.9.0/build/yahoo/yahoo-min.js"></script>

    //<!-- Source file -->
    //<script src="http://yui.yahooapis.com/2.9.0/build/json/json-min.js"></script>

Hope this helps

Expected response code 250 but got code "530", with message "530 5.7.1 Authentication required

Yep, and if you have tried all the above solutions (what's more likely to happen) and none work for you, it may happen that Guzzle is not installed.

Laravel ships mailing tools, by which is required the Guzzle framework, but it won't be installed, and AS OF the documentation, will have to install it manually: https://laravel.com/docs/master/mail#driver-prerequisites

composer require guzzlehttp/guzzle

How do I clear my local working directory in Git?

All the answers so far retain local commits. If you're really serious, you can discard all local commits and all local edits by doing:

git reset --hard origin/branchname

For example:

git reset --hard origin/master

This makes your local repository exactly match the state of the origin (other than untracked files).

If you accidentally did this after just reading the command, and not what it does :), use git reflog to find your old commits.

Change input value onclick button - pure javascript or jQuery

My Attempt ( JsFiddle)

Javascript

$(document).ready(function () {
    $('#buttons input[type=button]').on('click', function () {
        var qty = $(this).data('quantity');
        var price = $('#totalPrice').text(); 
        $('#count').val(price * qty);
    });
});

Html

  Product price:$500
<br>Total price: $<span id='totalPrice'>500</span>
<br>
<div id='buttons'>
    <input id='qty2' type="button" data-quantity='2' value="2&#x00A;Qty">
    <input id='qty2' type="button" class="mnozstvi_sleva" data-quantity='4' value="4&#x00A;Qty">
</div>
<br>Total
<input type="text" id="count" value="1">

Encoding Javascript Object to Json string

You can use JSON.stringify like:

JSON.stringify(new_tweets);

Kill a postgresql session/connection

Definitely one of the answers above gave me the idea for solving it in Windows.

Open the Services from Windows, locate the Postgres service and restart it.

What is the difference between Jupyter Notebook and JupyterLab?

This answer shows the python perspective. Jupyter supports various languages besides python.

Both Jupyter Notebook and Jupyterlab are browser compatible interactive python (i.e. python ".ipynb" files) environments, where you can divide the various portions of the code into various individually executable cells for the sake of better readability. Both of these are popular in Data Science/Scientific Computing domain.

I'd suggest you to go with Jupyterlab for the advantages over Jupyter notebooks:

  1. In Jupyterlab, you can create ".py" files, ".ipynb" files, open terminal etc. Jupyter Notebook allows ".ipynb" files while providing you the choice to choose "python 2" or "python 3".
  2. Jupyterlab can open multiple ".ipynb" files inside a single browser tab. Whereas, Jupyter Notebook will create new tab to open new ".ipynb" files every time. Hovering between various tabs of browser is tedious, thus Jupyterlab is more helpful here.

I'd recommend using PIP to install Jupyterlab.

If you can't open a ".ipynb" file using Jupyterlab on Windows system, here are the steps:

  1. Go to the file --> Right click --> Open With --> Choose another app --> More Apps --> Look for another apps on this PC --> Click.
  2. This will open a file explorer window. Now go inside your Python installation folder. You should see Scripts folder. Go inside it.
  3. Once you find jupyter-lab.exe, select that and now it will open the .ipynb files by default on your PC.

Javascript Get Values from Multiple Select Option Box

The for loop is getting one extra run. Change

for (x=0;x<=InvForm.SelBranch.length;x++)

to

for (x=0; x < InvForm.SelBranch.length; x++)

Annotations from javax.validation.constraints not working

in my case i had a custom class-level constraint that was not being called.

@CustomValidation // not called
public class MyClass {
    @Lob
    @Column(nullable = false)
    private String name;
}

as soon as i added a field-level constraint to my class, either custom or standard, the class-level constraint started working.

@CustomValidation // now it works. super.
public class MyClass {
    @Lob
    @Column(nullable = false)
    @NotBlank // adding this made @CustomValidation start working
    private String name;
}

seems like buggy behavior to me but easy enough to work around i guess

Sorting string array in C#

This code snippet is working properly enter image description here

Add Foreign Key relationship between two Databases

You would need to manage the referential constraint across databases using a Trigger.


Basically you create an insert, update trigger to verify the existence of the Key in the Primary key table. If the key does not exist then revert the insert or update and then handle the exception.

Example:

Create Trigger dbo.MyTableTrigger ON dbo.MyTable, After Insert, Update
As
Begin

   If NOT Exists(select PK from OtherDB.dbo.TableName where PK in (Select FK from inserted) BEGIN
      -- Handle the Referential Error Here
   END

END

Edited: Just to clarify. This is not the best approach with enforcing referential integrity. Ideally you would want both tables in the same db but if that is not possible. Then the above is a potential work around for you.

How to connect to SQL Server from command prompt with Windows authentication

You can use different syntax to achieve different things. If it is windows authentication you want, you could try this:

sqlcmd /S  /d  -E

If you want to use SQL Server authentication you could try this:

sqlcmd /S  /d -U -P 

Definitions:

/S = the servername/instance name. Example: Pete's Laptop/SQLSERV
/d = the database name. Example: Botlek1
-E = Windows authentication.
-U = SQL Server authentication/user. Example: Pete
-P = password that belongs to the user. Example: 1234

Hope this helps!

How do I compare strings in GoLang?

For the Platform Independent Users or Windows users, what you can do is:

import runtime:

import (
    "runtime"
    "strings"
)

and then trim the string like this:

if runtime.GOOS == "windows" {
  input = strings.TrimRight(input, "\r\n")
} else {
  input = strings.TrimRight(input, "\n")
}

now you can compare it like that:

if strings.Compare(input, "a") == 0 {
  //....yourCode
}

This is a better approach when you're making use of STDIN on multiple platforms.

Explanation

This happens because on windows lines end with "\r\n" which is known as CRLF, but on UNIX lines end with "\n" which is known as LF and that's why we trim "\n" on unix based operating systems while we trim "\r\n" on windows.

referenced before assignment error in python

My Scenario

def example():
    cl = [0, 1]
    def inner():
        #cl = [1, 2] # access this way will throw `reference before assignment`
        cl[0] = 1 
        cl[1] = 2   # these won't

    inner()

Displaying better error message than "No JSON object could be decoded"

You wont be able to get python to tell you where the JSON is incorrect. You will need to use a linter online somewhere like this

This will show you error in the JSON you are trying to decode.

