问题在底部，但代码描述了它的大部分内容：）
这是代码的基础，缩短为了它的核心：
ActiveRecord::Base.class_eval do
def self.joins(*others)
has_many :parent_join_models, :as => :child
has_many :child_join_models, :as => :parent
options = others.extract_options!
through = (options[:as] || :parent).to_s + "_join_models"
others.each do |other|
has_many other, :through => through.to_sym
end
end
end
class Group < ActiveRecord::Base
joins :images, :class_name => "Image", :as => :parent
joins :photos, :class_name => "Image", :as => :parent
end
class SubGroup < ActiveRecord::Base
joins :pictures, :class_name => "Image", :as => :parent
end
class Image < ActiveRecord::Base
end
class JoinModel
belongs_to :parent, :polymorphic => true
belongs_to :child, :polymorphic => true
end
这就是你使用它时会发生的事情：
group = Group.create!
subgroup = SubGroup.create!
image = Image.create!
group.images << image
puts JoinModel.all
#=> [#<JoinModel id: 1, parent_id: 1, parent_type: "Group", child_id: 1, child_type: "Image">]
JoinModel.destroy_all
subgroup.images << image
puts JoinModel.all
#=> [#<JoinModel id: 2, parent_id: 1, parent_type: "Group", child_id: 1, child_type: "Image">]
我的问题是，当我通过subgroup.images << image与其关联的子类创建该联接模型时，我会如何做到这一点，它会说parent_type: "SubGroup"而不是Group？我从来没能弄明白这一点。
更新
如果我在ActiveRecord核心中改变这一行，它可以完美地运行：
module ActiveRecord
module Associations
class HasManyThroughAssociation < HasManyAssociation
protected
def construct_owner_attributes(reflection)
if as = reflection.options[:as]
{ "#{as}_id" => @owner.id,
# CHANGE 'class.base_class' to 'class'
"#{as}_type" => @owner.class.base_class.name.to_s }
else
{ reflection.primary_key_name => @owner.id }
end
end
end
end
end
......这是一个错误吗？