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Getting started with Ruby on Rails: Build a web app with Ruby

Feb 05, 2021 - 10 min read
Amanda Fawcett

Ruby on Rails (often called Rails) is an open-source, web application development framework written in the Ruby programming language. Rails makes it fun and easy to program web applications: it allows you to write less code but accomplish more than most frameworks.

The Rails framework is opinionated, so it operates on the assumption that there’s a “best” way to make things. In this tutorial, we will introduce you to Rails and show you how to make a web application.

To be most successful, you should already have some knowledge of Ruby, web development languages (HTML, CSS, and JavaScript) and object-oriented programming (OOP).

This tutorial at a glance:

Learn how to build complex Ruby applications

In this course, you will learn the fundamentals of Ruby on Rails to build your own application. By the end, you’ll be able to build complex applications.

Introduction to Ruby on Rails

What is Rails?

Rails is a powerful, extremely opinionated, full-stack web application framework build on top of the back-end Ruby programming language. It is used to build powerful web apps quickly due to its innovative functionalities, such as table migrations and scaffolds.

Rails offers a default structure to organize your code and make workflow easier. Programmers who use Rails say that is makes software development far more fun and simple.


Rails development is based on the Model-View-Controller ( MVC) architecture to organize application programming and is guided by the Don’t Repeat Yourself (DRY) principle of software development.

Rails still remains popular in the world of web app development. Rails is very mature framework with tons of active support. Tons of companies are looking for talented Rails developers, since this framework minimizes app production time.

Some of the big companies who use Rails include AirBnB, GitHub, Basecamp, Shopify, Soundcloud, and Goodreads. It is also popular amongst many startups due to speed.

Facts: The average base salary for a Rails developer is $116,437 USD.

Salient features of Rails

Anyone can learn Rails, even if you have limited experience with Ruby code. Rails is full-stack and offers many integrated tools for rapidly creating dynamic applications. Here are some of the salient features that make Rails so powerful:

  • Automated Testing: Rails provides built-in testing, so test cases are easier to write and execute.
  • Scaffolding: This allows you to easily create models that manage data, views that enable user-data interaction, and controllers that manage model-view communication.
  • Active Record: Rails operates on the assumption that you should ensure data access logic as part of the object to educate users on how to read and write to the database. Objects carry persistent data and behavior that operates on that data.
  • Rails Community: Rails has a very active and involved community, and it’s there are regular fixes and updates.
  • Convention over Configuration: Rails believes that convention is more important than configuration. The framework actually makes decisions for you to boost productivity.

Anatomy of a Rails project

To get more familiar with Rails before building our own app, let’s look at a summary of the standard file and directory structure of any Rails application.

  • app/: contains core application code (controllers, models, views, helpers, mailers, channels, jobs, and assets)

  • bin/: contains binary executable files (scripts) to start, update, deploy, or run your Rails app

  • config/: contains the configuration files for the application, routes, database, etc.

  • db/: contains database files, database schema, and database migrations

  • lib/: contains extended library modules

  • log/: contains the application log files

  • public/: contains data that is accessible via browsers (static files, compiled assets, error pages, etc.)

  • storage/: contains active storage files

  • test/: contains application unit tests, fixtures, and various other test apparatus

  • tmp/: contains temporary files (like cache and pid files)

  • vendor/: contains any third party code

  • Gemfile: contains the gem requirements for the application, required for Ruby to run the app

  • Gemfile.lock: contains a list of gems to ensure all copies of the application use the same version

  • Rakefile: allows the command line to locate and run rake tasks (a Make-like build utility implemented in Ruby for task automation)

  • config.ru: contains configuration for the Rack middleware based servers used to start the application

  • package.json: allows you to specify npm dependencies for your Rails app

How to create your first Rails application

If you don’t have it already, you’ll need to install Rails. First check that your system has the following prerequisites:

  • Ruby
  • SQLite3
  • Node.js
  • Yarn Once you’re good to go on those, install Rails using the gem install command provided by RubyGems.
$ gem install rails

Then, verify that everything is installed correctly by running the following:

$ rails --version

It should say something along the lines “Rails 6.0.0”. Now you’re good to create a project.

New Generator

Rails comes with built-in scripts called generators that automatically create everything you need to start a new project. To create a new application, you invoke the new generator.

Think of this as the foundation for your whole project. The new generator sets up a project in the my_project directory with an application structure.

To use the new generator, we run this command:

rails new my_project

Now you should have an application. We now use the Rails script to run the Puma web-server, which will deploy our Rails application. We cd into the project folder and run the following command:

rails server

You can also run the server with additional parameters.

Keep the learning going.

