sql - Rails - 一个模型上的两个外键都指向同一个模型

Question

我对 ActiveRecord 关联很陌生。我正在草拟一个应用程序，用于跟踪一组用户之间谁欠彼此的钱。安 Expense模型和 User模型似乎是自然的选择，我只是不确定如何定义两者之间的关系。例如，我想跟踪每笔费用的债权人(“所有者”)和债务人，但这实际上只是返回给 User 的两个外键。此外，每个用户可以有多项费用(作为债权人和债务人)到目前为止我对协会的最佳猜测是这样的:

class Expense
    # belongs_to or has_one here?
    # Not sure about class => User syntax:
    # need to alias to foreign keys that reference the same model
    belongs_to :creditor, :class => User 
    belongs_to :debtor, :class => User

class User
    # has_many expenses defines a creditor relationship (user owns expense)
    # how to define debtor relationship? (belongs_to...?)
    has_and_belongs_to_many :expenses

我已经阅读了关于关联的 Rails 指南，但我仍然对外键和连接表迷失了方向。非常感谢任何输入!

Answer 1

所以这绝对不是 has_and_belongs_to_many那是多对多关系。你只需要使用一对 has_many关系。我认为它最终应该是这样的:

编辑:哎呀，我捏造了一点，对不起，让我再试一次:

class Expense
  # make sure expense table has 'creditor_id' and 'debtor_id' rows
  belongs_to :creditor, :class_name => "User", :foreign_key => :creditor_id
  belongs_to :debtor, :class_name => "User", :foreign_key => :debtor_id

class User
  has_many :debts, :class_name => "Expense", :foreign_key => :debtor_id
  has_many :credits, :class_name => "Expense", :foreign_key => :creditor_id