嵌套记录验证：需要验证小孩和父母一起

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

这里的答案：

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

补丁定于2.3.5。如果您现在需要该功能，则必须应用它及其依赖项。

Answer 2

使用此验证，符合市场预期：

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建立在同一时间的账户及存款，因为你在上面指出。尝试在交易中创建帐户/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 

有关更多示例，请参见what's new in edge rails 2.3。