Ruby on rails 如何在Rails中替换内存中的模型关联？

假设我有一个人模型，一个人有很多宠物，一只宠物与狗和猫有多态性关联。请注意，一个人不能有他/她过敏的动物

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
  validate :not_allergic_to_animal

  def not_allergic_to_animal
    if allergic_to_cats? && owns_a_cat?
      errors.add(:pets, 'cannot have a cat if allergic to cats')
    elsif allergic_to_dogs? && owns_a_dog?
      errors.add(:pets, 'cannot have a dog if allergic to dogs')
    end
  end

  def owns_a_cat?
    pets.any? { |pet| pet.animal_type == Cat.name }
  end

  def owns_a_dog?
    pets.any? { |pet| pet.animal_type == Dog.name }
  end
end

class Pet < ActiveRecord::Base
  belongs_to :user
  belongs_to :animal, polymorphic: true

  validates :animal_type, inclusion: { in: [Cat.name, Dog.name] } 
end

class Cat < ActiveRecord::Base
end

class Dog < ActiveRecord::Base
end

鲍勃喜欢爱丽丝，但阿黛尔是一只非常好斗的猫，所以鲍勃不再想要它了。他还想要一只狗。因此，他决定向其端点执行PUT请求。3是狗杰克的身份证，1是猫爱丽丝的身份证

PUT /me/ {
  "pets": {
    "dog_ids": [3],
    "cat_ids": [1]
  }
}

现在问题来了

如何在内存中替换Bob的宠物，验证Bob以确保他对任何宠物都不过敏，然后保存关联（不使用数据库事务）

我知道可以使用

#build

在内存中创建关联，但我不想附加到现有关联，而是在保存之前替换现有关联，全部在内存中。因此，上面的示例将在验证Person实例后执行两个数据库查询，一个用于为Jack the dog创建宠物关联，另一个用于在验证后删除Adele the cat的关联

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
  validate :not_allergic_to_animal

  def not_allergic_to_animal
    if allergic_to_cats? && owns_a_cat?
      errors.add(:pets, 'cannot have a cat if allergic to cats')
    elsif allergic_to_dogs? && owns_a_dog?
      errors.add(:pets, 'cannot have a dog if allergic to dogs')
    end
  end
  def owns_a_cat?
    pets
      .reject(&:marked_for_destruction?)
      .any? { |pet| pet.animal_type == Cat.name }
  end

  def owns_a_dog?
    pets
      .reject(&:marked_for_destruction?)
      .any? { |pet| pet.animal_type == Dog.name }
  end
end


bob = Person.where(name: 'Bob')

alice = Cat.where(name: 'Alice')
bob.pets.create!(animal: alice)

adele = Cat.where(name: 'Adele')
bob.pets.create!(animal: adele)

jack = Dog.create

bob.pets.find_by(animal_type: Cat.name, animal_id: adele.id).mark_for_destruction

bob.pets.build(animal: jack)
bob.valid?
bob.save!

我试图操纵

ActiveRecord:：Associations:：CollectionProxy

，但在删除或添加元素时，它总是在数据库中提交

请注意，我不想创建一个param验证器，只想验证id，其他接口可以用来更新个人，并且验证需要在所有这些接口之间保持一致，并且接近模型

编辑

---

我尝试将

#build

与

#mark#u一起使用以进行销毁

，但是如果替换不起作用，保存后将重新创建现有关联。

您可以使用

pets=

方法直接分配集合。比如说,

# Find the first pet
p1 = bob.pets.find_by_animal_id(alice.id)

# Create the second pet, this won't save yet
jack = Dog.find(3)
p2 = Pet.new(animal: jack)

bob.pets = [p1, p2]

---

我刚刚提出了一个解决方案：

如果

动物id

不在提供的id中，则标记要销毁的宠物，构建不存在的动物，并跳过验证中标记要销毁的动物

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
  validate :not_allergic_to_animal

  def not_allergic_to_animal
    if allergic_to_cats? && owns_a_cat?
      errors.add(:pets, 'cannot have a cat if allergic to cats')
    elsif allergic_to_dogs? && owns_a_dog?
      errors.add(:pets, 'cannot have a dog if allergic to dogs')
    end
  end
  def owns_a_cat?
    pets
      .reject(&:marked_for_destruction?)
      .any? { |pet| pet.animal_type == Cat.name }
  end

  def owns_a_dog?
    pets
      .reject(&:marked_for_destruction?)
      .any? { |pet| pet.animal_type == Dog.name }
  end
end


bob = Person.where(name: 'Bob')

alice = Cat.where(name: 'Alice')
bob.pets.create!(animal: alice)

adele = Cat.where(name: 'Adele')
bob.pets.create!(animal: adele)

jack = Dog.create

bob.pets.find_by(animal_type: Cat.name, animal_id: adele.id).mark_for_destruction

bob.pets.build(animal: jack)
bob.valid?
bob.save!

class-Person

执行

bob.pets=[p1，p2]

将在数据库中保存宠物关联。我想在执行任何数据库事务之前，将pets分配给内存中的bob以验证bob。理论上这显然是可能的，但ActiveRecord不允许我这么做。