Controller Development

This document provides an overview for creating a simple (non-scaffolded) controller with corresponding views and routes.

While it is possible to create a simple controller without any scaffolding, the examples here make use of a Movie model with the following attributes: title (string), year (integer) and seen (boolean). A scaffold can be created for this model to allow for easy entry of movie records. This document describes the creation of a non-scaffolded controller that presents summary information based on the Movie model.

The follow command creates a controller (called report) and two views (called summary and random):

   rails generate controller report summary random

The command does the following:

URL path routes to summary and random are specified in the config/routes.rb file
Creates a report controller in app/controllers. This file contains the summary and random actions, which are defined as ruby methods.
Creates templates for the summary and random views, located in app/views/report.

Each of these items are reviewed in the next sections.

Routes

The routes.rb file (in the config folder) provides rules for parsing a URL (e.g. http://localhost:3000/report/summary) and directing the request to the right controller (e.g. report) and action (e.g. summary). For example, the following line indicates that report/summary is a defined path for the report controller and the summary view for a get request:

   get "report/summary"

Note that the routes.rb file has a line with resources :movies. This one statement creates all of the routes for the scaffolded code created around the Movie model.

Controller

The routing system calls an action (e.g. summary) in a specified controller (e.g. report). Ruby code in the defined action typically interacts with the database and assigns results to instance variables. For example, the following code gets the number of records and a list of records from the movies table (based on the Movie model):

   def summary
      @movie_count = Movie.count
      @movie_list = Movie.all
   end

Unless specified otherwise, the view template with the same name is used to display the results. For example, the summary action will then be displayed with the view summary.html.erb.

Views

Views are located in the app/views folder, organized in subfolders that correspond to the controller name that go with them. In addition to HTML code, they consist of dynamic tags that allow for ruby statements (<% ruby-statements %>) and expressions (<%= ruby-expression %>).

Here is an example of view template code that displays all movie titles as a numbered list:

  <h1>Movie List</h1>

  <ol>
  <% @movie_list.each do |m| %>

    <li> <%= m.title %> </li>

  <% end %>
  </ol>