loading...

Delegate in Rails

neshaz profile image Nesha Zoric ・1 min read

A model should only talk to its immediate association. According to the Law of Demeter, you shouldn’t talk to the association’s property or association’s association.

Here we talk about Rails delegate approach.

BAD SMELL

class Profile < ActiveRecord::Base
belongs_to :user
end

<%= @profile.user.address %>
<%= @profile.user.city %>

Rails provides helper method to accomplish delegation, which uses DSL to generate wrapper methods. It can also prevent error call method on nil object if :allow_nil => true is added.

Refactored

class Profile < ActiveRecord::Base
  belongs_to :user
  delegate :address, :city, :to => :user, :prefix => true, :allow_nil => true
end
<%= @profile.user_address %>
<%= @profile.user_city %>

Originally published at Kolosek blog.

Posted on by:

neshaz profile

Nesha Zoric

@neshaz

Founder/CTO at Kolosek. Building tech startups. Starting project? Contact at https://kolosek.com

Discussion

pic
Editor guide