Rails - Columns pointing to same table

Question

I have a database with tables containers and ports.

The containers table has two columns pol_id and pod_id that both point to the ports table. The ports table has an id column.

I have tried using belongs_to / references inside the migration but it does not provide such flexibility.

Also, I am a bit puzzled at configuring the models for this.

I think you juste want to specify the foreign_key in your belongs_to association. — Mathiou, Jul 01 '17 at 10:54
Here is a good answer for your model configuration : https://stackoverflow.com/questions/25047920/rails-belongs-to-with-custom-column-name — Mathiou, Jul 01 '17 at 11:01

score 0 · Answer 1 · answered Jul 01 '17 at 14:59

You can use the foreign_key option when creating the migration to customize the foreign key:

t.references(:pol, foreign_key: { to_table: :ports })

In your model you need to tell ActiveRecord what class the association points to:

class Container
  belongs_to :pol, class_name: "Port"
end

You also need to provide the foreign key when creating the inverse association:

class Port
   has_many :containers_as_pol, class_name: "Container", foreign_key: "pol_id"
end

Note that the belongs_to in migrations is just an alias for references so the same applies. — max, Jul 01 '17 at 15:01

1 Answers1