如何在Rails验证中使用if语句？

Question

我正在尝试创建一个验证语句，如果存在service_area，则验证对象除service_area_radius==0

这是我创建的语句，它不起作用：

validates :service_area, :presence => true, unless: "service_area_radius==0"

Answer 1

http://railscasts.com/episodes/41-conditional-validations

像这样：

validates_presence_of :password, :if => :should_validate_password?
validates_presence_of :country
validates_presence_of :state, :if => :in_us?
attr_accessor :updating_password

def in_us?
  country == 'US'
end

def should_validate_password?
  updating_password || new_record?
end

Answer 2

validates :service_area,
     presence:  {message: "Area Radius is missing."}, if: :radius_found?

private 
 def radius_found? 
    service_area_radius > 0
 end

1. 如果radius_found，将执行service_area的验证？返回true。

2. radius_found？当service_area_radius（属性）保持值＆gt;时将返回true 0

3. 当验证失败时，使用message：选项添加自定义消息。