How to open a WPF Popup when another control is clicked, using XAML markup only?

another way to do it:

<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                    <StackPanel>
                        <Image Source="{Binding ProductImage,RelativeSource={RelativeSource TemplatedParent}}" Stretch="Fill" Width="65" Height="85"/>
                        <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                        <Button x:Name="myButton" Width="40" Height="10">
                            <Popup Width="100" Height="70" IsOpen="{Binding ElementName=myButton,Path=IsMouseOver, Mode=OneWay}">
                                <StackPanel Background="Yellow">
                                    <ItemsControl ItemsSource="{Binding Produkt.SubProducts}"/>
                                </StackPanel>
                            </Popup>
                        </Button>
                    </StackPanel>
                </Border>

How do I ignore all files in a folder with a Git repository in Sourcetree?

  • Ignore all files in folder with Git in Sourcetree:

Ignore all files in folder with Git in Sourcetree

Request header field Access-Control-Allow-Headers is not allowed by itself in preflight response

Very good i used this on a silex project

$app->after(function (Request $request, Response $response) {
        $response->headers->set('Access-Control-Allow-Origin', '*');
        $response->headers->set("Access-Control-Allow-Credentials", "true");
        $response->headers->set("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");
        $response->headers->set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Authorization");
    });

MySQL Query to select data from last week?

i Use this for the week start from SUNDAY:

SELECT id FROM tbl
WHERE
date >= curdate() - INTERVAL DAYOFWEEK(curdate())+5 DAY  
AND date < curdate() - INTERVAL DAYOFWEEK(curdate())-2 DAY

Do I commit the package-lock.json file created by npm 5?

Yes, you can commit this file. From the npm's official docs:

package-lock.json is automatically generated for any operations where npm modifies either the node_modules tree, or package.json. It describes the exact tree that was generated, such that subsequent installs are able to generate identical trees, regardless of intermediate dependency updates.

This file is intended to be committed into source repositories[.]

java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1888, result=0, data=null} to activity

Adding this first conditional should work:

protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
    if(resultCode != RESULT_CANCELED){
        if (requestCode == CAMERA_REQUEST) {  
            Bitmap photo = (Bitmap) data.getExtras().get("data"); 
            imageView.setImageBitmap(photo);
        }
    }
}

Please initialize the log4j system properly. While running web service

You have to create your own log4j.properties in the classpath folder.

Xcode stops working after set "xcode-select -switch"

You should be pointing it towards the Developer directory, not the Xcode application bundle. Run this:

sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer

With recent versions of Xcode, you can go to Xcode ? Preferences… ? Locations and pick one of the options for Command Line Tools to set the location.

Image resizing in React Native

This worked for me:

image: {
    flex: 1,
    aspectRatio: 1.5, 
    resizeMode: 'contain',

  }

aspectRatio is just width/height (my image is 45px wide x 30px high).

Load local HTML file in a C# WebBrowser

Windows 10 uwp application.

Try this:

webview.Navigate(new Uri("ms-appx-web:///index.html"));

How to dismiss the dialog with click on outside of the dialog?

Here is the code

    dialog.getWindow().getDecorView().setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent ev) {

            if(MotionEvent.ACTION_DOWN == ev.getAction())
            {
                Rect dialogBounds = new Rect();
                dialog. getWindow().getDecorView().getHitRect(dialogBounds);
                if (!dialogBounds.contains((int) ev.getX(), (int) ev.getY())) {
                    // You have clicked the grey area
                    UiUtils.hideKeyboard2(getActivity());
                    return false; // stop activity closing
                }
            }
            getActivity().dispatchTouchEvent(ev);
            return false;
        }
    });

Try this one . you can hide the keyboard when you touch outside

Importing .py files in Google Colab

Try this way:

I have a package named plant_seedlings. The package is stored in google drive. What I should do is to copy this package in /usr/local/lib/python3.6/dist-packages/.

!cp /content/drive/ai/plant_seedlings.tar.gz /usr/local/lib/python3.6/dist-packages/

!cd /usr/local/lib/python3.6/dist-packages/ && tar -xzf plant_seedlings.tar.gz

!cd /content

!python -m plant_seedlings

Bootstrap 3 modal responsive

From the docs:

Modals have two optional sizes, available via modifier classes to be placed on a .modal-dialog: modal-lg and modal-sm (as of 3.1).

Also the modal dialogue will scale itself on small screens (as of 3.1.1).

Convert DateTime to a specified Format

Easy peasy:

var date = DateTime.Parse("14/11/2011"); // may need some Culture help here
Console.Write(date.ToString("yyyy-MM-dd"));

Take a look at DateTime.ToString() method, Custom Date and Time Format Strings and Standard Date and Time Format Strings

string customFormattedDateTimeString = DateTime.Now.ToString("yyyy-MM-dd");

Java Comparator class to sort arrays

[...] How should Java Comparator class be declared to sort the arrays by their first elements in decreasing order [...]

Here's a complete example using Java 8:

import java.util.*;

public class Test {

    public static void main(String args[]) {

        int[][] twoDim = { {1, 2}, {3, 7}, {8, 9}, {4, 2}, {5, 3} };

        Arrays.sort(twoDim, Comparator.comparingInt(a -> a[0])
                                      .reversed());

        System.out.println(Arrays.deepToString(twoDim));
    }
}

Output:

[[8, 9], [5, 3], [4, 2], [3, 7], [1, 2]]

For Java 7 you can do:

Arrays.sort(twoDim, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return Integer.compare(o2[0], o1[0]);
    }
});

If you unfortunate enough to work on Java 6 or older, you'd do:

Arrays.sort(twoDim, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return ((Integer) o2[0]).compareTo(o1[0]);
    }
});

Android Studio: Drawable Folder: How to put Images for Multiple dpi?

New -> Batch Drawable Import -> Click on Add button -> Select image -> Select Target Resolution, Target Name, Format -> Ok

SVN "Already Locked Error"

I had the same problem: I can't commit a lot of files at once.


The commit works by:

  1. Running a "clean up" from Tortoise SVN

  2. Commit each file separate. Create new root folder and commit each file or folder.


** If the error returns you should repeat action no.1-2 **

Get first key in a (possibly) associative array?

I think the best and fastest way to do it is:

$first_key=key(array_slice($array, 0, 1, TRUE))

What is "stdafx.h" used for in Visual Studio?

