Code snippet showing how to search for polymorpic related Rails Active Record relying on Rails 4 SQL duct typing magic!

rails_4_polymorphic_where_power

class Post < ActiveRecord::Base
  has_many :comments, as: commentable
  
  # attributes, :title
end

class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
end


post = Post.create! title: 'new_post'
comment = post.comments.create

Comment.where(commentable: post) 
                                    # In Rails 3.2.12, this did not return the instantiated Post object, 
                                    # but in Rails 4, this does return the Post instance