Rails - Apr 2006 - How to use polymorphic in a beautiful way in such a case?

class User<ActiveRecord::Base
has_many :taggings, :as=>:taggable,:dependent=>true
has_many :tags,:through=>:taggings
end
class Article<ActiveRecord::Base
has_many :taggings, :as=>:taggable,:dependent=>true
has_many :tags,:through=>:taggings
end
class Tagging<ActiveRecord::Base
belongs_to :tag
belongs_to :taggable,:polymorphic=>true
end
class Tag<ActiveRecord::Base
has_many :taggings
def tagged
  taggings.collect{|tagging| tagging.taggable}
end
...
end

The above code is something like acts_as_taggable plugin.
Now I want this function:Given a tag,then list all the articles that has 
such a tag.Traditionally,the plugin just provides attaching tags to 
users and articles,but this function need the reverse relation.
The provided "tagged" function:
david=User.find(...)
john=User.find(...)
welcome=Article.find(1)
...
then "david" has tag "summer" and "john"
,"welcome" also have the tag
"summer"

summer.tagged #=>[david,john,welcome]

I only want to get david,john while not welcome

now I have to do that using find_by_sql,very ugly,is there a good way?


Thanks
Charlie

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