Rails的条件验证抛出未定义的方法型号

Question

所以，我一直工作在一个应用程序（Rails的5），我想确认是否由用户选择的属性（服务器）是我想要的范围。

class Player < ApplicationRecord 
    validates :nick, presence: true, length: { maximum: 20 } 
    validates :description, length: { maximum: 275 } 
    validates :server, presence: true, if: server_exists? 

    def server_exists? 
    server == "NA" 
    end 

end 

当我试图访问localhos：3000我得到以下错误：

undefined method `server_exists?' for Player (call 'Player.connection' to establish a connection):Class

有谁知道如何解决它？

谢谢！

Answer 1

You can associate the :if and :unless options with a symbol corresponding to the name of a method that will get called right before validation happens.

与:server_exists?尝试，而不是server_exists?：

validates :server, presence: true, if: :server_exists? 

Answer 2

您需要使用符号的方法名称：

http://guides.rubyonrails.org/active_record_validations.html#using-a-symbol-with-if-and-unless

validates :server, presence: true, if: :server_exists?