postgresql - 通过不同的名称关联同一个模型两次

Question

我正在尝试实现失物招领处数据库。我有两个型号，User和 Item .用户可以丢失一个项目并找到一个项目。一个项目可以有找到它的用户和丢失它的用户。我希望能够通过不同的名称引用相同的模型，例如

user.found_items, user.lost_items, item.founder, item.losser

现在我能做到:

user.founds , user.losts和 user.items将返回 items从丢失

class User < ActiveRecord::Base
  has_many :founds
  has_many :items, through: :founds

  has_many :losts
  has_many :items, through: :losts
end

class Lost < ActiveRecord::Base
  belongs_to :user
  belongs_to :item
end

class Found < ActiveRecord::Base
  belongs_to :user
  belongs_to :item
end

class Item < ActiveRecord::Base
  has_one :found
  has_one :user, through: :found

  has_one :lost
  has_one :user, through: :lost
end

Answer 1

我会做一些非常相似的事情，只是为了清楚起见重命名它们并为您想要的功能添加一些方法。

class User < ActiveRecord::Base

  has_many :found_items
  has_many :items, through: :found_item

  has_many :lost_items
  has_many :items, through: :lost_item

  def items_found
    self.found_items.map {|i| i.item.name }
  end

  def items_lost
    self.lost_items.map {|i| i.item.name }
  end

end

class LostItem < ActiveRecord::Base
  belongs_to :user
  belongs_to :item
end

class FoundItem < ActiveRecord::Base
  belongs_to :user
  belongs_to :item
end

class Item < ActiveRecord::Base
  has_one :found_item
  has_one :user, through: :found_item

  has_one :lost_item
  has_one :user, through: :lost_item

  def finder
    self.found_item.user.name
  end

  def loser
    self.lost_item.user.name
  end
end