ruby on rails - Polymorphic many-to-many relation, correct definition and how to retrieve related models? -

i'm trying build small database handle responsibilities.

different users can responsible different things ("managables")

• projects
• functions
• packages
• documents

a user can responsible n managables, , managable can have n responsibles.

i have following models:

class user < activerecord::base has_many :responsibilities end  class responsibility < activerecord::base belongs_to :managable, :polymorphic => true belongs_to :user end  class project < activerecord::base has_many :responsibles, :as => :managable, :class_name => 'responsibility' , :source_type => "project" end 

i generated models using rails g scaffold user , added relations afterwards, in model.rb files.

i expected able use like:

u = user.new p = project.new r = responsibility.new  r.user = u r.managable = p 

and retrieve responsible each manageable p.responsibles gets me

nomethoderror: undefined method `responsibles' #<responsibility:0x532f1a0> 

it looks me if managable_type column not filled. it's 0.

what missing?