validates_presence_of這些關聯中的至少一個

Question

A WithdrawalAccount記錄包含SepaAccount,InternationalAccount,PayPalAccount或OtherAccount。至少應該是其中之一。不能超過一個。

class WithdrawalAccount < ActiveRecord::Base 
    has_one :sepa_account 
    has_one :international_account 
    has_one :third_account 
    has_one :fourth_account 
end 

更新問題： 我如何validate_presence_of它們中的一個，而只允許其中的一個存在。

Answer 1

嘗試：

class WithdrawalAccount < ActiveRecord::Base 
    has_one :sepa_account 
    has_one :international_account 

    validates :sepa_account,   presence: true, if: ->(instance) { instance.international_account.blank? } 
    validates :international_account, presence: true, if: ->(instance) { instance.sepa_account.blank? } 
end 

要驗證任何一個，你應該更喜歡下面的方法：

class WithdrawalAccount < ActiveRecord::Base 

    validate :accounts_consistency 

    private 

    def accounts_consistency 
    # XOR operator more information here http://en.wikipedia.org/wiki/Xor 
    unless sepa_account.blank?^international_account.blank? 
     errors.add(:base, "options consistency error") 
    end 
    end 
end 

擁有超過2個屬性來驗證：

由於XOR將不工作與超過2個屬性（a^b^c）我們可以ch埃克使用循環屬性：

def accounts_consistency 
    attributes = [sepa_account, international_account, third_account, fourth_account] 
    result = attributes.select do |attr| 
    !attr.nil? 
    end 

    unless result.count == 1 
    errors.add(:base, "options consistency error") 
    end 
end 

Answer 2

你可以這樣做

validate :account_validation 

private 

def account_validation 
    if !(sepa_account.blank?^international_account.blank?) 
    errors.add_to_base("Specify an Account") 
    end 
end 

有答案這裏（Validate presence of one field or another (XOR)）