Tutorial by Examples: u

Using a handler function

HandleFunc registers the handler function for the given pattern in the server mux (router). You can pass define an anonymous function, as we have seen in the basic Hello World example: http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, "Hello, w...

Go • HTTP Server

Creating an error value

The simplest way to create an error is by using the errors package. errors.New("this is an error") If you want to add additional information to an error, the fmt package also provides a useful error creation method: var f float64 fmt.Errorf("error with some additional informatio...

Go • Error Handling

Creating a custom error type

In Go, an error is represented by any value that can describe itself as string. Any type that implement the built-in error interface is an error. // The error interface is represented by a single // Error() method, that returns a string representation of the error type error interface { Erro...

Go • Error Handling

Returning an error

In Go you don't raise an error. Instead, you return an error in case of failure. // This method can fail func DoSomething() error { // functionThatReportsOK is a side-effecting function that reports its // state as a boolean. NOTE: this is not a good practice, so this example // tur...

Go • Error Handling

Absolute minimum example

Any Chrome extension starts as an unpacked extension: a folder containing the extension's files. One file it must contain is manifest.json, which describes the basic properties of the extension. Many of the properties in that file are optional, but here is an absolute minimum manifest.json file: ...

google-chrome-extension • Getting started with google-chrome-extension

Retrieve all stored entries from a particular SharedPreferences file

The getAll() method retrieves all values from the preferences. We can use it, for instance, to log the current content of the SharedPreferences: private static final String PREFS_FILE = "MyPrefs"; public static void logSharedPreferences(final Context context) { SharedPreferences s...

Android • SharedPreferences

Interface and class documentation comments

/// <summary> /// This interface can do Foo /// </summary> public interface ICanDoFoo { // ... } /// <summary> /// This Bar class implements ICanDoFoo interface /// </summary> public class Bar : ICanDoFoo { // ... } Result Interface summary Clas...

C# Language • XML Documentation Comments

Installation or Setup

Yii2 can be installed in two ways. They are Installing via Composer Installing from an Archive File Installing via Composer Installing Composer If you do not already have Composer installed, you may do so by following the instructions at getcomposer.org. On Linux and Mac OS X, you'll run th...

yii2 • Getting started with yii2

Creating a UITableView

A Table View is a list of rows that can be selected. Each row is populated from a data source. This example creates a simple table view in which each row is a single line of text. Add a UITableView to your Storyboard Although there are a number of ways to create a UITableView, one of the easiest...

iOS • UITableView

How to use Auto Layout

Auto layout is used to arrange views so that they look good on any device and orientation. Constraints are the rules that tell how everything should be laid down. They include pinning edges, centering, and setting sizes, among other things. Auto layout is enabled by default, but you can double chec...

iOS • Auto Layout

Installation or Setup

Detailed instructions on getting pandas set up or installed can be found here in the official documentation. Installing pandas with Anaconda Installing pandas and the rest of the NumPy and SciPy stack can be a little difficult for inexperienced users. The simplest way to install not only pandas, ...

pandas • Getting started with pandas

Number

5 <input type="number" value="0" name="quantity"> The Input element with a type attribute whose value is number represents a precise control for setting the element’s value to a string representing a number. Please note that this field does not guarantee to h...

HTML • Input Control Elements

Installation or Setup

ReactJS is a JavaScript library contained in a single file react-<version>.js that can be included in any HTML page. People also commonly install the React DOM library react-dom-<version>.js along with the main React file: Basic Inclusion <!DOCTYPE html> <html> <...

React • Getting started with React

Create an XML file using XMLWriter

Instantiate a XMLWriter object: $xml = new XMLWriter(); Next open the file to which you want to write. For example, to write to /var/www/example.com/xml/output.xml, use: $xml->openUri('file:///var/www/example.com/xml/output.xml'); To start the document (create the XML open tag): $xml-&gt...

PHP • XML

Show both staged and unstaged changes

To show all staged and unstaged changes, use: git diff HEAD NOTE: You can also use the following command: git status -vv The difference being that the output of the latter will actually tell you which changes are staged for commit and which are not.

Git • Git Diff

Installation or Setup

Knockout is available on most JavaScript platforms, or as a standalone script. Include as a script You can download the script from it's download page, then include it in your page with a standard script tag <script type='text/javascript' src='knockout-3.4.0.js'></script> Using a C...

knockout.js • Getting started with knockout.js

Use anonymous functions with apply

apply is used to evaluate a function (maybe an anonymous one) over the margins of an array or matrix. Let's use the iris dataset to illustrate this idea. The iris dataset has measurements of 150 flowers from 3 species. Let's see how this dataset is structured: > head(iris) Sepal.Length Sep...

R Language • *apply family of functions (functionals)

Enum Polymorphism Pattern

When a method need to accept an "extensible" set of enum values, the programmer can apply polymorphism like on a normal class by creating an interface which will be used anywere where the enums shall be used: public interface ExtensibleEnum { String name(); } This way, any enum t...

Java Language • Enums

Install Yii2 advanced in ubuntu

First we need to install composer. Steps to install composer Install Composer. curl -sS https://getcomposer.org/installer | php Now change directory: sudo mv composer.phar /usr/local/bin/composer Check composer working composer Now Composer installed. There two ways to install Yii2 adv...

yii2 • Getting started with yii2

Manipulating Array Elements

Adding elements: [1, 2, 3] << 4 # => [1, 2, 3, 4] [1, 2, 3].push(4) # => [1, 2, 3, 4] [1, 2, 3].unshift(4) # => [4, 1, 2, 3] [1, 2, 3] << [4, 5] # => [1, 2, 3, [4, 5]] Removing elements: array = [1, 2, 3, 4] array.pop # => 4 array # => [1, 2, 3] ...

Ruby Language • Arrays