两个belongs_to的关联同型号 [英] Same Model for Two belongs_to Associations

问题描述

我有一个模型 PointOfContact 其中的has_many 系统 。从系统身边，我想确定 PointOfContact 为任 technical_manager 或 project_manager （或两者）。虽然仍只保留 PointOfContact 1时在数据库中。

我尝试如下：

 类System＆LT; ActiveRecord的::基地
  belongs_to的：project_manager，：CLASS_NAME =＆GT; '接触点'
  belongs_to的：technical_manager，：CLASS_NAME =＆GT; '接触点'
结束类PointOfContact＆LT; ActiveRecord的::基地
  的has_many：系统
结束
 

当我跑我的规格（例如下面），我可以正确地创建系统联络点关联性。但是， PointOfContact 不知道它与系统的关联。这是为什么？

  @sys = System.create
@tm = PointOfContact.create
@pm = PointOfContact.create@ sys.project_manager = @pm
@ sys.technical_manager = @tm@ pm.systems.should有（1）.items＃＆GT;预计1项，得到0
 

解决方案

由于在RailsForum.com jamesw过来：<一href=\"http://railsforum.com/viewtopic.php?id=43311%22Same%20Model%20for%20Two%20belongs_to%20Associations%22\">Same两个belongs_to的关联一个解决方案模型已经找到。

 类System＆LT; ActiveRecord的::基地
  belongs_to的：project_manager，：CLASS_NAME =＆GT; PointOfContact'，：foreign_key =＆GT; project_manager_id
  belongs_to的：technical_manager，：CLASS_NAME =＆GT; PointOfContact'，：foreign_key =＆GT; technical_manager_id
结束类PointOfContact＆LT; ActiveRecord的::基地
  的has_many：project_managed_systems，：CLASS_NAME =＆GT; 系统，：foreign_key =＆GT; project_manager_id
  的has_many：technical_managed_systems，：CLASS_NAME =＆GT; 系统，：foreign_key =＆GT; technical_manager_id
结束
 

I have an model PointOfContact which has_many Systems. From the Systems side I want to identify the PointOfContact as either the technical_manager or project_manager (or both). While still only keeping the PointOfContact 1 time in the DB.

My attempt follows:

class System < ActiveRecord::Base
  belongs_to :project_manager, :class_name => 'PointOfContact'
  belongs_to :technical_manager, :class_name => 'PointOfContact'
end

class PointOfContact < ActiveRecord::Base
  has_many :systems
end

When I run my specs (example follows) I can correctly create the System point of contact associations. However, the PointOfContact is not aware of its association with System. Why is that?

@sys = System.create
@tm = PointOfContact.create
@pm = PointOfContact.create

@sys.project_manager = @pm
@sys.technical_manager = @tm

@pm.systems.should have(1).items #> expected 1 items, got 0

解决方案

Thanks to jamesw over at RailsForum.com: Same Model for Two belongs_to Associations a solution has been found.

class System < ActiveRecord::Base
  belongs_to :project_manager, :class_name => 'PointOfContact', :foreign_key => 'project_manager_id'
  belongs_to :technical_manager, :class_name => 'PointOfContact', :foreign_key => 'technical_manager_id'
end

class PointOfContact < ActiveRecord::Base
  has_many :project_managed_systems, :class_name => 'System', :foreign_key => 'project_manager_id'
  has_many :technical_managed_systems, :class_name => 'System', :foreign_key => 'technical_manager_id'
end

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