Getting started with ruby-on-rails-3

Remarks#

This section provides an overview of what ruby-on-rails-3 is, and why a developer might want to use it.

It should also mention any large subjects within ruby-on-rails-3, and link out to the related topics. Since the Documentation for ruby-on-rails-3 is new, you may need to create initial versions of those related topics.

Installating Rails on mac.

You would need to install ruby before you can install rails.

Mac already comes with ruby installed based on how recent your macOS is? Depending on what ruby version you want for your development, the best way to install Ruby is to use RVM. In your terminal, type the command below listed in steps:

Install rvm

curl -sSL https://get.rvm.io | bash -s stable --ruby

For Rails 3, best version to install is ruby 1.9.3
```
rvm install 1.9.3
ruby -v #=> 1.9.3 
```
Set your Ruby version
```
rvm use 1.9.3 --default
```
Install Rails (this rails version requires ruby-version >=1.9.3)
```
gem install rails -v 4.2.7.1
rails -v #=> 4.2.7.1
```

Install rails app

rails new my_first_app #(this will install the app for you.)
cd my_first_app
rails s #(run the server)

Open the browser and type below in your URL.
```
https://localhost:3000
```
Message saying ‘Welcome to rails’ will be displayed or similar.

Hello World in Rails

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
```
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>
```
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, https://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
```
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 https://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).
Yay, now the moment of truth. Launch web server after restarting your rails server and navigate to https://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!