"Stdafx.h" is a precompiled header.It include file for standard system include files and for project-specific include files that are used frequently but are changed infrequently.which reduces compile time and Unnecessary Processing.

Precompiled Header stdafx.h is basically used in Microsoft Visual Studio to let the compiler know the files that are once compiled and no need to compile it from scratch. You can read more about it

http://www.cplusplus.com/articles/1TUq5Di1/

https://docs.microsoft.com/en-us/cpp/ide/precompiled-header-files?view=vs-2017

How do I build a graphical user interface in C++?

OS independent algorithm "Creating GUI applications in C++ in three steps":

  1. Install Qt Creator

    enter image description here

  2. Create new project (Qt Widgets Application)

    enter image description here

  3. Build it.

Congratulations, you've got your first GUI in C++.

Now you're ready to read a lot of documentation to create something more complicate than "Hello world" GUI application.

Table row and column number in jQuery

You can use the Core/index function in a given context, for example you can check the index of the TD in it's parent TR to get the column number, and you can check the TR index on the Table, to get the row number:

$('td').click(function(){
  var col = $(this).parent().children().index($(this));
  var row = $(this).parent().parent().children().index($(this).parent());
  alert('Row: ' + row + ', Column: ' + col);
});

Check a running example here.

What is DOM element?

When a web page is loaded, the browser creates a Document Object Model of the page.

The HTML DOM model is constructed as a tree of Objects:

With the object model, JavaScript gets all the power it needs to create dynamic HTML:

  • JavaScript can change all the HTML elements in the page
  • JavaScript can change all the HTML attributes in the page
  • JavaScript can change all the CSS styles in the page
  • JavaScript can remove existing HTML elements and attributes
  • JavaScript can add new HTML elements and attributes
  • JavaScript can react to all existing HTML events in the page
  • JavaScript can create new HTML events on the page

source

How do I get the last character of a string?

public char LastChar(String a){
    return a.charAt(a.length() - 1);
}

Error: "Adb connection Error:An existing connection was forcibly closed by the remote host"

Looks like the installed driver was in bad state. Here is what I did to make it work:

  1. Delete the device from Device Manager.
  2. Rescan for hardware changes.
  3. "Slate 21" will show up with "Unknown driver" status.
  4. Click on "Update Driver" and select /extras/google/usb_driver
  5. Device Manager will find the driver and warn you about installing it. Select "Yes."

This time the device got installed properly.

Note that I didn't have to modify winusb.inf file or update any other driver.

Hope this helps.

How to create correct JSONArray in Java using JSONObject

I suppose you're getting this JSON from a server or a file, and you want to create a JSONArray object out of it.

String strJSON = ""; // your string goes here
JSONArray jArray = (JSONArray) new JSONTokener(strJSON).nextValue();
// once you get the array, you may check items like
JSONOBject jObject = jArray.getJSONObject(0);

Hope this helps :)

How can I count text lines inside an DOM element? Can I?

For those who use jQuery http://jsfiddle.net/EppA2/3/

function getRows(selector) {
    var height = $(selector).height();
    var line_height = $(selector).css('line-height');
    line_height = parseFloat(line_height)
    var rows = height / line_height;
    return Math.round(rows);
}

Could not find an implementation of the query pattern

I had the same error as described by title, but for me it was simply installing Microsoft access 12.0 oledb redistributable to use with LinqToExcel.

Responding with a JSON object in Node.js (converting object/array to JSON string)

var objToJson = { };
objToJson.response = response;
response.write(JSON.stringify(objToJson));

If you alert(JSON.stringify(objToJson)) you will get {"response":"value"}

How to Export Private / Secret ASC Key to Decrypt GPG Files

All the above replies are correct, but might be missing one crucial step, you need to edit the imported key and "ultimately trust" that key

gpg --edit-key (keyIDNumber)
gpg> trust

Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)

  1 = I don't know or won't say
  2 = I do NOT trust
  3 = I trust marginally
  4 = I trust fully
  5 = I trust ultimately
  m = back to the main menu

and select 5 to enable that imported private key as one of your keys

Java: how do I get a class literal from a generic type?

Well as we all know that it gets erased. But it can be known under some circumstances where the type is explicitly mentioned in the class hierarchy:

import java.lang.reflect.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.Collectors;

public abstract class CaptureType<T> {
    /**
     * {@link java.lang.reflect.Type} object of the corresponding generic type. This method is useful to obtain every kind of information (including annotations) of the generic type.
     *
     * @return Type object. null if type could not be obtained (This happens in case of generic type whose information cant be obtained using Reflection). Please refer documentation of {@link com.types.CaptureType}
     */
    public Type getTypeParam() {
        Class<?> bottom = getClass();
        Map<TypeVariable<?>, Type> reifyMap = new LinkedHashMap<>();

        for (; ; ) {
            Type genericSuper = bottom.getGenericSuperclass();
            if (!(genericSuper instanceof Class)) {
                ParameterizedType generic = (ParameterizedType) genericSuper;
                Class<?> actualClaz = (Class<?>) generic.getRawType();
                TypeVariable<? extends Class<?>>[] typeParameters = actualClaz.getTypeParameters();
                Type[] reified = generic.getActualTypeArguments();
                assert (typeParameters.length != 0);
                for (int i = 0; i < typeParameters.length; i++) {
                    reifyMap.put(typeParameters[i], reified[i]);
                }
            }

            if (bottom.getSuperclass().equals(CaptureType.class)) {
                bottom = bottom.getSuperclass();
                break;
            }
            bottom = bottom.getSuperclass();
        }

        TypeVariable<?> var = bottom.getTypeParameters()[0];
        while (true) {
            Type type = reifyMap.get(var);
            if (type instanceof TypeVariable) {
                var = (TypeVariable<?>) type;
            } else {
                return type;
            }
        }
    }

    /**
     * Returns the raw type of the generic type.
     * <p>For example in case of {@code CaptureType<String>}, it would return {@code Class<String>}</p>
     * For more comprehensive examples, go through javadocs of {@link com.types.CaptureType}
     *
     * @return Class object
     * @throws java.lang.RuntimeException If the type information cant be obtained. Refer documentation of {@link com.types.CaptureType}
     * @see com.types.CaptureType
     */
    public Class<T> getRawType() {
        Type typeParam = getTypeParam();
        if (typeParam != null)
            return getClass(typeParam);
        else throw new RuntimeException("Could not obtain type information");
    }


