Is there a way in rails to make a model optionally belong to another model?

Question

I am building a rails exercise app that has both exercises and routines. I want each routine to be composed of several exercises (has_many :exercises), but an exercise doesn't necessarily have to belong to a routine. Is there a way to do that?

Answer 1

Reading the guides is always a good start. This works from Rails 5 onwards.

belongs_to :routine, optional: true