Equivalent of belongs_to through in rails model

Question

What I want to do is to get the equivalent of belongs_to through. My rationale is that I don't want to generate lots of db calls, while traversing my model structure.

My example in pseudo format:

Manufacturer
  has_many: machines

Factory
  has_many: machines
  has_many: people

Machine
  belongs_to: manufacturer
  belongs_to: factory

People
  belongs_to: factory

I want starting from a Manufacturer record(s), to get all the people in the factory where those manufacturers machines exist.

The only way I can think of is by iterating through manufacturer.machines.each, and calling factory.people (or calling people using a delegate), but I'd love to do it all in one call.

Is there a way?

Answer 1

In your Manufacturer model you could have these relations:

has_many :machines # You probably already have this one
has_many :factories, through: :machines
has_many :people, through: :factories

Let's say bob is a Manufacturer . You can now get all the people in all the factories where bob 's machines exist.

bob.people

Note that I renamed the People model to Person when I tested it. You should try to keep your model names singular as much as possible.