    /**
     * Gets the {@link java.lang.Class} object of the argument type.
     * <p>If the type is an {@link java.lang.reflect.ParameterizedType}, then it returns its {@link java.lang.reflect.ParameterizedType#getRawType()}</p>
     *
     * @param type The type
     * @param <A>  type of class object expected
     * @return The Class<A> object of the type
     * @throws java.lang.RuntimeException If the type is a {@link java.lang.reflect.TypeVariable}. In such cases, it is impossible to obtain the Class object
     */
    public static <A> Class<A> getClass(Type type) {
        if (type instanceof GenericArrayType) {
            Type componentType = ((GenericArrayType) type).getGenericComponentType();
            Class<?> componentClass = getClass(componentType);
            if (componentClass != null) {
                return (Class<A>) Array.newInstance(componentClass, 0).getClass();
            } else throw new UnsupportedOperationException("Unknown class: " + type.getClass());
        } else if (type instanceof Class) {
            Class claz = (Class) type;
            return claz;
        } else if (type instanceof ParameterizedType) {
            return getClass(((ParameterizedType) type).getRawType());
        } else if (type instanceof TypeVariable) {
            throw new RuntimeException("The type signature is erased. The type class cant be known by using reflection");
        } else throw new UnsupportedOperationException("Unknown class: " + type.getClass());
    }

    /**
     * This method is the preferred method of usage in case of complex generic types.
     * <p>It returns {@link com.types.TypeADT} object which contains nested information of the type parameters</p>
     *
     * @return TypeADT object
     * @throws java.lang.RuntimeException If the type information cant be obtained. Refer documentation of {@link com.types.CaptureType}
     */
    public TypeADT getParamADT() {
        return recursiveADT(getTypeParam());
    }

    private TypeADT recursiveADT(Type type) {
        if (type instanceof Class) {
            return new TypeADT((Class<?>) type, null);
        } else if (type instanceof ParameterizedType) {
            ArrayList<TypeADT> generic = new ArrayList<>();
            ParameterizedType type1 = (ParameterizedType) type;
            return new TypeADT((Class<?>) type1.getRawType(),
                    Arrays.stream(type1.getActualTypeArguments()).map(x -> recursiveADT(x)).collect(Collectors.toList()));
        } else throw new UnsupportedOperationException();
    }

}

public class TypeADT {
    private final Class<?> reify;
    private final List<TypeADT> parametrized;

    TypeADT(Class<?> reify, List<TypeADT> parametrized) {
        this.reify = reify;
        this.parametrized = parametrized;
    }

    public Class<?> getRawType() {
        return reify;
    }

    public List<TypeADT> getParameters() {
        return parametrized;
    }
}

And now you can do things like:

static void test1() {
        CaptureType<String> t1 = new CaptureType<String>() {
        };
        equals(t1.getRawType(), String.class);
    }

    static void test2() {
        CaptureType<List<String>> t1 = new CaptureType<List<String>>() {
        };
        equals(t1.getRawType(), List.class);
        equals(t1.getParamADT().getParameters().get(0).getRawType(), String.class);
    }


    private static void test3() {
            CaptureType<List<List<String>>> t1 = new CaptureType<List<List<String>>>() {
            };
            equals(t1.getParamADT().getRawType(), List.class);
        equals(t1.getParamADT().getParameters().get(0).getRawType(), List.class);
    }

    static class Test4 extends CaptureType<List<String>> {
    }

    static void test4() {
        Test4 test4 = new Test4();
        equals(test4.getParamADT().getRawType(), List.class);
    }

    static class PreTest5<S> extends CaptureType<Integer> {
    }

    static class Test5 extends PreTest5<Integer> {
    }

    static void test5() {
        Test5 test5 = new Test5();
        equals(test5.getTypeParam(), Integer.class);
    }

    static class PreTest6<S> extends CaptureType<S> {
    }

    static class Test6 extends PreTest6<Integer> {
    }

    static void test6() {
        Test6 test6 = new Test6();
        equals(test6.getTypeParam(), Integer.class);
    }



    class X<T> extends CaptureType<T> {
    }

    class Y<A, B> extends X<B> {
    }

    class Z<Q> extends Y<Q, Map<Integer, List<List<List<Integer>>>>> {
    }

    void test7(){
        Z<String> z = new Z<>();
        TypeADT param = z.getParamADT();
        equals(param.getRawType(), Map.class);
        List<TypeADT> parameters = param.getParameters();
        equals(parameters.get(0).getRawType(), Integer.class);
        equals(parameters.get(1).getRawType(), List.class);
        equals(parameters.get(1).getParameters().get(0).getRawType(), List.class);
        equals(parameters.get(1).getParameters().get(0).getParameters().get(0).getRawType(), List.class);
        equals(parameters.get(1).getParameters().get(0).getParameters().get(0).getParameters().get(0).getRawType(), Integer.class);
    }




    static void test8() throws IllegalAccessException, InstantiationException {
        CaptureType<int[]> type = new CaptureType<int[]>() {
        };
        equals(type.getRawType(), int[].class);
    }

    static void test9(){
        CaptureType<String[]> type = new CaptureType<String[]>() {
        };
        equals(type.getRawType(), String[].class);
    }

    static class SomeClass<T> extends CaptureType<T>{}
    static void test10(){
        SomeClass<String> claz = new SomeClass<>();
        try{
            claz.getRawType();
            throw new RuntimeException("Shouldnt come here");
        }catch (RuntimeException ex){

        }
    }

    static void equals(Object a, Object b) {
        if (!a.equals(b)) {
            throw new RuntimeException("Test failed. " + a + " != " + b);
        }
    }

More info here. But again, it is almost impossible to retrieve for:

class SomeClass<T> extends CaptureType<T>{}
SomeClass<String> claz = new SomeClass<>();

where it gets erased.

What is the correct way to create a single-instance WPF application?

The following code is my WCF named pipes solution to register a single-instance application. It's nice because it also raises an event when another instance attempts to start, and receives the command line of the other instance.

It's geared toward WPF because it uses the System.Windows.StartupEventHandler class, but this could be easily modified.

This code requires a reference to PresentationFramework, and System.ServiceModel.

