ruby-on-rails - 无法从验证中调用关联方法

Question

我在验证中调用由我的关联生成的方法时遇到问题。

我的代码很简单:

class Match < ActiveRecord::Base
  # Associations
  belongs_to :tournament

  has_many :match_player_relations
  has_many :waiting_players, through: :match_player_relations
  has_many :replays

  # Validations
  validates :tournament_id, presence: true
  validates :winner_id, inclusion: { in: waiting_players.map { |wp| wp.id } }
end

我已经在我的测试中验证有一个 waiting_players 方法，并且它可以正常工作。但是，当我尝试在验证中调用它时，出现以下错误:

/Users/max/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.1.3/lib/active_record/base.rb:1088:in `method_missing': undefined local variable or method `waiting_players' for #<Class:0x007fc3b498c9c8> (NameError)
    from /Users/max/workplace/CloudLeagues/app/models/match.rb:11:in `<class:Match>'

有没有办法解决这个问题？还是我需要删除验证？

Answer 1

很确定您需要将 lambda 传递给 in访问当前记录:

validates :winner_id, inclusion: { 
  in: lambda {|match| match.waiting_players.map { |wp| wp.id }}
}