Question

我有一个图节点类的实现，我希望它具有作为有向非循环图的功能。

协会大致如下

class Node
  has_many :edges

  has_many :parents,
           :foreign_key => 'parent_id',
           :through => :edge

  has_many :parent_edges,
           :foreign_key => 'child_id',
           :class_name => 'Edge',
           :dependent => :destroy

  # similar for children
end

class Edge
  belongs_to :parent,
             :class_name => 'Node'

  # similar for child

  has_many :edge_properties
end

当我尝试获取父节点的关系时，生成的查询仍然使用 node_id作为主键。

SELECT `nodes`.* 
FROM   `nodes` 
       INNER JOIN `edges` 
               ON `nodes`.`id` = 
                  `edges`.`parent_id` 
WHERE  `edges`.`node_id` = 16             # where clause uses node_id, should be child_id
ORDER  BY `nodes`.`name` ASC

如何更改该查询以在where子句中使用child_id？

Answer 1

正确的解决方案（也是TIL：通过选项可以指定另一个关联）

 has_many :parent_edges,
          :foreign_key => 'child_id',
          :class_name => 'Edge',
          :dependent => :destroy

 has_many :parents,
          :source => 'parent',
          :through => :parent_edges  # using another association

如何在直通关联中指定主键

1 个答案: