ruby-on-rails - Rails - 建立3个模型之间的关系并进行查询

Question

我试图建立一种基本上如下的关系：

组模型

has_and_belongs_to_many :users
has_many :posts

用户模型

has_and_belongs_to_many :groups
has_many :posts

后模型

belongs_to :group
belongs_to :user

当我查询用户的帖子时，我可以做 user.posts。但是，我不知道如何从用户加入的组中查询所有帖子。任何建议表示赞赏！

Answer 1

你要

class User < ActiveRecord::Base
  has_and_belongs_to_many :groups
  has_many :posts
  has_many :group_posts, through: :groups, source: :posts
end

Answer 2

一些进一步的阅读：has_many :through

class Physician < ActiveRecord::Base
  has_many :appointments
  has_many :patients, through: :appointments
end

class Appointment < ActiveRecord::Base
  belongs_to :physician
  belongs_to :patient
end

class Patient < ActiveRecord::Base
  has_many :appointments
  has_many :physicians, through: :appointments
end