Usage:

class Program
{
    static void Main()
    {
        var applicationId = new Guid("b54f7b0d-87f9-4df9-9686-4d8fd76066dc");

        if (SingleInstanceManager.VerifySingleInstance(applicationId))
        {
            SingleInstanceManager.OtherInstanceStarted += OnOtherInstanceStarted;

            // Start the application
        }
    }

    static void OnOtherInstanceStarted(object sender, StartupEventArgs e)
    {
        // Do something in response to another instance starting up.
    }
}

Source Code:

/// <summary>
/// A class to use for single-instance applications.
/// </summary>
public static class SingleInstanceManager
{
  /// <summary>
  /// Raised when another instance attempts to start up.
  /// </summary>
  public static event StartupEventHandler OtherInstanceStarted;

  /// <summary>
  /// Checks to see if this instance is the first instance running on this machine.  If it is not, this method will
  /// send the main instance this instance's startup information.
  /// </summary>
  /// <param name="guid">The application's unique identifier.</param>
  /// <returns>True if this instance is the main instance.</returns>
  public static bool VerifySingleInstace(Guid guid)
  {
    if (!AttemptPublishService(guid))
    {
      NotifyMainInstance(guid);

      return false;
    }

    return true;
  }

  /// <summary>
  /// Attempts to publish the service.
  /// </summary>
  /// <param name="guid">The application's unique identifier.</param>
  /// <returns>True if the service was published successfully.</returns>
  private static bool AttemptPublishService(Guid guid)
  {
    try
    {
      ServiceHost serviceHost = new ServiceHost(typeof(SingleInstance));
      NetNamedPipeBinding binding = new NetNamedPipeBinding(NetNamedPipeSecurityMode.None);
      serviceHost.AddServiceEndpoint(typeof(ISingleInstance), binding, CreateAddress(guid));
      serviceHost.Open();

      return true;
    }
    catch
    {
      return false;
    }
  }

  /// <summary>
  /// Notifies the main instance that this instance is attempting to start up.
  /// </summary>
  /// <param name="guid">The application's unique identifier.</param>
  private static void NotifyMainInstance(Guid guid)
  {
    NetNamedPipeBinding binding = new NetNamedPipeBinding(NetNamedPipeSecurityMode.None);
    EndpointAddress remoteAddress = new EndpointAddress(CreateAddress(guid));
    using (ChannelFactory<ISingleInstance> factory = new ChannelFactory<ISingleInstance>(binding, remoteAddress))
    {
      ISingleInstance singleInstance = factory.CreateChannel();
      singleInstance.NotifyMainInstance(Environment.GetCommandLineArgs());
    }
  }

  /// <summary>
  /// Creates an address to publish/contact the service at based on a globally unique identifier.
  /// </summary>
  /// <param name="guid">The identifier for the application.</param>
  /// <returns>The address to publish/contact the service.</returns>
  private static string CreateAddress(Guid guid)
  {
    return string.Format(CultureInfo.CurrentCulture, "net.pipe://localhost/{0}", guid);
  }

  /// <summary>
  /// The interface that describes the single instance service.
  /// </summary>
  [ServiceContract]
  private interface ISingleInstance
  {
    /// <summary>
    /// Notifies the main instance that another instance of the application attempted to start.
    /// </summary>
    /// <param name="args">The other instance's command-line arguments.</param>
    [OperationContract]
    void NotifyMainInstance(string[] args);
  }

  /// <summary>
  /// The implementation of the single instance service interface.
  /// </summary>
  private class SingleInstance : ISingleInstance
  {
    /// <summary>
    /// Notifies the main instance that another instance of the application attempted to start.
    /// </summary>
    /// <param name="args">The other instance's command-line arguments.</param>
    public void NotifyMainInstance(string[] args)
    {
      if (OtherInstanceStarted != null)
      {
        Type type = typeof(StartupEventArgs);
        ConstructorInfo constructor = type.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, Type.EmptyTypes, null);
        StartupEventArgs e = (StartupEventArgs)constructor.Invoke(null);
        FieldInfo argsField = type.GetField("_args", BindingFlags.Instance | BindingFlags.NonPublic);
        Debug.Assert(argsField != null);
        argsField.SetValue(e, args);

        OtherInstanceStarted(null, e);
      }
    }
  }
}

Use CSS3 transitions with gradient backgrounds

As stated. Gradients aren't currently supported with CSS Transitions. But you could work around it in some cases by setting one of the colors to transparent, so that the background-color of some other wrapping element shines through, and transition that instead.

CSS selector - element with a given child

Update 2019

The :has() pseudo-selector is propsed in the CSS Selectors 4 spec, and will address this use case once implemented.

To use it, we will write something like:

.foo > .bar:has(> .baz) { /* style here */ }

In a structure like:

<div class="foo">
  <div class="bar">
    <div class="baz">Baz!</div>
  </div>
</div>

This CSS will target the .bar div - because it both has a parent .foo and from its position in the DOM, > .baz resolves to a valid element target.


Original Answer (left for historical purposes) - this portion is no longer accurate

For completeness, I wanted to point out that in the Selectors 4 specification (currently in proposal), this will become possible. Specifically, we will gain Subject Selectors, which will be used in the following format:

!div > span { /* style here */

The ! before the div selector indicates that it is the element to be styled, rather than the span. Unfortunately, no modern browsers (as of the time of this posting) have implemented this as part of their CSS support. There is, however, support via a JavaScript library called Sel, if you want to go down the path of exploration further.

BSTR to std::string (std::wstring) and vice versa

There is a c++ class called _bstr_t. It has useful methods and a collection of overloaded operators.

For example, you can easily assign from a const wchar_t * or a const char * just doing _bstr_t bstr = L"My string"; Then you can convert it back doing const wchar_t * s = bstr.operator const wchar_t *();. You can even convert it back to a regular char const char * c = bstr.operator char *(); You can then just use the const wchar_t * or the const char * to initialize a new std::wstring oe std::string.

subsampling every nth entry in a numpy array

You can use numpy's slicing, simply start:stop:step.

>>> xs
array([1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4])
>>> xs[1::4]
array([2, 2, 2])

This creates a view of the the original data, so it's constant time. It'll also reflect changes to the original array and keep the whole original array in memory:

>>> a
array([1, 2, 3, 4, 5])
>>> b = a[::2]         # O(1), constant time
>>> b[:] = 0           # modifying the view changes original array
>>> a                  # original array is modified
array([0, 2, 0, 4, 0])

so if either of the above things are a problem, you can make a copy explicitly:

>>> a
array([1, 2, 3, 4, 5])
>>> b = a[::2].copy()  # explicit copy, O(n)
>>> b[:] = 0           # modifying the copy
>>> a                  # original is intact
array([1, 2, 3, 4, 5])

This isn't constant time, but the result isn't tied to the original array. The copy also contiguous in memory, which can make some operations on it faster.

