具有多态关联的多个内连接

Question

我有以下多态关联...

class Activity < ActiveRecord::Base
  belongs_to :owner, polymorphic: true
end

class User < ActiveRecord::Base
  has_many :activities, as: :owner
end

class Manager < ActiveRecord::Base
  has_many :activities, as: :owner
end    

我试图进行一个查询,它只会拉出所有者(用户或经理)visible设置的活动true.

我已经想通了,如果我想为其中一位业主做这件事,我可以按照以下方式做到这一点......

Activity.joins("INNER JOIN users ON activities.owner_id = users.id").where(:activities => {:owner_type => 'User'}).where(:users => {:visible => true})

但我无法弄清楚如何为两者做到这一点.有人可以帮忙吗？

Answer 1

这应该工作:

Activity.
  joins("LEFT JOIN users ON activities.owner_type = 'User' AND
                            activities.owner_id = users.id").
  joins("LEFT JOIN managers ON activities.owner_type = 'Manager' AND
                               activities.owner_id = managers.id").
  where("users.visible = ? OR managers.visible = ?", true, true)