RailsTips.org

Delegate is a pretty sweet method. Have you used it yet? Let’s say you have:

class User < ActiveRecord::Base
  has_many :actions
end

class Action < ActiveRecord::Base
  belongs_to :user

  class << self
    def inbox
      find(:all, :conditions => ['inbox = 1'])
    end
  end
end

To access a users inbox actions you would have to:

user = User.find(1)
user.actions.inbox

This isn’t bad, but let’s throw delegate into the mix like so:

class User < ActiveRecord::Base
  has_many :actions

  delegate :inbox, :to => :actions
end

class Action < ActiveRecord::Base
  belongs_to :user

  class << self
    def inbox
      find(:all, :conditions => ['inbox = 1'])
    end
  end
end

Now you can access a user’s inbox actions like this:

user = User.find(1)
user.inbox # instead of user.actions.inbox

Just like the title of this article, the User model says I don’t feel like dealing with the inbox method so why don’t you deal with it Action. Saves some keystrokes and it just feels right.

Related Reads

• Delegation and Demeter in Rails
• Law of Demeter, or How to avoid coding yourself into a corner in Rails
• Law of Demeter and Forwardable
• Law of Demeter