模型协会属于并拥有答案

【问题标题】：Models associations belongs to and has模型协会属于并拥有
【发布时间】：2014-02-06 19:38:19
【问题描述】：

对于以下应该如何模型关联

User can purchase many Items
Items can be purchased by many users
Items have many categories

【问题讨论】：

标签： ruby-on-rails ruby-on-rails-3 activerecord model associations

【解决方案1】：

Active Record Associations 文档似乎不言自明！

您需要User 和Item 之间的has_many...through 关系，以及Item 和Category 之间的has_many 关系。

# app/models/user.rb
class User < ActiveRecord::Base
  has_many :purchases
  has_many :items, through: :purchases
end

# app/models/item.rb
class Item < ActiveRecord::Base
  has_many :purchases
  has_many :users, through: :purchases
  has_many :categories
end

# app/models/purchase.rb
class Purchase < ActiveRecord::Base
  belongs_to :user
  belongs_to :item
end

# app/models/category.rb
class Category < ActiveRecord::Base
  belongs_to :item
end

【讨论】：