As you know, assignable_values does not invalidate a record even when an attribute value becomes unassignable. See this example about songs:
class Song < ActiveRecord::Base
belongs_to :artist
belongs_to :record_label
assignable_values_for :artist do
record_label.artists
end
end
We'll create two record labels with one artist each and create a song for one artist. When we change the song's record label, its artist is still valid.
makandra = RecordLabel.create! name: 'makandra records'
dominik = Artist.create! name: 'dominik', record_label: makandra
apple = RecordLabel.create! name: 'apple music'
steve = Artist.create! name: 'steve', record_label: apple
song = Song.create! name: 'gem session', artist: dominik, record_label: makandra
song.assignable_artists = [dominik]
song.record_label = apple
song.assignable_artists = [steve, dominik] # dominik has legacy rights!
song.valid? # => true
When you are trying to find the intended assignable values for that song, dominik is unexpected because he is no artist of the apple record label.
Cure
assignable_values 0.11.0 introduces an option that does what you need:
song.assignable_artists(include_old_value: false) # => [steve]
This may be needed when updating a select field via AJAX, where it is not about validating but displaying valid choices.
Posted by Dominik Schöler to makandra dev (2014-06-10 15:06)