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我已經創建了一個啓發我的問題的示例應用程序。has_many:通過關聯反向添加兩次
基本上,我有一個STI類許多一對多關聯關係:
class Basket < ActiveRecord::Base
has_many :basket_fruits, inverse_of: :basket
has_many :fruits, through: :basket_fruits
has_many :apples, through: :basket_fruits, source: :fruit, class_name: 'Apple'
has_many :oranges, through: :basket_fruits, source: :fruit, class_name: 'Orange'
has_many :bananas, through: :basket_fruits, source: :fruit, class_name: 'Banana'
end
class BasketFruit < ActiveRecord::Base
belongs_to :basket, inverse_of: :basket_fruits
belongs_to :fruit, inverse_of: :basket_fruits
validates :basket, :fruit, presence: true
end
class Fruit < ActiveRecord::Base
has_many :basket_fruits, inverse_of: :fruit
has_many :baskets, through: :basket_fruits
validates :type, presence: true, inclusion: ['Apple', 'Banana', 'Orange']
validates :baskets, presence: true
end
class Apple < Fruit; end
class Banana < Fruit; end
class Orange < Fruit; end
模式:
Basket(id: integer, created_at: datetime, updated_at: date time)
BasketFruit(id: integer, fruit_id: integer, basket_id: integer, created_at: datetime, updated_at: date time)
Fruit(id: integer, type: string, created_at: datetime, updated_at: datetime)
當使用ActiveAdmin創建一個新的香蕉,它使用的代碼,這相當於到:
Basket.create
banana = Basket.first.bananas.build(basket_ids: [Basket.first.id])
發生的問題是,此代碼創建兩個關聯,其中ca n即使不保存香蕉也可以觀察到:
banana.basket_fruits.size
=> 2
爲什麼會發生這種情況,以及如何解決它?
更新
剛剛發現這一點。也許這就是爲什麼AR正試圖增加兩倍的關係,而不是「壓倒一切」,因爲我本來期望:
banana = Basket.first.bananas.build
=> #<Banana id: nil, type: "Banana", created_at: nil, updated_at: nil>
banana.baskets
=> #<ActiveRecord::Associations::CollectionProxy []>
在這種情況下,一個需要填補了電話後,聯想前到#build
驗證阻止我這樣做。 – ybart