ruby-on-rails-3 Getting started with ruby-on-rails-3 Hello World in Rails

Example

1. Say "Hello", Rails

   To get Rails saying "Hello", you need to create at minimum a controller and a view.

   A controller's purpose is to receive specific requests for the application. Routing decides which controller receives which requests. Often, there is more than one route to each controller, and different routes can be served by different actions. Each action's purpose is to collect information to provide it to a view.

   A view's purpose is to display this information in a human readable format. An important distinction to make is that it is the controller, not the view, where information is collected. The view should just display that information. By default, view templates are written in a language called eRuby (Embedded Ruby) which is processed by the request cycle in Rails before being sent to the user.

   To create a new controller, you will need to run the "controller" generator and tell it you want a controller called "Welcome" with an action called "index", just like this:

   $ bin/rails generate controller Welcome index
   

   Rails will create several files and a route for you.

   create  app/controllers/welcome_controller.rb
    route  get 'welcome/index'
   invoke  erb
   create    app/views/welcome
   create    app/views/welcome/index.html.erb
   invoke  test_unit
   create    test/controllers/welcome_controller_test.rb
   invoke  helper
   create    app/helpers/welcome_helper.rb
   invoke  assets
   invoke    coffee
   create      app/assets/javascripts/welcome.coffee
   invoke    scss
   create      app/assets/stylesheets/welcome.scss
   

2. Most important of these are of course the controller, located at app/controllers/welcome_controller.rb and the view, located at app/views/welcome/index.html.erb.

   Open the app/views/welcome/index.html.erb file in your text editor. Delete all of the existing code in the file, and replace it with the following single line of code:

   <h1>Hello, Rails!</h1>
   

3. Now that we have made the controller and view, we need to tell Rails when we want "Hello, Rails!" to show up. In our case, we want it to show up when we navigate to the root URL of our site, http://localhost:3000.

   Next, you have to tell Rails where your actual home page is located.Edit the file by adding the line of code root 'welcome#index'. It should look something like the following:

   Rails.application.routes.draw do
     get 'welcome/index'
   
     root 'welcome#index'
   end
   

4. root welcome#index tells Rails to map requests to the root of the application to the welcome controller's index action and get welcome/index tells Rails to map requests to http://localhost:3000/welcome/index to the welcome controller's index action. This was created earlier when you ran the controller generator (bin/rails generate controller Welcome index).

5. Yay, now the moment of truth. Launch web server after restarting your rails server and navigate to http://localhost:3000 in your browser. You'll see the "Hello, Rails!" message you put into app/views/welcome/index.html.erb, indicating that this new route is indeed going to WelcomeController's index action and is rendering the view correctly.

This Guide is from guides.rubyonrails.org. Happy Hacking!