Tutorial by Examples: co

Lexicographical comparison

Two std::strings can be compared lexicographically using the operators ==, !=, <, <=, >, and >=: std::string str1 = "Foo"; std::string str2 = "Bar"; assert(!(str1 < str2)); assert(str > str2); assert(!(str1 <= str2)); assert(str1 >= str2); assert...

C++ • std::string

Basic Component

Given the following HTML file: index.html <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>React Tutorial</title> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.2.1/react.js"></script>...

React • Components

Benefits of Using Composer

Composer tracks which versions of packages you have installed in a file called composer.lock, which is intended to be committed to version control, so that when the project is cloned in the future, simply running composer install will download and install all the project's dependencies. Composer de...

PHP • Composer Dependency Manager

Nesting Components

A lot of the power of ReactJS is its ability to allow nesting of components. Take the following two components: var React = require('react'); var createReactClass = require('create-react-class'); var CommentList = reactCreateClass({ render: function() { return ( <div className...

React • Components

Conditional pattern matching with guards

Patterns can be matched based on values independent to the value being matched using if guards: // Let's imagine a simplistic web app with the following pages: enum Page { Login, Logout, About, Admin } // We are authenticated let is_authenticated = true; // But we aren't admins...

Rust • Pattern Matching

Restarting docker container

docker restart <container> [<container>...] Option --time : Seconds to wait for stop before killing the container (default 10) docker restart <container> --time 10

Docker • Managing containers

Concerns

To avoid repetition in nested routes, concerns provide a great way of sharing common resources that are reusable. To create a concern use the method concern within the routes.rb file. The method expects a symbol and block: concern :commentable do resources :comments end While not creating a...

Ruby on Rails • Routing

List all contributions grouped by author name

git shortlog summarizes git log and groups by author If no parameters are given, a list of all commits made per committer will be shown in chronological order. $ git shortlog Committer 1 (<number_of_commits>): Commit Message 1 Commit Message 2 ... Committer 2 (<number_of_...

Git • Browsing the history

Loop control with break, next, and redo

The flow of execution of a Ruby block may be controlled with the break, next, and redo statements. break The break statement will exit the block immediately. Any remaining instructions in the block will be skipped, and the iteration will end: actions = %w(run jump swim exit macarena) index = 0 ...

Ruby Language • Control Flow

Conditional loop

The for keyword is also used for conditional loops, traditionally while loops in other programming languages. package main import ( "fmt" ) func main() { i := 0 for i < 3 { // Will repeat if condition is true i++ fmt.Println(i) } } play ...

Go • Loops

Unmodifiable Collection

Sometimes it's not a good practice expose an internal collection since it can lead to a malicious code vulnerability due to it's mutable characteristic. In order to provide "read-only" collections java provides its unmodifiable versions. An unmodifiable collection is often a copy of a mod...

Java Language • Collections

Discovering which virtual environment you are using

If you are using the default bash prompt on Linux, you should see the name of the virtual environment at the start of your prompt. (my-project-env) user@hostname:~$ which python /home/user/my-project-env/bin/python

Python Language • Virtual environments

Convention Over Configuration

In Rails, you find yourself looking at controllers, views, and models for your database. To reduce the need for heavy configuration, Rails implements rules to ease up working with the application. You may define your own rules but for the beginning (and for later on) it's a good idea to stick to co...

Ruby on Rails • Rails Best Practices

Thread-safe Collections

By default, the various Collection types are not thread-safe. However, it's fairly easy to make a collection thread-safe. List<String> threadSafeList = Collections.synchronizedList(new ArrayList<String>()); Set<String> threadSafeSet = Collections.synchronizedSet(new HashSet<S...

Java Language • Concurrent Collections

Autosquash: Committing code you want to squash during a rebase

Given the following history, imagine you make a change that you want to squash into the commit bbb2222 A second commit: $ git log --oneline --decorate ccc3333 (HEAD -> master) A third commit bbb2222 A second commit aaa1111 A first commit 9999999 Initial commit Once you've made your change...

Git • Squashing

Configuring router-outlet

Now that the router is configured and our app knows how to handle the routes, we need to show the actual components that we configured. To do so, configure your HTML template/file for your top-level (app) component like so: //app.ts import {Component} from '@angular/core'; import {Router, ROUT...

Angular 2 • Routing (3.0.0+)

Copying a range of commits from one branch to another

git cherry-pick <commit-A>..<commit-B> will place every commit after A and up to and including B on top of the currently checked-out branch. git cherry-pick <commit-A>^..<commit-B> will place commit A and every commit up to and including B on top of the currently checked-out...

Git • Cherry Picking

Generating A Controller

To generate a controller (for example Posts), navigate to your project directory from a command line or terminal, and run: $ rails generate controller Posts You can shorten this code by replacing generate with g, for example: $ rails g controller Posts If you open up the newly generated app/...

Ruby on Rails • Getting started with Ruby on Rails

Remove, delete and cleanup containers

docker rm can be used to remove a specific containers like this: docker rm <container name or id> To remove all containers you can use this expression: docker rm $(docker ps -qa) By default docker will not delete a container that is running. Any container that is running will produce a...

Docker • Managing containers

Reassigning constants

You can't reassign constants. const foo = "bar"; foo = "hello"; Prints: Uncaught TypeError: Assignment to constant.

JavaScript • Declarations and Assignments