Rails How to get all the grandchildren of an ojbect.

Question

I have 3 models

User
has_many :quetions
has_many :corrections
end

Question
has_one :correction
belongs_to :user
end

Correction
belongs_to :user
belongs_to :question

So if user Bob asks a question then user Terry can check it and if its wrong offer a correction.

Lets stay with bob and assume he as kindly corrected 5 other users, i.e and lets assume he has been lucky to get 3 corrections from other users.

I want to be able to do something like this

@bob.corrections_offered => 5 correction objects @bob.corrections_received => 3 correction objects

the first one is easy as its really just @bob.corrections under the hood. But i dont know how to implement the latter one. Can anyone help?

UPDATE

SO i tried using through as suggested like so (Oh and actually the question model above is actually called Sentence in my code. I.e. User => Sentence => Correction. )

has_many :sentences
has_many :corrections_received, :through => :sentences, :class_name => 'Correction'

but got this error in console

ctiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :Correction in model Sentence. Try 'has_many :corrections_received, :through => :sentences, :source => '. Is it one of :language, :correction, :user, or :checker?

So tried the following

has_many :corrections_received, :through => :sentences, :source => :correction 

but got

ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_one for has_many :corrections_received, :through => :sentences. Use :source to specify the source reflection.

not sure whats going wrong...

Answer 1

Normally, you should be able to do it with :through, but I'm not sure if two user->correction relationships are possible.

In any case, helper method in the model class should be simple enough. Something like this.

  def corrections_received
    result = Array.new
    questions.each do |q|
      if q.correction
        result.push q.correction
      end
    end
    result
  end

Since I'm new to this stuff, corrections are welcome!

Answer 2

You can add a has_many through relationship in your user model like so

class User
  #your usual relationships
  has_many :corrections_received, :through => :questions, :class_name => 'Correction'
end

Answer 3

try this way: has_many :corrections_received,:class_name=>'Correction',:conditions=>...