Rails: Many to many polymorphic relationships

Question

See comments for updates.

I\'ve been struggling to get a clear and straight-forward answer on this one, I\'m hoping this time I\'ll get it! :D I definitely have

Answer 1

Although the answer proposed by by SFEley is great, there a some flaws:

• The retrieval of tasks from target (Store/Vehicle) works, but the backwards wont. That is basically because you can't traverse a :through association to a polymorphic data type because the SQL can't tell what table it's in.
• Every model with a :through association need a direct association with the intermediate table
• The :through Assignment association should be in plural
• The :as statement wont work together with :through, you need to specify it first with the direct association needed with the intermediate table

With that in mind, my simplest solution would be:

class Assignment < ActiveRecord::Base
  belongs_to :task
  belongs_to :target, :polymorphic => true
end

class Task < ActiveRecord::Base
  has_many :assignments
  # acts as the the 'has_many targets' needed
  def targets
    assignments.map {|x| x.target}
  end
end

class Store < ActiveRecord::Base
  has_many :assignments, as: :target
  has_many :tasks, :through => :assignment
end

class Vehicle < ActiveRecord::Base
  has_many :assignments, as: :target
  has_many :tasks, :through => :assignment, :as => :target
end

References: http://blog.hasmanythrough.com/2006/4/3/polymorphic-through