导轨 - 3个车型之间建立关系呢查询

Question

我想基本上建立关系如下：

组模式

has_and_belongs_to_many :users 
has_many :posts 

用户模型

has_and_belongs_to_many :groups 
has_many :posts 

邮政型号

belongs_to :group 
belongs_to :user 

当我查询用户的帖子时，我可以做user.posts。但是，我无法弄清楚如何查询用户加入的组中的所有帖子。任何建议表示赞赏！

Answer 1

你想

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

Answer 2

一些进一步阅读你：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