Tutorial by Examples: e

Leaked variables in list comprehension

Python 2.x2.3 x = 'hello world!' vowels = [x for x in 'AEIOU'] print (vowels) # Out: ['A', 'E', 'I', 'O', 'U'] print(x) # Out: 'U' Python 3.x3.0 x = 'hello world!' vowels = [x for x in 'AEIOU'] print (vowels) # Out: ['A', 'E', 'I', 'O', 'U'] print(x) # Out: 'hello world!' ...

Python Language • Incompatibilities moving from Python 2 to Python 3

Add column with default value

The following example adds a column admin to the users table, and gives that column the default value false. class AddDetailsToUsers < ActiveRecord::Migration[5.0] def change add_column :users, :admin, :boolean, default: false end end Migrations with defaults might take a long tim...

Ruby on Rails • ActiveRecord Migrations

Set

To set the options - use :set instruction. Example: :set ts=4 :set shiftwidth=4 :set expandtab :set autoindent To view the current value of the option - type :set {option}?. Example: :set ts? To reset the value of the option to its default - type :set {option}&. Example: :set ts&...

vim • Vim Options

Indentation

Width To make indentations 4 spaces wide: :set shiftwidth=4 Spaces To use spaces as indents, 4 spaces wide: :set expandtab :set softtabstop=4 softtabstop and sts are equivalent: :set sts=4 Tabs To use tabs as indents, 4 spaces wide: :set noexpandtab :set tabstop=4 tabstop and ts...

vim • Vim Options

ngModel on input[type=text]

AngularJS code for two-way binding on a text input: <input ng-model="ScopePropertyX" type="text" /> KnockoutJS equivalent: <input data-bind="textInput: ScopeObservableX" type="text" />

knockout.js • Equivalents of AngularJS bindings

Implementing text-to-speech

A good example of a feature that request platform specific code is when you want to implement text-to-speech (tts). This example assumes that you are working with shared code in a PCL library. A schematic overview of our solution would look like the image underneath. In our shared code we define...

Xamarin.Forms • Accessing native features with DependencyService

Laravel 5 App on Shared Hosting on Linux Server

By default Laravel project's public folder exposes the content of the app which can be requested from anywhere by anyone, the rest of the app code is invisible or inaccessible to anyone without proper permissions. After developing the application on your development machine, it needs to be pushed t...

Laravel • Deploy Laravel 5 App on Shared Hosting on Linux Server

A very simple Hello World application

Starting from a fresh installation of Codeigniter 3, here is a simple way to start with an Hello World application, to break the ice with this solid PHP framework. To do this you can start creating the view that we want to be shown for our Hello World app. We are going to put it in your applicatio...

codeigniter • Let's start: Hello World

Let's use the controller a little more

Now we'll try going for a little more complex example, using the capabilities of the controller to fill in the view. Here is our view: /application/views/hello_world.php <!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <titl...

codeigniter • Let's start: Hello World

Let's choose our greetings: Hello World or Good Bye World or ...?

Let's say that we want to have an alternative greeting that is accessible through a different URL. We might create a new function or even a new controller for that, but a best practice is to optimize what we already have, to make it work at it's best! To do this, we'll keep the same view as in the ...

codeigniter • Let's start: Hello World

Using collection initializer inside object initializer

public class Tag { public IList<string> Synonyms { get; set; } } Synonyms is a collection-type property. When the Tag object is created using object initializer syntax, Synonyms can also be initialized with collection initializer syntax: Tag t = new Tag { Synonyms = new List&...

C# Language • Collection Initializers

Recursively describe an object structure

Recursion is when a method calls itself. Preferably it will do so until a specific condition is met and then it will exit the method normally, returning to the point from which the method was called. If not, a stack overflow exception might occur due to too many recursive calls. /// <summary>...

C# Language • Recursion

Write Data to a File

To write the contents of a string to a file: Dim toWrite As String = "This will be written to the file." System.IO.File.WriteAllText("filename.txt", toWrite) WriteAllText will open the specified file, write the data, and then close the file. If the target file exists, it is ...

Visual Basic .NET Language • File Handling

Read All Contents of a File

To read the contents to a file into a string variable: Dim fileContents As String = System.IO.File.ReadAllText("filename.txt") ReadAllText will open the specified file, read data to the end, then close the file. To read a file, separating it into an array element for each line: Dim f...

Visual Basic .NET Language • File Handling

Automatic package installation on emacs start-up

;; package.el is available since emacs 24 (require 'package) ;; Add melpa package source when using package list (add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/") t) ;; Load emacs packages and activate them ;; This must come before configurations o...

emacs • Package Management

Basic Routes

Routes in Flask can be defined using the route decorator of the Flask application instance: app = Flask(__name__) @app.route('/') def index(): return 'Hello Flask' The route decorator takes a string which is the URL to match. When a request for a URL that matches this string is receive...

Flask • Routing

Create PDF

UIGraphicsBeginPDFContextToFile(fileName, CGRectZero, nil); UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 612, 792), nil); [self drawText]; UIGraphicsEndPDFContext(); fileName is the document file where You are going to append or attach NSString* temporaryFile = @"firstI...

iOS • PDF Creation in iOS

Multiple page PDF

UIGraphicsBeginPDFContextToFile(fileName, CGRectZero, nil); UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 600, 792), nil); UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 600, 792), nil); UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 600, 792), nil); ...

iOS • PDF Creation in iOS

Simple WCF service

Minimal requirements for WCF service is one ServiceContract with one OperationContract. Service contract: [ServiceContract] public interface IDemoService { [OperationContract] CompositeType SampleMethod(); } Service contract implementation: public class DemoService : IDemoService...

wcf • Getting started with wcf

Terms

On a very high level, Prolog only has a single data type, called term. In Prolog, all data is represented by Prolog terms. Terms are defined inductively: an atom is a term. Examples of atoms are: x, test and 'quotes and space'. a variable is a term. Variables start with an uppercase letter or un...

Prolog Language • Data Structures