freeCodeCamp/guide/english/ruby/ruby-on-rails/index.md

title
Ruby on Rails

Ruby on Rails

Ruby on Rails is a server-side framework (gem) built on the Ruby language to make progressive web applications and APIs. Rails makes web development faster, easier and more fun. It includes everything you need to build fantastic applications and has a big community. Rails was created by David Heinemeir Hansson and is currently on it's 5th version. Rails emphasizes the use of other well-known software engineering patterns and paradigms, including convention over configuration (CoC), don't repeat yourself (DRY), and the active record pattern. Rails is a model–view–controller (MVC) framework, providing default structures for a database, a web service, and web pages. Lately, Rails has integrated an API module to make the creation of web-services faster and easier.

Installing Rails

Rails is downloaded in the same way as any other Ruby gem: with the gem install command. Before we download it, we'll need to download Ruby. Afterwards we're only 3 words away from starting with Ruby on Rails:

$ gem install rails

Setting Up database

Rails ships with sqlite3 as the default database, which is a simple file on disk. You need to install MySQL or PostgreSQL if you want to use something more robust. Ruby on Rails can also be configured to use NoSQL databases like Couchbase and MongoDB but that may have some additional manual steps.

Creating a Rails application

1. After you install Ruby on Rails, it's very simple to create a brand new application, we'll just need 3 more words:

$ rails new your_application_name

• If you want to use MySQL

$ rails new <application_name> -d mysql

• If you want to use Postgres

$ rails new <application_name> -d postgresql

2. This command will create a folder with the your_application_name you informed in the last command. Next step is to go to the new directory you've just created:

$ cd your_application_name

3. Get the necessary gems and software packages before running your application:

$ bundle install

4. To run the rails server and see if everything went accordingly is also fast:

$ rails server

It couldn't be anymore simple! Well, this isn't actually 100% true, we could make it even smaller by reducing the rails server command to:

$ rails s

5. Now, with your preferred browser, go to http://localhost:3000 and you'll see: "Yay! You’re on Rails!"

Alternative method for creating a Rails application

1. Create a new directory:

   $ mkdir <application_name>
   

2. Go into the new directory:

   $ cd <application_name>
   

3. Create the Rails application using the Unix dot notation. This results in assigning the name of the directory to the new application.

   $ rails new .
   

4. Start exploring the framework of the application you just created. The folder structure is organized according to the table below:

File/Folder	Purpose
app/	Contains the controllers, models, views, helpers, mailers, channels, jobs and assets for your application. You'll focus on this folder for the remainder of this guide.
bin/	Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy or run your application.
config/	Configure your application's routes, database, and more. This is covered in more detail in Configuring Rails Applications.
config.ru	Rack configuration for Rack based servers used to start the application.
db/	Contains your current database schema, as well as the database migrations.
Gemfile, Gemfile.lock	These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see the Bundler website.
lib/	Extended modules for your application.
log/	Application log files.
public/	The only folder seen by the world as-is. Contains static files and compiled assets.
Rakefile	This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing Rakefile, you should add your own tasks by adding files to the lib/tasks directory of your application.
README.md	This is a brief instruction manual for your application. You should edit this file to tell others what your application does, how to set it up, and so on.
test/	Unit tests, fixtures, and other test apparatus. These are covered in Testing Rails Applications.
tmp/	Temporary files (like cache and pid files).
vendor/	A place for all third-party code. In a typical Rails application this includes vendored gems.
.gitignore	This file tells git which files (or patterns) it should ignore. See GitHub - Ignoring files for more info about ignoring files.

A great place to getting started with this awesome framework is reading his Getting Started page.

Convention over Configuration

Convention over Configuration means a developer only needs to specify unconventional aspects of the application. For example, if there is a class Sale in the model, the corresponding table in the database is called sales by default. It is only if one deviates from this convention, such as calling the table "products sold", that the developer needs to write code regarding these names. Generally, Ruby on Rails conventions lead to less code and less repetition.

What is MVC?

Model (Active record) contains the business logic and interacts with the database. Views (Action views) all of the HTML files and structure. Controller (Action controller) interacts with the views and model to direct the actions of the application.

DRY - Don't Repeat Yourself

Don't repeat yourself means that information is located in a single, unambiguous place. For example, using the ActiveRecord module of Rails, the developer does not need to specify database column names in class definitions. Instead, Ruby on Rails can retrieve this information from the database based on the class name.

Ruby on Rails is open source

Not only is it free to use, you can also help make it better. More than 4,500 people have already contributed code to Rails. It’s easier than you think to become one of them.

Famous websites use or used Ruby on Rails

Twitter was originally written in Ruby on Rails but moved away to a Java-based framework when needing to scale more. Twitch also heavily used Ruby and Ruby on Rails in the early stages but moved certain parts to Go-lang for anything that needed to be high-performant. Many websites that become famous and popular move parts or all of their back-end systems to frameworks based on compiled languages such Java, C++/C, and Go-lang from dynamic languages Ruby, Python, and Javascript (node). This is not always the case. Certain website are able to make dynamic language frameworks scale to as large as they need. Some good example are GitHub, Gitlab(open-source), Shopify, and Hulu.