multiple belongs_to has_one

multiple_belongs_to.rb

Trip >
  belongs_to :origin, class_name: 'City'
  belongs_to :destiny, class_name: 'City'

City >
  has_many :origins, class_name: 'Trip', foreign_key: 'origin_id'
  has_many :destinys, class_name: 'Trip', foreign_key: 'destiny_id'

Migration >

class AddOriginAndDestinyToTrip < ActiveRecord::Migration[5.0]
  def change
    add_reference :trips, :origin, foreign_key: {to_table: :cities}
    add_reference :trips, :destiny, foreign_key: {to_table: :cities}
  end
end