Do you know the Maven profile for mvnrepository.com?

Place this in the ~/.m2/settings.xml or custom file to be run with $ mvn -s custom-settings.xml install

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
https://maven.apache.org/xsd/settings-1.0.0.xsd">
<localRepository>${user.home}/.m2/repository</localRepository>
<interactiveMode/>
<offline/>
<pluginGroups/>
<profiles>
    <profile>
        <repositories>
            <repository>
                <id>mvnrepository</id>
                <name>mvnrepository</name>
                <url>http://www.mvnrepository.com</url>
            </repository>
        </repositories>
    </profile>
</profiles>
<activeProfiles>
    <activeProfile>mvnrepository</activeProfile>
</activeProfiles>
</settings>

jQuery check if <input> exists and has a value

You can create your own custom selector :hasValue and then use that to find, filter, or test any other jQuery elements.

jQuery.expr[':'].hasValue = function(el,index,match) {
  return el.value != "";
};

Then you can find elements like this:

var data = $("form input:hasValue").serialize();

Or test the current element with .is()

var elHasValue = $("#name").is(":hasValue");

_x000D_
_x000D_
jQuery.expr[':'].hasValue = function(el) {_x000D_
  return el.value != "";_x000D_
};_x000D_
_x000D_
_x000D_
var data = $("form input:hasValue").serialize();_x000D_
console.log(data)_x000D_
_x000D_
_x000D_
var elHasValue = $("[name='LastName']").is(":hasValue");_x000D_
console.log(elHasValue)
_x000D_
label { display: block; margin-top:10px; }
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
_x000D_
<form>_x000D_
  <label>_x000D_
    First Name:_x000D_
    <input type="text" name="FirstName" value="Frida" />_x000D_
  </label>_x000D_
_x000D_
  <label>_x000D_
    Last Name:_x000D_
    <input type="text" name="LastName" />_x000D_
  </label>_x000D_
</form>
_x000D_
_x000D_
_x000D_

Further Reading:

How to make a phone call using intent in Android?

11-25 14:47:01.681: ERROR/AndroidRuntime(302): blah blah...requires android.permission.CALL_PHONE

^ The answer lies in the exception output "requires android.permission.CALL_PHONE" :)

How to switch between hide and view password

private boolean isPasswordVisible;

private TextInputEditText firstEditText;

...

firstEditText = findViewById(R.id.et_first);

...

    private void togglePassVisability() {
    if (isPasswordVisible) {
        String pass = firstEditText.getText().toString();
        firstEditText.setTransformationMethod(PasswordTransformationMethod.getInstance());
        firstEditText.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
        firstEditText.setText(pass);
        firstEditText.setSelection(pass.length());           
    } else {
        String pass = firstEditText.getText().toString();
        firstEditText.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
        firstEditText.setInputType(InputType.TYPE_CLASS_TEXT);
        firstEditText.setText(pass);
        firstEditText.setSelection(pass.length());
    }
    isPasswordVisible= !isPasswordVisible;
}

sqlplus: error while loading shared libraries: libsqlplus.so: cannot open shared object file: No such file or directory

I did solve this error by setting

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME/lib:$ORACLE_HOME

yes, not only $ORACLE_HOME/lib but $ORACLE_HOME too.

XPath to get all child nodes (elements, comments, and text) without parent

From the documentation of XPath ( http://www.w3.org/TR/xpath/#location-paths ):

child::* selects all element children of the context node

child::text() selects all text node children of the context node

child::node() selects all the children of the context node, whatever their node type

So I guess your answer is:

$doc/PRESENTEDIN/X/child::node()

And if you want a flatten array of all nested nodes:

$doc/PRESENTEDIN/X/descendant::node()

Auto expand a textarea using jQuery

@Georgiy Ivankin made a suggestion in a comment, I used it successfully :) -- , but with slight changes:

$('#note').on('keyup',function(e){
    var maxHeight = 200; 
    var f = document.getElementById('note'); 
    if (f.clientHeight < f.scrollHeight && f.scrollHeight < maxHeight ) 
        { f.style.height = f.scrollHeight + 'px'; }
    });      

It stops expanding after it reaches max height of 200px

why windows 7 task scheduler task fails with error 2147942667

For a more generic answer, convert the error value to hex, then lookup the hex value at Windows Task Scheduler Error and Success Constants

How would I get a cron job to run every 30 minutes?

Try this:

0,30 * * * * your command goes here

According to the official Mac OS X crontab(5) manpage, the / syntax is supported. Thus, to figure out why it wasn't working for you, you'll need to look at the logs for cron. In those logs, you should find a clear failure message.

Note: Mac OS X appears to use Vixie Cron, the same as Linux and the BSDs.

Difference between session affinity and sticky session?

They are Synonyms. No Difference At all

Sticky Session / Session Affinity:

Affinity/Stickiness/Contact between user session and, the server to which user request is sent is retained.

SQL query to find Nth highest salary from a salary table

To get 2nd highest salary:

SELECT   salary 
FROM     [employees] 
ORDER BY salary DESC 
offset   1 rows 
FETCH next 1 rows only

To get Nth highest salary:

SELECT   salary 
FROM     [employees] 
ORDER BY salary DESC 
offset   **n-1** rows 
FETCH next 1 rows only

How to get a cookie from an AJAX response?

Similar to yebmouxing I could not the

 xhr.getResponseHeader('Set-Cookie');

method to work. It would only return null even if I had set HTTPOnly to false on my server.

I too wrote a simple js helper function to grab the cookies from the document. This function is very basic and only works if you know the additional info (lifespan, domain, path, etc. etc.) to add yourself:

function getCookie(cookieName){
  var cookieArray = document.cookie.split(';');
  for(var i=0; i<cookieArray.length; i++){
    var cookie = cookieArray[i];
    while (cookie.charAt(0)==' '){
      cookie = cookie.substring(1);
    }
    cookieHalves = cookie.split('=');
    if(cookieHalves[0]== cookieName){
      return cookieHalves[1];
    }
  }
  return "";
}

How does internationalization work in JavaScript?

