如何向依赖于另一个模型的 Rails 模型添加验证

Question

找不到轻松完成此任务的最佳方法 我想为以下问题提出数据库模型。

有一个 Deal 表，它有一个关联的 account 表。每个帐户可以有多个联系人。现在，一笔交易需要分配一个主要联系人，该联系人必须是关联帐户的众多联系人之一。如何确保主要联系人是帐户联系人之一。

Deal Table
  account_id
  primary_contact_id

Account Table
  name and other params

Contact Table
  account_id
  phone, email etc.

例如。我目前使用的类

class Deal < ActiveRecord::Base
  belongs_to :account
  belongs_to :contact
end

class Account < ActiveRecord::Base
  has_many :contacts
  has_many :deals
end

class Contact < ActiveRecord::Base
  belongs_to :account
  has_many :deals
end

我可以在交易模型或控制器中添加验证，以确保添加的联系人是其帐户联系人之一。但是如何处理以下情况：

1. 从账户中删除联系人应确保deal表对应的contact_id设置为nil
2. 删除与交易关联的帐户应确保该交易表的contact_id 无效
3. 更新帐户关联应确保交易的contact_id 无效。

Answer 1

也许你可以使用模型回调，例如：

class Deal < ActiveRecord::Base
  belongs_to :account
  belongs_to :contact

  before_update :nullify_contact_association, :if => lambda{|i| i.account_id_changed?}

  private
  # Nullify contact_id of the deal if it's account association was changed
  def nullify_contact_association
    self.contact_id = nil
  end
end

class Account < ActiveRecord::Base
  has_many :contacts
  has_many :deals

  before_destroy :nullify_dependencies

  private

  #Deleting an account associated with a deal should
  #make sure that contact_id of that deal table is nullified
  def nullify_dependencies
    self.deals.update_all(:contact_id => nil) if deal.present?
  end
end

class Contact < ActiveRecord::Base
  belongs_to :account
  has_many :deals

  before_destroy :nullify_dependencies

  private

  #Deleting a contact from an account should make sure
  #that corresponding contact_id of the deal table is set to nil
  def nullify_dependencies
    self.deals.update_all(:contact_id => nil) if account.present?
  end
end

Answer 2

class Deal

  validate :contact_is_among_the_contacts_in_associated_account

  private

  def contact_is_among_the_contacts_in_associated_account
    errors.add(:contact_id, "Your error message") unless contact.in?(account.contacts)
  end

end