A simple example of using Modules with Ruby On Rails

18 July 2011

A module provides a means of grouping together classes, methods and constants.

This is advantageous for two reasons:

It provides a namespace to avoid name clashes.
It allows you to "mixin" the contents of the module into an existing class so that the module functions behave as if they were methods of the class.

Lets see this in action with a simple example:

We create a module called TextStatistics, in a file called text_statistics.rb, which we place in the lib directory.

module TextStatistics
  def word_count
    self.body.scan(/\w+/).size
  end
  
  def letter_count
    self.body.scan(/./).size
  end
end

We can then "mixin" this module into both our classes.

class Article < ActiveRecord::Base
  include TextStatistics
end

class Comment < ActiveRecord::Base
  include TextStatistics
end

allowing us to write code like this

<%= @article.word_count %>

and this

<%= @comment.letter_count %>

shiningthrough