Learn Ruby on Rails without scrubbing through videos or documentation. Educative’s text-based courses are easy to skim and feature live coding environments - making learning quick and efficient.

Introduction to Ruby on Rails

MVC and Rails: Hello World

Let’s get Rail to say “Hello”. To do this, we need to create a view, route, and controller with an action. Routes will map a request to our controller action. A controller action handles the request and prepares the data for our view. The view simply displays our data in the format we want it.

These features are part of Rails’ MVC design pattern.

MVC is a design pattern that separates the program logic into three elements: models, views, and controllers. This separates the application data and the code. Rails places almost the entire model, view, and controller logic on the server-side.

Syntax: Routes are rules written in a Ruby DSL (Domain-Specific Language). Controllers are essentially just Ruby classes. Any public methods are actions. Views are templates in a HTML and Ruby.

First, we create a customer controller and a view. To make a new controller, we run the controller generator script in the project root directory of my_project/:.

rails generate controller Hello index

This creates a controller called Hello and an action called index.

Our controller is located here: app/controllers/hello_controller.rb and our view is located here app/views/welcome/index.html.erb.

Embedded Ruby

The .erb extension above means that the file is written in Embedded Ruby, which is the default for view templates.

In your html.erb files, you can use tags to embed Ruby code into HTML.

  • <% %>: You can insert any Ruby code between these tags, and the result will not be inserted into your HTML. This is used for control flow statements.
  • <%= %>: Ruby code between this tag gets inserted into the HTML at its position. This is used to retrieve data from models.

Configure views and routes

In the index.html.erb file, we add the line:

<h2>Hello World on Rails!</h2>

This is what will be displayed on the application’s root page /. However, if we run the app now, we will go the old page because the root is currently occupied by a page created when we started the program.

To change this, we make changes to our config/routes.rb file. Essentially, we have to tell the file where the new home page is located.

Your routing file will connect URLs to our code and create paths from your code.

The general syntax for defining a route is as follows:

HTTP_method 'controller_name/action_name'

For our purposes, the controller_name is hello, and our action_name is index. Here is an example f a GET request.

get 'hello/index'

But, we are defining the root of our Rails application, so our syntax is different.

root 'hello#index'

Browsers make requests to the Rails application using HTTP methods (GET, PUT, POST, PATCH, and DELETE). Each of these HTTP methods requests to perform an operation on your application.

So, our routes.rb will be as follows:

Rails.application.routes.draw do
get 'hello/index'
root 'hello#index'
# For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html

Now, when we run the application, it will display our desired “Hello World on Rails!” message.

Models and active records

Rails Model is a Ruby class that for adding database records. Generally, a models should provide four basic functionalities:

  • Create: The ability to add data to record
  • Read: The ability to find some particular data already stored in the database
  • Update: The ability to modify some existing data
  • Delete: The ability to remove data

These functionalities represent the acronym CRUD.

Rails also uses the Active Record framework for creating and using our models. This is an Object Relational Mapping (ORM) framework to connect objects of an application with tables in a relational database management system (RDBMS).

Active Record means we don’t need to write SQL statements directly, so storage and retrieval of properties is much easier.

Think of this as an interface between your database tables and the Ruby code.

Conventions for the Active Record

The naming convention for the Active Record is as follows:

  • Model/Class: singular with the first letter of each word capitalized (ex. SaleItem)
  • Table/Schema: Plural with underscores separating words (ex. sale_items)

Let’s apply this to our app. Suppose you are building a Pet store application. We need to store details for each pet (such as name and age). We need a database and a model.

Let’s create a new pet_store application to understand CRUD better.

rails new pet_store

To create a new model, the syntax is:

rails generate model ModelName ColumnName:ColumnType ColumnName:ColumnType

Now we run the command to generate a new model inside the project folder we made:

rails generate model Pet name:string age:string

This generates two files:

  • db/migrate/<date_time>_create_pets.rb: the migration file
  • app/models/pet.rb: file for your model

Next steps for your learning

Congrats on making it to the end! You should now have the foundations to create your own Ruby on Rails applications. There is still a lot to learn. The next steps are to understand:

  • Migrations in Rails
  • Model structure
  • Comments structure
  • Testing with Rails

To get hands-on practice with these, check out Educative’s course Introduction to Ruby on Rails. You will learn the fundamentals of Ruby on Rails and start by learning how to create a new project, deploy to a Rails server, and the Rails design pattern. After that, you’ll learn how to perform CRUD operations, handle user authentication, and manage sessions.

By the end, you’ll be able to build complex Rails applications and add this skill to your portfolio.

Happy learning!

Continue reading about web applications and Rails

WRITTEN BYAmanda Fawcett

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