Localization support in legacy browsers is poor. Originally, this was due to phrases in the ECMAScript language spec that look like this:

Number.prototype.toLocaleString()
Produces a string value that represents the value of the Number formatted according to the conventions of the host environment’s current locale. This function is implementation-dependent, and it is permissible, but not encouraged, for it to return the same thing as toString.

Every localization method defined in the spec is defined as "implementation-dependent", which results in a lot of inconsistencies. In this instance, Chrome Opera and Safari would return the same thing as .toString(). Firefox and IE will return locale formatted strings, and IE even includes a thousand separator (perfect for currency strings). Chrome was recently updated to return a thousands-separated string, though with no fixed decimal.

For modern environments, the ECMAScript Internationalization API spec, a new standard that complements the ECMAScript Language spec, provides much better support for string comparison, number formatting, and the date and time formatting; it also fixes the corresponding functions in the Language Spec. An introduction can be found here. Implementations are available in:

  • Chrome 24
  • Firefox 29
  • Internet Explorer 11
  • Opera 15

There is also a compatibility implementation, Intl.js, which will provide the API in environments where it doesn't already exist.

Determining the user's preferred language remains a problem since there's no specification for obtaining the current language. Each browser implements a method to obtain a language string, but this could be based on the user's operating system language or just the language of the browser:

// navigator.userLanguage for IE, navigator.language for others
var lang = navigator.language || navigator.userLanguage;

A good workaround for this is to dump the Accept-Language header from the server to the client. If formatted as a JavaScript, it can be passed to the Internationalization API constructors, which will automatically pick the best (or first-supported) locale.

In short, you have to put in a lot of the work yourself, or use a framework/library, because you cannot rely on the browser to do it for you.

Various libraries and plugins for localization:

  • Others:

Feel free to add/edit.

Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array

UPDATED: The following uses an optimized combined strategy. It optimizes primitive lookups to benefit from hash O(1) lookup time (running unique on an array of primitives is O(n)). Object lookups are optimized by tagging objects with a unique id while iterating through so so identifying duplicate objects is also O(1) per item and O(n) for the whole list. The only exception is items that are frozen, but those are rare and a fallback is provided using an array and indexOf.

var unique = function(){
  var hasOwn = {}.hasOwnProperty,
      toString = {}.toString,
      uids = {};

  function uid(){
    var key = Math.random().toString(36).slice(2);
    return key in uids ? uid() : uids[key] = key;
  }

  function unique(array){
    var strings = {}, numbers = {}, others = {},
        tagged = [], failed = [],
        count = 0, i = array.length,
        item, type;

    var id = uid();

    while (i--) {
      item = array[i];
      type = typeof item;
      if (item == null || type !== 'object' && type !== 'function') {
        // primitive
        switch (type) {
          case 'string': strings[item] = true; break;
          case 'number': numbers[item] = true; break;
          default: others[item] = item; break;
        }
      } else {
        // object
        if (!hasOwn.call(item, id)) {
          try {
            item[id] = true;
            tagged[count++] = item;
          } catch (e){
            if (failed.indexOf(item) === -1)
              failed[failed.length] = item;
          }
        }
      }
    }

    // remove the tags
    while (count--)
      delete tagged[count][id];

    tagged = tagged.concat(failed);
    count = tagged.length;

    // append primitives to results
    for (i in strings)
      if (hasOwn.call(strings, i))
        tagged[count++] = i;

    for (i in numbers)
      if (hasOwn.call(numbers, i))
        tagged[count++] = +i;

    for (i in others)
      if (hasOwn.call(others, i))
        tagged[count++] = others[i];

    return tagged;
  }

  return unique;
}();

If you have ES6 Collections available, then there is a much simpler and significantly faster version. (shim for IE9+ and other browsers here: https://github.com/Benvie/ES6-Harmony-Collections-Shim)

function unique(array){
  var seen = new Set;
  return array.filter(function(item){
    if (!seen.has(item)) {
      seen.add(item);
      return true;
    }
  });
}

How to open port in Linux

First, you should disable selinux, edit file /etc/sysconfig/selinux so it looks like this:

SELINUX=disabled
SELINUXTYPE=targeted

Save file and restart system.

Then you can add the new rule to iptables:

iptables -A INPUT -m state --state NEW -p tcp --dport 8080 -j ACCEPT

and restart iptables with /etc/init.d/iptables restart

If it doesn't work you should check other network settings.

If else on WHERE clause

Here is a sample query for a table having a foreign key relationship to the same table with a query parameter.

enter image description here

SET @x = -1;
SELECT id, categoryName 
FROM Catergory WHERE IF(@x > 0,category_ParentId = @x,category_ParentId IS NOT NULL);

@x can be changed.

Why I am Getting Error 'Channel is unrecoverably broken and will be disposed!'

As I faced this error, somewhere in your code your funcs or libraries that used run on different threads, so try to call all code on the same thread , it fixed my problem.

If you call methods on WebView from any thread other than your app's UI thread, it can cause unexpected results. For example, if your app uses multiple threads, you can use the runOnUiThread() method to ensure your code executes on the UI thread:

Google reference link

How to filter object array based on attributes?

const state.contactList = [{
    name: 'jane',
    email: '[email protected]'
  },{},{},...]

const fileredArray = state.contactsList.filter((contactItem) => {
  const regex = new RegExp(`${action.payload}`, 'gi');
  return contactItem.nameProperty.match(regex) || 
    contactItem.emailProperty.match(regex);
});


// contactList: all the contacts stored in state
// action.payload: whatever typed in search field

Set the value of an input field

Try out these.

document.getElementById("current").value = 12

// or

var current = document.getElementById("current");
current.value = 12

Negate if condition in bash script

You can choose:

if [[ $? -ne 0 ]]; then       # -ne: not equal

if ! [[ $? -eq 0 ]]; then     # -eq: equal

if [[ ! $? -eq 0 ]]; then

! inverts the return of the following expression, respectively.

When should an IllegalArgumentException be thrown?

As specified in oracle official tutorial , it states that:

If a client can reasonably be expected to recover from an exception, make it a checked exception. If a client cannot do anything to recover from the exception, make it an unchecked exception.

