Tutorial by Examples: e

Boolean operators

There are two kinds of boolean operators in Elixir: boolean operators (they expect either true or false as their first argument) x or y # true if x is true, otherwise y x and y # false if x is false, otherwise y not x # false if x is true, otherwise true All of booleans...

Comparison operators

Equality: value equality x == y (1 == 1.0 # true) value inequality x == y (1 != 1.0 # false) strict equality x === y (1 === 1.0 # false) strict inequality x === y (1 !== 1.0 # true) Comparison: x > y x >= y x < y x <= y If types are compatible, comparison uses natural o...

Implicit and Explicit Intents

An explicit intent is used for starting an activity or service within the same application package. In this case the name of the intended class is explicitly mentioned: Intent intent = new Intent(this, MyComponent.class); startActivity(intent); However, an implicit intent is sent across the sys...

Header Include Guards

Pretty much every header file should follow the include guard idiom: my-header-file.h #ifndef MY_HEADER_FILE_H #define MY_HEADER_FILE_H // Code body for header file #endif This ensures that when you #include "my-header-file.h" in multiple places, you don't get duplicate declara...

AJAX request with a JSON response

functions.php: // We add the action twice, once for logged in users and once for non logged in users. add_action( 'wp_ajax_my_action', 'my_action_callback' ); add_action( 'wp_ajax_nopriv_my_action', 'my_action_callback' ); // Enqueue the script on the front end. add_action( 'wp_enqueue_script...

Attach and Detach Event Handlers

Attach an Event Handler Since version 1.7 jQuery has the event API .on(). This way any standard javascript event or custom event can be bound on the currently selected jQuery element. There are shortcuts such as .click(), but .on() gives you more options. HTML <button id="foo">b...

Delegated Events

Let's start with example. Here is a very simple example HTML. Example HTML <html> <head> </head> <body> <ul> <li> <a href="some_url/">Link 1</a> </li> &l...

Document Loading Event .load()

If you want your script to wait until a certain resource was loaded, such as an image or a PDF you can use .load(), which is a shortcut for shortcut for .on( "load", handler). HTML <img src="image.jpeg" alt="image" id="image"> jQuery $( "#imag...

Creating a UIColor from hexadecimal number or string

You can create a UIColor from a hexadecimal number or string, e.g. 0xff00cc, "#FFFFFF" Swift Int Value extension UIColor { convenience init(hex: Int, alpha: CGFloat = 1.0) { let r = CGFloat((hex >> 16) & 0xff) / 255 let g = CGFloat((hex >> 08) &amp...
iOS • UIColor

Iterating over list of jQuery elements

When you need to iterate over the list of jQuery elements. Consider this DOM structure: <div class="container"> <div class="red one">RED 1 Info</div> <div class="red two">RED 2 Info</div> <div class="red three"...

Selecting siblings

To select siblings of an item you can use the .siblings() method. A typical example where you want to modify the siblings of an item is in a menu: <ul class="menu"> <li class="selected">Home</li> <li>Blog</li> <li>About</li&...

Using Imports In ES6

Node.js is built against modern versions of V8. By keeping up-to-date with the latest releases of this engine, we ensure new features from the JavaScript ECMA-262 specification are brought to Node.js developers in a timely manner, as well as continued performance and stability improvements. All ECM...

closest() method

Returns the first element that matches the selector starting at the element and traversing up the DOM tree. HTML <div id="abc" class="row"> <div id="xyz" class="row"> </div> <p id="origin"> Hello &...

Accessing character substrings

For the character entity character(len=5), parameter :: greeting = "Hello" a substring may be referenced with the syntax greeting(2:4) ! "ell" To access a single letter it isn't sufficient to write greeting(1) ! This isn't the letter "H" but greeting(1:...

Accessing complex components

The complex entity complex, parameter :: x = (1., 4.) has real part 1. and complex part 4.. We can access these individual components as real(x) ! The real component aimag(x) ! The complex component x%re ! The real component y%im ! The complex component The x%.. form is new to F...

GET requests

requests.get() creates a GET request: response = requests.get('https://example.com/') Pass in query parameters as a dictionary to the params argument: response = requests.get('https://example.com/', params={"a": 1, "b": 2}) For GET requests that might require basic authen...

Adding comments

There are three types of comment: # This comment continues to the end of line -- This comment continues to the end of line /* This is an in-line comment */ /* This is a multiple-line comment */ Example: SELECT * FROM t1; -- this is comment CREATE TABLE stack( /*id_user int...

Custom Filters

Filters allows you to apply a function to a variable. This function may take 0 or 1 argument. Here is the syntax: {{ variable|filter_name }} {{ variable|filter_name:argument }} Filters can be chained so this is perfectly valid: {{ variable|filter_name:argument|another_filter }} If transla...

Simple tags

The simplest way of defining a custom template tag is to use a simple_tag. These are very straightforward to setup. The function name will be the tag name (though you can override it), and arguments will be tokens ("words" separated by spaces, except spaces enclosed between quotes). It eve...

Advanced custom tags using Node

Sometimes what you want to do is just too complex for a filter or a simple_tag. Fow this you will need to create a compilation function and a renderer. In this example we will create a template tag verbose_name with the following syntax: ExampleDescription{% verbose_name obj %}Verbose name of a mo...

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