的has_many通过，有条件

Question

我有一个标签型号：

name:string 
user_tag: boolean 
private_tag: boolean 

，并用一个简单的连接表的图像模型（picture_id，TAG_ID）

我想有picture.tags，picture.user_tags ，和picture.private_tags为什么下面的代码不工作，我应该如何解决它？

has_many :tags, -> { where :private_tag => false and :user_tag => false }, through: :pictures_tags 
has_many :private_tags, -> { where :private_tag => true }, through: :pictures_tags 
has_many :user_tags, -> { where :user_tag => true }, through: :pictures_tags 

!!编辑！

所以我得到了它不能在这里工作：

has_many :tags, through: :pictures_tags, :source => :tag, :conditions => ['tags.private_tag = ? and tags.user_tag = ?', false, false] 
has_many :private_tags, through: :pictures_tags, :source => :tag, :conditions => ['tags.private_tag = ?', true] 
has_many :user_tags, through: :pictures_tags, :source => :tag, :conditions => ['tags.user_tag = ?', true] 

但它似乎是回到了两次。

2.1.1 :036 > picture = Picture.last 
Picture Load (0.4ms) SELECT "pictures".* FROM "pictures" ORDER BY "pictures"."id" DESC LIMIT 1 
=> #<Picture id: 378, user_id: 35, picture: "i6.JPG", created_at: "2014-11-23 12:19:35", 
updated_at:"2014-11-23 12:19:35", number_of_votes: 0, number_of_upvotes: 0, 
blurb: "!test @test #test"> 
2.1.1 :037 > picture.private_tags 
Tag Load (0.2ms) SELECT "tags".* FROM "tags" INNER JOIN "pictures_tags" ON "tags"."id" = "pictures_tags"."tag_id" WHERE (tags.private_tag = 't') AND "pictures_tags"."picture_id" = ? [["picture_id", 378]] 
=> #<ActiveRecord::Associations::CollectionProxy 
[#<Tag id: 198, name: "!test", created_at: "2014-11-23 12:19:35", updated_at: "2014-11-23 12:19:35", 
private_tag: true, user_tag: false>, #<Tag id: 198, name: "!test", created_at: "2014-11-23 12:19:35", 
updated_at: "2014-11-23 12:19:35", private_tag: true, user_tag: false>]> 
2.1.1 :038 > picture.private_tags.count 
(0.3ms) SELECT COUNT(*) FROM "tags" INNER JOIN "pictures_tags" ON "tags"."id" = "pictures_tags"."tag_id" WHERE (tags.private_tag = 't') AND "pictures_tags"."picture_id" = ? [["picture_id", 378]] 
=> 2 

Answer 1

您可能遇到语法问题。这些协会：

has_many :private_tags, -> { where :private_tag => true }, through: :pictures_tags 
has_many :user_tags, -> { where :user_tag => true }, through: :pictures_tags 

都很好。问题是：

has_many :tags, -> { where :private_tag => false and :user_tag => false }, through: :pictures_tags 

因为where条款并不需要一个条件作为参数（它不是一个有效的条件要么），但Hash。所以它会是：

has_many :tags, -> { where :private_tag => false, :user_tag => false }, through: :pictures_tags