I have four models question, answer, comment and vote.Consider it same as stackoverflow.

1. Question has_many comments
2. Answers has_many comments
3. Questions has_many votes
4. answers has_many votes
5. comments has_many votes

Here are the models (only relevant things)

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true
  has_many :votes, :as => :votable, :dependent => :destroy
end

class Question < ActiveRecord::Base  
    has_many :comments, :as => :commentable, :dependent => :destroy
    has_many :answers, :dependent => :destroy
    has_many :votes, :as => :votable, :dependent => :destroy
end

class Vote < ActiveRecord::Base
   belongs_to :votable, :polymorphic => true
end


class Answer < ActiveRecord::Base
    belongs_to :question, :counter_cache => true
    has_many :comments, :as => :commentable , :dependent => :destroy
end

Now the problem is whenever i am trying to delete any question/answer/comment its giving me an error

  NoMethodError in QuestionsController#destroy
   undefined method `each' for 0:Fixnum

if i remove this line from any of the model (question/answer/comment)

   has_many :votes, :as => :votable, :dependent => :destroy

then it works perfectly. It seems there is a problem while deleting the records active record is not able to find out the proper path because of multiple joins within the tables.