ruby-on-rails – 查询多态关联

class Image < ActiveRecord::Base
  has_one :approval,:as => :approvable
end

class Page < ActiveRecord::Base
  has_one :approval,:as => :approvable
end

class Site < ActiveRecord::Base
  has_one :approval,:as => :approvable
end

class Approval < ActiveRecord::Base
  belongs_to :approvable,:polymorphic => true
end

我需要在approval.apporvable.deleted = false的地方找到批准

我尝试过这样的事情 –

@approvals = Approval.find(:all,:include => [:approvable],:conditions => [":approvable.deleted = ?",false ])

这给出了“无法急切加载多态关联：可批准”的错误

如何正确地给出条件,以便我得到一个带有批准的结果集谁没有删除可批准的项目？

在此先感谢您的帮助