If I have an Application interacting with database using JDBC , And I have a method that takes the argument as the int item and double price. The price for corresponding item is read from database table. I simply multiply the total number of item purchased with the price value and return the result. Although I am always sure at my end(Application end) that price field value in the table could never be negative .But what if the price value comes out negative? It shows that there is a serious issue with the database side. Perhaps wrong price entry by the operator. This is the kind of issue that the other part of application calling that method can't anticipate and can't recover from it. It is a BUG in your database. So , and IllegalArguementException() should be thrown in this case which would state that the price can't be negative.
I hope that I have expressed my point clearly..

How to concatenate two strings in C++?

It is better to use C++ string class instead of old style C string, life would be much easier.

if you have existing old style string, you can covert to string class

    char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
    cout<<greeting + "and there \n"; //will not compile because concat does \n not work on old C style string
    string trueString = string (greeting);
    cout << trueString + "and there \n"; // compiles fine
    cout << trueString + 'c'; // this will be fine too. if one of the operand if C++ string, this will work too

Double free or corruption after queue::push

Let's talk about copying objects in C++.

Test t;, calls the default constructor, which allocates a new array of integers. This is fine, and your expected behavior.

Trouble comes when you push t into your queue using q.push(t). If you're familiar with Java, C#, or almost any other object-oriented language, you might expect the object you created earler to be added to the queue, but C++ doesn't work that way.

When we take a look at std::queue::push method, we see that the element that gets added to the queue is "initialized to a copy of x." It's actually a brand new object that uses the copy constructor to duplicate every member of your original Test object to make a new Test.

Your C++ compiler generates a copy constructor for you by default! That's pretty handy, but causes problems with pointer members. In your example, remember that int *myArray is just a memory address; when the value of myArray is copied from the old object to the new one, you'll now have two objects pointing to the same array in memory. This isn't intrinsically bad, but the destructor will then try to delete the same array twice, hence the "double free or corruption" runtime error.

How do I fix it?

The first step is to implement a copy constructor, which can safely copy the data from one object to another. For simplicity, it could look something like this:

Test(const Test& other){
    myArray = new int[10];
    memcpy( myArray, other.myArray, 10 );
}

Now when you're copying Test objects, a new array will be allocated for the new object, and the values of the array will be copied as well.

We're not completely out trouble yet, though. There's another method that the compiler generates for you that could lead to similar problems - assignment. The difference is that with assignment, we already have an existing object whose memory needs to be managed appropriately. Here's a basic assignment operator implementation:

Test& operator= (const Test& other){
    if (this != &other) {
        memcpy( myArray, other.myArray, 10 );
    }
    return *this;
}

The important part here is that we're copying the data from the other array into this object's array, keeping each object's memory separate. We also have a check for self-assignment; otherwise, we'd be copying from ourselves to ourselves, which may throw an error (not sure what it's supposed to do). If we were deleting and allocating more memory, the self-assignment check prevents us from deleting memory from which we need to copy.

Is a LINQ statement faster than a 'foreach' loop?

LINQ is slower now, but it might get faster at some point. The good thing about LINQ is that you don't have to care about how it works. If a new method is thought up that's incredibly fast, the people at Microsoft can implement it without even telling you and your code would be a lot faster.

More importantly though, LINQ is just much easier to read. That should be enough reason.

Google Chrome default opening position and size

Maybe a little late, but I found an easier way to set the defaults! You have to right-click on the right of your tab and choose "size", then click on your window, and it should keep it as the default size.

When to create variables (memory management)

I've heard that you must set a variable to 'null' once you're done using it so the garbage collector can get to it (if it's a field var).

This is very rarely a good idea. You only need to do this if the variable is a reference to an object which is going to live much longer than the object it refers to.

Say you have an instance of Class A and it has a reference to an instance of Class B. Class B is very large and you don't need it for very long (a pretty rare situation) You might null out the reference to class B to allow it to be collected.

A better way to handle objects which don't live very long is to hold them in local variables. These are naturally cleaned up when they drop out of scope.

If I were to have a variable that I won't be referring to agaon, would removing the reference vars I'm using (and just using the numbers when needed) save memory?

You don't free the memory for a primitive until the object which contains it is cleaned up by the GC.

Would that take more space than just plugging '5' into the println method?

The JIT is smart enough to turn fields which don't change into constants.

Been looking into memory management, so please let me know, along with any other advice you have to offer about managing memory

Use a memory profiler instead of chasing down 4 bytes of memory. Something like 4 million bytes might be worth chasing if you have a smart phone. If you have a PC, I wouldn't both with 4 million bytes.

Sleep for milliseconds

nanosleep is a better choice than usleep - it is more resilient against interrupts.

How to tell if tensorflow is using gpu acceleration from inside python shell?

>>> import tensorflow as tf 
>>> tf.config.list_physical_devices('GPU')

2020-05-10 14:58:16.243814: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcuda.so.1
2020-05-10 14:58:16.262675: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:981] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
2020-05-10 14:58:16.263119: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1555] Found device 0 with properties:
pciBusID: 0000:01:00.0 name: GeForce GTX 1060 6GB computeCapability: 6.1
coreClock: 1.7715GHz coreCount: 10 deviceMemorySize: 5.93GiB deviceMemoryBandwidth: 178.99GiB/s
2020-05-10 14:58:16.263143: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcudart.so.10.1
2020-05-10 14:58:16.263188: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcublas.so.10
2020-05-10 14:58:16.264289: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcufft.so.10
2020-05-10 14:58:16.264495: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcurand.so.10
2020-05-10 14:58:16.265644: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcusolver.so.10
2020-05-10 14:58:16.266329: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcusparse.so.10
2020-05-10 14:58:16.266357: I tensorflow/stream_executor/platform/default/dso_loader.cc:44] Successfully opened dynamic library libcudnn.so.7
2020-05-10 14:58:16.266478: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:981] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
2020-05-10 14:58:16.266823: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:981] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
2020-05-10 14:58:16.267107: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1697] Adding visible gpu devices: 0
[PhysicalDevice(name='/physical_device:GPU:0', device_type='GPU')]

As suggested by @AmitaiIrron:

This section indicates that a gpu was found

2020-05-10 14:58:16.263119: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1555] Found device 0 with properties:

pciBusID: 0000:01:00.0 name: GeForce GTX 1060 6GB computeCapability: 6.1
coreClock: 1.7715GHz coreCount: 10 deviceMemorySize: 5.93GiB deviceMemoryBandwidth: 178.99GiB/s

And here that it got added as an available physical device

2020-05-10 14:58:16.267107: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1697] Adding visible gpu devices: 0

[PhysicalDevice(name='/physical_device:GPU:0', device_type='GPU')]