accepts_nested_attributes_for在验证外键时出现问题

Question

我使用的是Ruby on Rails V3.2.2。我想解决在使用accepts_nested_attributes_for和validates_associatedRoR方法时与外键验证相关的问题。也就是说，我有以下模型类：

class Article < ActiveRecord::Base
  has_many :category_associations, :foreign_key => 'category_id'

  accepts_nested_attributes_for :category_associations, :reject_if => lambda { |attributes| attributes[:category_id].blank? }
  validates_associated :category_associations
end

class CategoryAssociation < ActiveRecord::Base
  belongs_to :article, :foreign_key => 'article_id'
  belongs_to :category, :foreign_key => 'category_id'

  validates :article_id, :presence => true
  validates :category_id, :presence => true
end

class ArticlesController < ApplicationController
  def new
    @article = Article.new
    5.times { @article.category_associations.build }

    # ...
  end

 def create
   @article = Article.new(params[:article])

   if @article.save
     # ...
   else
     # ...
   end
 end
end

{:"category_associations.article_id"=>["can't be blank"], :category_associations=>["is invalid"]}

但是，如果我注释掉categoryAssociation模型类中的validates:article_id,:presence=>true，它会按预期工作，但是不验证外键似乎不是一个正确的方法。

如果我注释掉文章模型类中的validates_Associated:category_Associations，我仍然会得到错误：

{:"category_associations.article_id"=>["can't be blank"]}

Answer 1

使用INVERSE_OF链接关联，然后验证关联对象的存在，而不是实际外键的存在。

文档中的示例：

class Member < ActiveRecord::Base
  has_many :posts, inverse_of: :member
  accepts_nested_attributes_for :posts
end

class Post < ActiveRecord::Base
  belongs_to :member, inverse_of: :posts
  validates_presence_of :member
end