ActiveRecord question

gistfile1.md

AR association with special attributes

Is there a straightforward way to have an intermediate model in AR (has many through type of scenario) which adds attributes to the association?

E.g.: has_many :fruits, :through => :qualified_fruits, :class_name => 'Fruit'.

Fruit objects returned have a "quality" attribute which actually lives in :qualified_fruits.

Yep - just have a through model that has other attributes ... accept nested on parent to populate through model

Not automatically, and my experience with AR tells me that trying to trick it into doing it automatically will just cause you pain.

The closest I can think of is this pattern:

has_many :fruits, class_name: QualifiedFruit

class QualifiedFruit < ActiveRecord::Base
  belongs_to :fruit

  delegate :taste, :colour, :ripeness, to: :fruit
end

something like:

class MachineMembership < ActiveRecord::Base
  belongs_to :machine
  belongs_to :user

  as_enum :role, user: 0, admin: 1, owner: 3
end

class Machine < ActiveRecord::Base
  has_many :machine_memberships, dependent: :destroy
end

class User < ActiveRecord::Base
  has_many :machine_memberships, dependent: :destroy
end

@machine = Machine.new(machine_params)
@machine.machine_memberships.build({role: :owner, user: current_user})
if @machine.save

The migration for join table :

class CreateMachineMemberships < ActiveRecord::Migration
  def change
    create_table :machine_memberships do |t|
      t.integer :role_cd, null: false
      t.belongs_to :machine
      t.belongs_to :user

      t.timestamps
    end

    add_index :machine_memberships, [:machine_id, :user_id], unique: true, name: 'index_machine_memberships_unique'
  end
end

Quick copy/paste left off one line lol

class Machine < ActiveRecord::Base
  has_many :machine_memberships, dependent: :destroy
  has_many :users, through: :machine_memberships
end

That gives you

machine.users