Tutorial by Examples: t

Use a dict of functions

Another straightforward way to go is to create a dictionary of functions: switch = { 1: lambda: 'one', 2: lambda: 'two', 42: lambda: 'the answer of life the universe and everything', } then you add a default function: def default_case(): raise Exception('No case found!') ...

Python Language • Alternatives to switch statement from other languages

Use class introspection

You can use a class to mimic the switch/case structure. The following is using introspection of a class (using the getattr() function that resolves a string into a bound method on an instance) to resolve the "case" part. Then that introspecting method is aliased to the __call__ method to ...

Python Language • Alternatives to switch statement from other languages

Using a context manager

Another way, which is very readable and elegant, but far less efficient than a if/else structure, is to build a class such as follows, that will read and store the value to compare with, expose itself within the context as a callable that will return true if it matches the stored value: class Switc...

Python Language • Alternatives to switch statement from other languages

Differences between inner/outer joins

SQL has various join types to specify whether (non-)matching rows are included in the result: INNER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN (the INNER and OUTER keywords are optional). The figure below underlines the differences between these types of joins: the blue area repres...

SQL • JOIN

Label with bindable collection of Spans

I created custom label with wrapper around FormattedText property: public class MultiComponentLabel : Label { public IList<TextComponent> Components { get; set; } public MultiComponentLabel() { var components = new ObservableCollection<TextComponent>(); ...

Xamarin.Forms • Creating custom controls

Performing an action on a view

It is possible to perform ViewActions on a view using the perform method. The ViewActions class provides helper methods for the most common actions, like: ViewActions.click() ViewActions.typeText() ViewActions.clearText() For example, to click on the view: onView(...).perform(click()); onVi...

Android • Testing UI with Espresso

Finding a view with onView

With the ViewMatchers you can find view in the current view hierarchy. To find a view, use the onView() method with a view matcher which selects the correct view. The onView() methods return an object of type ViewInteraction. For example, finding a view by its R.id is as simple as: onView(withId(...

Android • Testing UI with Espresso

Bulkification

If you do row-by-row processing in Salesforce, you'll probably reach the governor limit quickly. This is especially true with triggers and things that fire when you don't expect them. One documented method of escaping the governor limit is bulkification. Note: The following information is based on ...

Salesforce • Trigger Bulkification

Inheritance Modifiers (on classes)

Inherits Specifies the base (or parent) class Public Class Person End Class Public Class Customer Inherits Person End Class 'One line notation Public Class Student : Inherits Person End Class Possible objects: Dim p As New Person Dim c As New Customer Dim s As New Student ...

Visual Basic .NET Language • OOP Keywords

Inheritance Modifiers (on properties and methods)

Overridable Allows a property or method in a class to be overridden in a derived class. Public Class Person Public Overridable Sub DoSomething() Console.WriteLine("Person") End Sub End Class Overrides Overrides an Overridable property or method defined in the base...

Visual Basic .NET Language • OOP Keywords

Interfaces

Public Interface IPerson Sub DoSomething() End Interface Public Class Customer Implements IPerson Public Sub DoSomething() Implements IPerson.DoSomething Console.WriteLine("Customer") End Sub End Class

Visual Basic .NET Language • OOP Keywords

Installation or Setup

Chart.js can be included in several different ways: NPM Run the following command on your NPM project directory npm install chart.js --save CDN Include a script tag in your HTML linking to the chart.js CDN <html> <body> <script type="text/javascript" s...

chart.js • Getting started with chart.js

Using character constants instead of string literals, and vice versa

In C, character constants and string literals are different things. A character surrounded by single quotes like 'a' is a character constant. A character constant is an integer whose value is the character code that stands for the character. How to interpret character constants with multiple charac...

C Language • Common pitfalls

How to know the directory and/or the path of the file you are editing

To know the path of the directory your file is in you can use: Esc to enter command mode :pwd This will print the path to the directory at the bottom of the editor, like this I'm a ninja ~ ~ ~ ~ ~ /home/ubuntu/myfolder 1,5 All Now...

vim • Tips and tricks to boost productivity

SQLite

SQLite is a lightweight, disk-based database. Since it does not require a separate database server, it is often used for prototyping or for small applications that are often used by a single user or by one user at a given time. import sqlite3 conn = sqlite3.connect("users.db") c = con...

Python Language • Database Access

Download a file from Server using Retrofit2

Interface declaration for downloading a file public interface ApiInterface { @GET("movie/now_playing") Call<MovieResponse> getNowPlayingMovies(@Query("api_key") String apiKey, @Query("page") int page); // option 1: a resource relative to your bas...

Android • Retrofit2

Sample to get user profile path

# will retrieve my home path ENV['HOME'] # => "/Users/username" # will try retrieve the 'FOO' environment variable. If failed, will get 'bar' ENV.fetch('FOO', 'bar')

Ruby Language • Environment Variables

Introduction

Ruby has three types of objects: Classes and modules which are instances of class Class or class Module. Instances of classes. Singleton Classes. Each object has a class which contains its methods: class Example end object = Example.new object.class # => Example Example.class # ...

Ruby Language • Singleton Class

Accessing Singleton Class

There are two ways to get singleton class of an object singleton_class method. Reopening singleton class of an object and returning self. object.singleton_class singleton_class = class << object self end

Ruby Language • Singleton Class

Accessing Instance/Class Variables in Singleton Classes

Singleton classes share their instance/class variables with their object. class Example @@foo = :example end def Example.foo class_variable_get :@@foo end Example.foo #=> :example class Example def initialize @foo = 1 end def foo @foo end end e = Ex...

Ruby Language • Singleton Class