ruby-on-rails – Rails：验证foo的存在,除非bar ==’baz’

我正在研究一个模型,该模型在创建对象时需要设置两个关联,在一种情况下除外.

基本上,它需要像这样工作.

class Example < ActiveRecord::Base
  has_one :foo
  has_one :bar

  validates_presence_of :foo
  validates_presence_of :bar,:unless => :foo == Foo.find_by_name('ThisFoodoesntLikeBars')
end

我不确定如何构建：除非条件在这里,因为它需要检查：foo是否是特定对象.

你怎么做这样的事情？

解决方法

：除非接受Proc

validates_presence_of :bar,:unless => Proc.new { |ex| ex.foo == Foo.find_by_name('ThisFoodoesntLikeBars') }

:unless – Specifies a method,proc or string to call to determine if the validation should not occur (e.g. :unless => :skip_validation,or :unless => Proc.new { |user| user.signup_step <= 2 }). The method,proc or string should return or evaluate to a true or false value.

http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html