Mongoid、belongs_to和embedded_in hot id可以做什么？

【问题标题】：Mongoid, belongs_to and embedded_in hot can id do?Mongoid、belongs_to和embedded_in hot id可以做什么？
【发布时间】：2012-09-07 13:47:14
【问题描述】：

我有三个模型：用户、图片和点赞

地点：

class Picture
    include Mongoid::Document
    embeds_many :likes
    belongs_to :user
end
class User
    include Mongoid::Document
    has_many :pictures
    has_many :likes
end
class Like
    include Mongoid::Document
    belongs_to :user
    embedded_in :picture
end

不，我想将喜欢的内容存储到那时：

查看有多少赞有一张图片 (Picture.first.likes.count)
查看用户有多少赞 (User.first.likes.count)
查看用户点赞的图片是什么？

这个 Schema 是否正确地实现了这三个要求？

【问题讨论】：

标签： ruby-on-rails mongoid ruby-on-rails-3.2

【解决方案1】：

第一件事，嵌入模型不能在其他用户中引用，就像您尝试在用户中引用 Like（已嵌入图片中）一样。

正确的模型结构将是

class Picture
    include Mongoid::Document
    has_and_belongs_to_many :likers, :class_name => "User", :inverse_of => nil
    belongs_to :user
end

class User
    include Mongoid::Document
    has_many :pictures
end

现在回答您的疑问

# See how many likes have a picture
Picture.first.likers.count
# See how many likes a user has
# (assumption - will have only one like from one user for a specific picture)
Picture.where(:liker_ids => User.first).count
# See to what picture the user make a like?
Picture.where(:liker_ids => User.first).all

【讨论】：