rails-getting-started.md

Getting started with Rails

Ruby on Rails is a so called framework, which means that it contains commonly used functions so you can focus on building the custom parts of the application.

Install rails if you don't have it already

Open a terminal and type

rails -v

If you get something similar, you're good to go:

Rails 5.2.0

If not, you can install rails using the gem command:

gem install rails

Create a new rails project

Most of the time when you start a Rails project you'll use the code generation feature of the framework. Easily type:

rails new blog

This will create a new rails project named blog into a new folder called blog.

This will take a few seconds. After it's finished check out the blog folder: a lot of files and folders are generated for you. Most of the files are empty. The main point is that the structure of the application is generated. Since most Rails apps are created this way every time you start working on a Rails project you'll already know where to find certain files.

Let's fire up the web app!

cd blog
ruby bin/rails server

Rails comes with a built-in webserver so you don't have to worry about setting up your own. The server starts on your computer, and you'll be able to access it from a browser through http://localhost:3000. Here localhost means your own computer. You should see the default Rails greeting page.

Look around

Open the blog folder in VS Code.

There are quite a few folders here, but you don't have to worry about them, we'll use only some of them:

• The app folder contains your applications code, and
• The config folder contains configurations for the server

Ignore the other folders for now.

Open the app folder, this is where we'll spend most of our time.

The views folder contains files related to presentation, mostly HTML and CSS, you are already familiar with these.

The controllers folder contains your Controllers which are responsible of handling HTTP requests.

The models folder contains the Models which represents the data in your application.

Ignore the other folders for now.

Home page

So our app is pretty much empty; let's create a simple home page!

First let's create the presentation for the page, which should go under the views/home folder; therefore, create a new folder called home under views and a new file called index.html.erb:

<h1>My own blog</h1>
<p>This is the home page</p>

We'll add details later.

To handle incoming requests let's create a new file called home_controller.rb under controllers named HomeController.

class HomeController < ApplicationController
    def index
    end
end

A class is basically just a bunch of methods and variables grouped together.

Finally, let's tell Rails that this is our home page. Open /config/routes.rb and add the following line to the middle of the file.

root 'home#index'

This will tell Rails that the root page (which is the home page) is handled by the HomeController's index action. An action is basically a function of a controller.

Now if you refresh your page in the browser you should see your own content.

View: HTML with benefits

You probably noticed that the view files have .html.erb extension, which is kind of strange at first. These are generally HTML files, as the name suggests, but you can also include Ruby code in them. (.erb stands for Embedded Ruby)

Try something like this in index.html.erb:

<p>
    <%= 3 + 2 %>
</p>

Refreshing the page you'll find 5 printed out. So as you can see, wherever you need Ruby you can add <%= ruby code %> and it will be interpreted as Ruby code.

Of course you'll want to minimize the Ruby code in the View layer as it's main purpose is presentation, so usually you won't find calculations in these files.

Instead, you should use the Controller.

Let's change the HomeController:

def index
    @result = 2 + 3
end

And change the view accordingly:

<p>
    <%= @result %>
</p>

The at sign (@) before the variable result means that the variable is accessible outside of the function; therefore, it is accessible from the view as well.

This is the common way of splitting application code: do every calculation in the controller and use variables to pass data to the view.