We were discussing how to improve the following code on the #ror_au channel today:

class Category < ActiveRecord::Base

  def self.simple_options(id)

    options = Option.find(

                     :all,

                     :conditions => ["category_id = ?",id],

                     :order => "sort")

    return_options = []

    for o in options

      return_options << o if o.in_simple == 1

    end

    return return_options

  end

end

First, simple_options is a class method, but is always called within the context of a single category. This is achieved in the code above by passing a category id to the class method, but in OO languages we typically achieve this through the use of an instance method:

class Category < ActiveRecord::Base

  def simple_options

    options = Option.find(

                     :all,

                     :conditions => ["category_id = ?",id],

                     :order => "sort")

    return_options = []

    for o in options

      return_options << o if o.in_simple == 1

    end

    return return_options

  end

end

Given that the condition on the find is scoping the options to a category, we can use an association to handle the scoping for us:

class Category < ActiveRecord::Base

  has_many :simple_options, :class_name => "Option", 

    :order => :sort

end

Now we're missing the further scoping handled by the for loop that prunes the result set down to those records where in_simple == 1, so let's add a condition.

class Category < ActiveRecord::Base

  has_many :simple_options, :class_name => "Option", 

    :order => :sort, :conditions => "in_simple = 1"

end

There, isn't that nicer. But the subject of this post is association *extensions* which I haven't touched on yet. Given that there's a second class method for Category, self.advanced_options, we can use association extensions to our advantage to scope simple_options, and advanced_options to a single association:

class Category < ActiveRecord::Base

  has_many :options, :order => :sort do

    def that_are_simple

      find(:all, :conditions => "in_simple = 1")

    end

    def that_are_advanced

      find(:all, :conditions => "in_advanced = 1")

    end

  end 

end

So now for any instance of a Category we can refer to options.that_are_simple, and options.that_are_advanced. Doesn't that make you feel all warm and fuzzy inside.

Nathan de Vries wrote a script today that lists all supported Rails::Configuration options that are available for customisation in your Rails::Initializer block. Very handy if you don't want to have to dig through the source to find what options are available.

Thanks Nathan!