Well that's kind of what I need help with, I'm not sure where it needs to be defined in a many-to-many relationship. I've already created the join table that contains both ids.
The point is that your example makes no sense; you've defined this as a "to-many" relationship -- which Model_1 are you looking for?
Hassan Schroeder wrote in post #1074840:
But you're not showing us a view, you're showing us a model.
Do you really want `some_method` to return one value or an array of values?
If you only want one value, why don't you pass the Model_1 instance (or the attribute) you're interested in to the Model_2 instance?
def some_method(model_1_attribute) attr_a * model_1_attribute end