MVCHow Rails Applies the Model-View-Controller Pattern to Process Browser Requests

1. User enters URL into browser to generate request
2. Server receives request and sends to router
3. Router matches request type and URL to controller action
4. Controller action renders view
5. Server responds to request

Routes

The purpose of a route is to link a URL to a controller action.

The four components of a route are the:

1. Request method
2. URL pattern
3. Controller and controller action names
4. Name for the URL pattern

The general form of a route is:

[request_method] "[URL]", to: "[controller]#[action]", as: "[name]"

The first part, get ‘welcome’ tells the Rails router to accept GET requests to the URL formed by concatenating the site root (for now http://localhost:3000) with a slash (/) followed by the page-specific path in quotes (welcome).

The to argument tells the router which controller action should be called when it receives such a GET request.
Note that routes use the shorthand “static_pages#welcome” to refer to the method welcome in the StaticPagesController class.

The as argument automatically generates the helper methods welcome_path and welcome_url, which return the relative path and the full URL for this route, respectively.
You should use these helpers in your code instead of hard-coding paths.

For example, the system root could change (e.g., if the app was deployed to Heroku or was running on a port other than 3000), and using these helpers will save you from having to search for and update all the hard-coded URLs spread throughout your code.

Controller

A controller is a ruby class made up of methods, also called actions because they perform actions in response to a server request.
Actions can have three main responsibilities:

1. Act on model objects
2. Render views
3. Redirect to other controller actions

Views

Rails views use the .html.erb extension instead of .html, so they can run embedded ruby code.