无效源反射的宏：的has_many：通过

Question

我有这样的愤怒协会：融资> - 事件> - 子程序> - 程序。我想通过他们都获得查看在程序last_financings这样的代码是：

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，当我想访问subprogram_last_actual_financings在after_initialize功能我得到这个错误

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：在我协会源选项。我在做什么错了？

Answer 1

你得到的错误是关于source_reflection是无效的关联，因为来源的has_many通过必须是belongs_to的，HAS_ONE或无的has_many通过选项。所以你不能使用：last_actual_financings作为源

Answer 2

据我记得你不能让双（或更多）关联关系：通过。你能做的唯一的事情就是写自己的SQL查询。

下面是我的例子，如何做到这一点：

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 - >的has_many - > team_members - >的has_many - > team_roles - > HAS_ONE - 队

希望它能帮助。

Answer 3

这似乎是这样做的真正尴尬的方式......我宁愿做在Program虚拟访问调用是这样的：

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