create_table :accessories do |t|
      t.references :good,              index: true, foreign_key: true
      t.references :good,              index: true, foreign_key: true

      t.timestamps
    end

create_table :accessories do |t|
      t.integer :good_id,                   index: true, foreign_key: true
      t.integer :accessory_id,              index: true, foreign_key: true

      t.timestamps

class Accessory < ApplicationRecord
  belongs_to :good, :class_name => 'Good'
  belongs_to :accessory, :class_name => 'Good'
end

class Good < ApplicationRecord
  has_many :active_relationships  , class_name: 'Accessory', foreign_key: 'accessory_id', dependent: :destroy
  has_many :passive_relationships , class_name: 'Accessory', foreign_key: 'good_id', dependent: :destroy

  has_many :main, through: :active_relationships    , source: :good
  has_many :depend, through: :passive_relationships , source: :accessory
end