Rails关联中的未知密钥

我有以下协会代码：

has_many :rates_without_dimension, :as => :rateable, :class_name => "Rate", :dependent => :destroy, :conditions => {:dimension => nil} has_many :raters_without_dimension, :through => :rates_without_dimension, :source => :rater has_one :rate_average_without_dimension, :as => :cacheable, :class_name => "RatingCache", :dependent => :destroy, :conditions => {:dimension => nil} dimensions.each do |dimension| has_many "#{dimension}_rates", :dependent => :destroy, :conditions => {:dimension => dimension.to_s}, :class_name => "Rate", :as => :rateable has_many "#{dimension}_raters", :through => "#{dimension}_rates", :source => :rater has_one "#{dimension}_average", :as => :cacheable, :class_name => "RatingCache", :dependent => :destroy, :conditions => {:dimension => dimension.to_s} end 

它引发了一个错误：

 Unknown key: :conditions. Valid keys are: :class_name, :class, :foreign_key, :validate, :autosave, :table_name, :before_add, :after_add, :before_remove, :after_remove, :extend, :primary_key, :dependent, :as, :through, :source, :source_type, :inverse_of, :counter_cache 

我试图将第一行改为：

 has_many :rates_without_dimension, :as => :rateable, :class_name => "Rate", :dependent => :destroy,-> { where(:dimension => nil) } 

但它也引发了一个错误，你能指出我有什么问题吗？

Answer 1

这里描述了同样的问题https://teamtreehouse.com/forum/unknown-key-conditions

正如我在示例中看到的，带有条件的lambda应该在关联名称之后执行，因为没有{} hash只能作为最后一个参数。

尝试

 has_many :rates_without_dimension, -> { where(dimension: nil) }, as: :rateable, class_name: "Rate", dependent: :destroy 

ps你可以使用http://apidock.com/rails/Object/with_options使它看起来更好