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Get up and running quickly by building a Rails app from scratch.

Getting Started

Nice work! You built a working Rails app that displays the Rails default page. How does it work?

<ol>
  <li>The <code>rails new MySite</code> command created a new Rails app named MySite. It generated a number of files and folders that we will use to build the app. In the Code Editor, click on the folder icon to see these files and folders. We'll see what these files and folders are for in the next exercises. The <code>rails new</code> command is the starting point of every Rails project.</li>
  <li>The <code>bundle install</code> command installed all the software packages needed by the new Rails app. These software packages are called gems and they are listed in the file <strong>Gemfile</strong>.</li>
  <li>The <code>rails server</code> command started the Rails development server so that we could preview the app in the browser by visiting <code>http://localhost:4001</code>. This development server is called WEBrick.</li>
</ol>


Hello Rails II

Congratulations! You built a Rails app from scratch. What can we generalize so far?

Using the <a href="https://www.codecademy.com/articles/request-response-cycle-static" target="_blank">request/response cycle</a> as a guide, this has been our workflow when making a Rails app. 

1. Generate a new Rails app. 
2. Generate a _controller_ and add an _action_. 
3. Create a _route_ that maps a URL to the controller action.
4. Create a _view_ with HTML and CSS.
5. Run the local web server and preview the app in the browser.

Generalizations

Well done! Now when a user visits `http://localhost:4001/welcome`, the route

```ruby
get 'welcome', to:'pages#home'
```

will tell Rails to send this request to the Pages controller's `home` action.


Views

Ruby on Rails is a web framework that makes it easy to build powerful web apps in a short amount of time.

Ruby on Rails is written in the Ruby programming language. If you are new to Ruby, we recommend you first take [our Ruby course](https://www.codecademy.com/learn/learn-ruby).



Hello Rails I

Great! We created a new controller named Pages. How did we do this?

1. The `rails generate controller Pages` command generated a new controller named Pages. This created a file named **app/controllers/pages_controller.rb**.
2. Inside the new Pages controller, we added a method called `home`. Methods in Rails controllers are also referred to as controller actions, so here we added the `home` action to the Pages controller.


Routes

What happens when you visit `http://localhost:4001` in the browser? Check out the diagram in the browser by scrolling down to the **How it Works** section.

1. The browser makes a _request_ for the URL `http://localhost:4001`.
2. The request hits the Rails _router_ in **config/routes.rb**. The router recognizes the URL and sends the request to the _controller_.
3. The controller receives the request and processes it.
4. The controller passes the request to the _view_.
5. The view renders the page as HTML. 
6. The controller sends the HTML back to the browser for you to see. 

This is called the **request/response cycle**. It’s a useful way to see how the files and folders of a Rails app fit together.
