Tutorial by Examples: for

You can detect when a user Clicked on a HelpButton on title-bar of form by handling HelpButtonClicked. You can let the event continue or cancel it by setting Cancel property of its event args to true. private void Form1_HelpButtonClicked(object sender, CancelEventArgs e) { e.Cancel = true; ...

Default behavior when cloning an object is to perform a shallow copy of the object's fields. In that case, both the original object and the cloned object, hold references to the same objects. This example shows that behavior. import java.util.List; public class Sheep implements Cloneable { ...

To copy nested objects, a deep copy must be performed, as shown in this example. import java.util.ArrayList; import java.util.List; public class Sheep implements Cloneable { private String name; private int weight; private List<Sheep> children; public Sheep(Str...

The Kotlin Standard Library also provides numerous useful functions to iteratively work upon collections. For example, the map function can be used to transform a list of items. val numbers = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 0) val numberStrings = numbers.map { "Number $it" } One of...

Coming from imperative languages many developers wonder how to write a for-loop that exits early as F# doesn't support break, continue or return. The answer in F# is to use tail-recursion which is a flexible and idiomatic way to iterate while still providing excellent performance. Say we want to ...

Often in R you'll want to know things about an object or variable you're working with. This can be useful when reading someone else's code or even your own, especially when using packages that are new to you. Suppose we create a variable a: a <- matrix(1:9, 3, 3) What data type is this? Yo...

One common scenario is to wait for a number of requests to finish before continuing. This can be accomplished using the forkJoin method. In the following example, forkJoin is used to call two methods that return Observables. The callback specified in the .subscribe method will be called when both O...

Some properties are not automatically inherited from an element down to its' children. This is because those properties are typically desired to be unique to the element (or selection of elements) to which the property is applied to. Common such properties are margin, padding, background, display, e...

To ensure that our collection can be iterated using iterator or for-each loop, we have to take care of following steps: The stuff we want to iterate upon has to be Iterable and expose iterator(). Design a java.util.Iterator by overriding hasNext(), next() and remove(). I have added a simple ...

A For Loop is great for doing things a certain amount of time. It's like a While Loop but the increment is included with the condition. A For Loop is set up like this: for (Initialization; Condition; Increment) { // Code } Initialization - Makes a new local variable that can only be us...

In some cases you might want to add an additional description to an enum value, for instance when the enum value itself is less readable than what you might want to display to the user. In such cases you can use the System.ComponentModel.DescriptionAttribute class. For example: public enum Possibl...

Detecting the current state of the network connection and responding to any changes that might occur, can be done by using one of several plugins. This example is about the cordova-plugin-network-information plugin. Add the plugin to the project: cordova plugin add cordova-plugin-network-informati...

Counting rows based on a specific column value: SELECT category, COUNT(*) AS item_count FROM item GROUP BY category; Getting average income by department: SELECT department, AVG(income) FROM employees GROUP BY department; The important thing is to select only columns specified in the GRO...

One way to calculate the Big-O value of a procedure you've written is to determine which line of code runs the most times in your function, given your input size n. Once you have that number, take out all but the fastest-growing terms and get rid of the coefficents - that is the Big-O notation of yo...

gitk path/to/myfile

Write formatted data to string int sprintf ( char * str, const char * format, ... ); use sprintf function to write float data to string. #include <stdio.h> int main () { char buffer [50]; double PI = 3.1415926; sprintf (buffer, "PI = %.7f", PI); printf ("%s\n&...

If you need to add custom headers to your volley requests, you can't do this after initialisation, as the headers are saved in a private variable. Instead, you need to override the getHeaders() method of Request.class as such: new JsonObjectRequest(REQUEST_METHOD, REQUEST_URL, REQUEST_BODY, RESP_L...

Configure your app's URLconf to automatically use a URL namespace by setting the app_name attribute: # In <myapp>/urls.py from django.conf.urls import url from .views import overview app_name = 'myapp' urlpatterns = [ url(r'^$', overview, name='overview'), ] This will set t...

The query attribute on queryset gives you SQL equivalent syntax for your query. >>> queryset = MyModel.objects.all() >>> print(queryset.query) SELECT "myapp_mymodel"."id", ... FROM "myapp_mymodel" Warning: This output should only be used for d...

XE2 program CrossPlatformHelloWorld; uses FMX.Dialogs; {$R *.res} begin ShowMessage('Hello world!'); end. Most of the Delphi supported platforms (Win32/Win64/OSX32/Android32/iOS32/iOS64) also support a console so the WriteLn example fits them well. For the platforms that require...