I have 3 Models: Course, Unit and Plan. relations are like:
Course has_many units
Unit belongs_to course
Plan has_and_belongs_to_many units
Unit has_and_belongs_to_many plans
In the create_plan page, I have a collection_select to get units of my plan; but units don't have title,they use their course title. I want to show the course title in the collection_select. how can I do that?