Has_one：通过多态的belongs_to

Question

I have a Tagging model, with polymorphic associations to tags and taggable items. Taggable items all have an association to a feed_item (has_one :feed_item). I want to associate the tagging to the feed_item ie in tagging.rb

   belongs_to :taggable, :polymorphic => true
   belongs_to :tag, :polymorphic => true

   has_one :feed_item, :through => :taggable

This has_one association doesn't work. For example in console Tagging.first.feed_item leads to the error

 NameError: uninitialized constant Tagging::Taggable

Any advice to how one sets up this sort of association?

For background, the following is an example of a taggable object's model:

 has_one :feed_item, :as => :item

IE: A tagging has_one taggable object which has_one feed_item.

Answer 1

Replace this:

has_one :feed_item, :through => :taggable

with this:

def feed_item
  self.taggable.feed_item
end

Now you can call @taggable.feed_item and it'll work.

Answer 2

Can you take a look at https://github.com/rahul/SO_9288016 and let me know if it does not work for you.

I also added a tiny db/development.sqlite3