Question

我有这种愤怒的联想：融资＆gt; - 事件＆gt; - 子程序＆gt; - 程序。我希望通过所有程序从程序中访问last_financings，因此代码是：

class Fcp < Program
  has_many :fcp_subprograms,
           :foreign_key => 'parent_id'
  has_many :subprogram_last_actual_financings,
           :through => :fcp_subprograms,
           :source => :last_actual_financings

class FcpSubprogram < Program
  belongs_to :fcp,
             :class_name => 'Fcp',
             :foreign_key => 'parent_id'

  has_many :events,
           :foreign_key => 'fcp_id'

  has_many :last_actual_financings,
           :through => :events,
           :source => :last_actual_financings

class Event < ActiveRecord::Base
  belongs_to :fcp,
             :class_name => 'Fcp',
             :foreign_key => 'fcp_id'
  belongs_to :fcp_subprogram,
             :class_name => 'FcpSubprogram',
             :foreign_key => 'fcp_id'

  has_many :last_actual_financings,
           :class_name => 'ActualFinancing',
           :order => 'date DESC',
           :limit => 1

所以，当我想在after_initialize函数中访问subprogram_last_actual_financings时，我收到此错误

Invalid source reflection macro :has_many :through for has_many :subprogram_last_actual_financings, :through => :fcp_subprograms.  Use :source to specify the source reflection.

但我有：我的关联中的源选项。我做错了什么？

Answer 1

你得到的错误是关于source_reflection是一个无效的关联，因为has_many的源必须是belongs_to，has_one或has_many而没有through选项。所以你不能使用：last_actual_financings作为源。

Answer 2

据我记得你不能与双重（或更多）联系：通过。你唯一能做的就是编写自己的SQL查询。

以下是我的示例：

class Person
  ...
  has_many :teams, :finder_sql =>
    'SELECT DISTINCT teams.* FROM teams
        INNER JOIN team_roles ON teams.id = team_roles.team_id
        INNER JOIN team_members ON team_roles.id = team_members.role_id
        WHERE ((team_members.person_id = #{id}))'

  # other standard associations
  has_many :team_members
  has_many :team_roles,
    :through => :team_members
  # and I couldn't do:
  # has_many :teams, :through => :team_roles

这是关系人物 - ＆gt; has_many - ＆gt; team_members - ＆gt; has_many - ＆gt; team_roles - ＆gt; has_one - team。

希望它有所帮助。

Answer 3

这似乎是一种非常尴尬的做法...我宁愿在Program中创建一个虚拟访问器来调用这样的东西：

self.subprograms.first.events.first.financings.first(:order => 'date DESC')

源反射宏无效：has_many：through

3 个答案: