ruby on rails - Polymorphic has_many :through NoMethodError: undefined method `klass' for nil:NilClass -
so started setup has_many :through polymorphic association in app. models following:
class song < activerecord::base has_many :collections, through: :collectionitems has_many :collectionitems, through: :collectable end class album < activerecord::base has_many :collections, through: :collectionitems has_many :collectionitems, through: :collectable end class collection < activerecord::base has_many :albums, through: :collectionitems, source: :collectable, source_type: "album" has_many :songs, through: :collectionitems, source: :collectable, source_type: "song" has_many :collectionitems end class collectionitem < activerecord::base belongs_to :collection belongs_to :collectable, polymorphic: true end this allows me following calls:
collection.first.songs => returns array of songs first collection collection.first.albums => returns array of albums first collection collectionitem.first.collection => returns collection collectionitem belongs collectionitem.first.collectable => returns record collectionitem belongs (song or album)
my problem comes when try find collections specific album or song belongs to.
both song.first.collections , album.first.collections return following error when called in rails console.
song.first.collections song load (0.2ms) select "songs".* "songs" order "songs"."id" asc limit 1 nomethoderror: undefined method `klass' nil:nilclass /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `block in source_reflection' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `collect' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `source_reflection' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:579:in `derive_class_name' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:133:in `class_name' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:178:in `klass' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `block in source_reflection' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `collect' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:420:in `source_reflection' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/reflection.rb:557:in `check_validity!' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/associations/association.rb:25:in `initialize' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/associations/has_many_through_association.rb:9:in `initialize' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/associations.rb:157:in `new' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/associations.rb:157:in `association' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.0.0/lib/active_record/associations/builder/association.rb:70:in `collections' (irb):3 /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start' /users/jonathan/.rvm/gems/ruby-1.9.3-p392/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>' bin/rails:4:in `require' can tell me i've gotten wrong here. if doesn't see songs relationship collection? don't know i've done wrong.
as @damien pointed out in comment needed change:
has_many :collectionitems, through: :collectable to:
has_many :collectionitems, as: :collectable once in place everythign worked expected.
thanks again @damien!
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