在多态表中获取 STI 类型

Question

我有很多类型的车辆，都有各自的品牌。 每辆车都有一个品牌。在下面的这种情况下，我试图弄清楚如何让 .brandable_type 等于 .type

如何返回 Vehicle::Car 类型的 base_class？

控制台：

vehicle = Vehicle.create(name: 'Mustang GT', type: 'Vehicle::Car')
vehicle.create_brand!(name: 'Ford')

Vehicle.find_by(name: 'Mustang GT').brand       #returns brand
Brand.find_by(name: 'Ford').brandable_type      #returns 'Vehicle' not 'Vehicle::Car'

迁移：

class CreateVehicles < ActiveRecord::Migration
  def change
    create_table :vehicles do |t|
      t.string :name
      t.string :type

      t.timestamps
    end

    add_index :vehicles, [:id, :type]
  end
end


class CreateBrands < ActiveRecord::Migration
  def change
    create_table :brands do |t|
      t.integer :brandable_id
      t.string :brandable_type

      t.string :name

      t.timestamps
    end

    add_index :brands, [:brandable_id, :brandable_type]
  end
end

型号：

# app/models/vehicle.rb
class Vehicle < ActiveRecord::Base 
  has_one :brand, class_name: Brand, as: :brandable
end

# app/models/vehicle/car.rb
class Vehicle::Car < Vehicle
end

# app/models/vehicle/bicycle.rb
class Vehicle::Bicycle < Vehicle
end

# app/models/brand.rb
class Brand
  belongs_to :brandable, polymorphic: true 

  def brandable_type=(sType)
    super(sType.to_s.classify.constantize.base_class.to_s)
  end
end

Answer 1

您省略了通过:brandable 将车辆与品牌相关联：

class Vehicle < ActiveRecord::Base 
  has_one :brand, as: :brandable
end

另外我认为你的关联是不对的，除非你有特定的理由这样设置，因为 Brand 和 Vehicle 听起来应该是一对多的关系，Brand 更有可能拥有的车辆多于品牌属于具有一对一关联的车辆