Question

我有两个表，“内容”和“个人资料”可以评论和评级。我已经看过使用多态关联并决定反对它。如果我使用多态关联，表“rating”和“comments”都会有这个功能。

这是否可以通过具体的超级实现来实现？如果是这样，我该怎么做？

Answer 1

您正在混合联接中的列。它应该是这样的：


  find(self.id, :joins => "JOIN commentables cm ON (profiles.commentable_id = cm.id) 
  LEFT OUTER JOIN comments c ON (cm.id = c.commentable_id)")

Answer 2

试试这个：


class Commentable < ActiveRecord::Base
  has_many :comments
  has_one :profile, :content
end

class Comment < ActiveRecord::Base
  belongs_to :commentable
end

class Content < ActiveRecord::Base
  belongs_to :commentable
end

class Profile < ActiveRecord::Base
  belongs_to :commentable
end

这使您能够（脚本/控制台）：


# every time you create a profile, link it to the 
# commentable row associated to this profile instance
cid = Commentable.create().id
p = Profile.create(:name => "Inspector Gadget", 
                   :commentable_id => cid)

# when creating the comment, assign the commentable_id 
# to link it to a Profile comment
Comment.new do |c|
  c.body = "go go gadget"
  c.email = "Inspector.Gadget@example.com"
  c.commentable_id = p.commentable_id
  c.save!
end

要从配置文件中检索数据库中的注释，请使用此技巧：


# Profile.rb

# instead of doing a has many through, 
# we can just use instance method with custom join.
def comments
  find(self.id, :joins => "JOIN commentables cm ON (profiles.id = cm.id) 
  LEFT OUTER JOIN comments c ON (cm.id = c.commentable_id)")
end

未经测试的代码！

请点击此处了解更多详情和解释，Why can you not have a foreign key in a polymorphic association?

Answer 3

如果我错了，请纠正我，但你不能在Profiles.rb中做到这一点


def comments
  Comments.find(:all, :conditions => ["commentable_id = ?", self.commentable_id])
end

我可以使用多个具体的超级表格来实现这一目标吗？

3 个答案: