嵌套記錄驗證：需要驗證小孩和父母一起

Question

Account < AR 
    has_many :deposits 
    accepts_nested_attributes_for :deposits 
    attr_accessible :max_amount 
end 

Deposit < AR 
    belongs_to :account 
    attr_accessible :amount 

    validate :validates_amount_less_than_max_amount 

    def validates_amount_less_than_max_amount 
    # How do you write this method? When an Account is being created with a nested 
    # Deposit, it should do this validation, but account is nil until 
    # saved, so @contribution can't access the :max_amount and validate from it. 
    # Solution? 
    end 
end 

Answer 1

這裏的答案：

https://rails.lighthouseapp.com/projects/8994/tickets/2815-nested-models-build-should-directly-assign-the-parent

補丁定於2.3.5。如果您現在需要該功能，則必須應用它及其依賴項。

Answer 2

使用此驗證，符合市場預期：

def validates_amount_less_than_max_amount 
    errors.add(:amount, 'is more than max amount') if self.amount > account.max_amount 
end 

但你不能用new建立在同一時間的賬戶及存款，因爲你在上面指出。嘗試在交易中創建帳戶/存款：

>> Account.transaction do 
>> a = Account.create!({:max_amount => 1000}) 
>> a.deposits_attributes = [{:amount => 1500}] 
>> a.save! 
>> end 
ActiveRecord::RecordInvalid: Validation failed: Deposits amount is more than max amount 

有關更多示例，請參見what's new in edge rails 2.3。