Nested has many through in Rails 3.1

04 May 2012 - Bangalore, India

There’s a cool feature implemented in Rails 3.1. You can now have a nested “has many through” relationship. Here’s an example to show what I mean by a “nested hmt”:

class User < ActiveRecord::Base
  has_many :memberships
  has_many :organizations, :through => :memberships

  # => This is not possible in Rails < 3.1
  has_many :deals, :through => :organizations

 def has_deals?
   self.deals.any?
 end
end

As you can see, organizations table here acts as the join table between users and deals, although users has a has many relationship with organizations through memberships. This nifty feature is very useful when dealing with complex relationships and you don’t have to simulate the “has many through” here.