Giving an association a custom name

06 May 2019

Sometimes, it may be desirable to reference an association with a name that differs from the one generated from the table name.

I have a model named Steps. Each step can have many steps. Each step belongs to one other parent step.

class Step < ApplicationRecord
  belongs_to :step
  has_many :steps
end

a = Step.create
b = Step.create
c = Step.create

a.steps >> b
a.steps >> c

I could get the parent step of b like so:

b.step
# => #<Step:0x00007fdf24b916e8

I don’t think that’s intuitive enough though. Since I’m asking for the parent step, it should be more like:

b.parent
# => #<Step:0x00007fdf24b916e8

Setting up the custom name is simple. I can supply the name of my choosing. Then, all I need to do is specify the class name and foreign id in the options.

class Step < ApplicationRecord
  belongs_to :parent, class_name: 'Step', foreign_key: :step_id
  has_many :steps
end