Many-To-Many relation - Creating all models in the same form


I want to create a screen similar to the delicious one, where you can
assign tags dynamically

to the bookmarks, but I don't have the tags neither the bookmark
created before the submit, and

all approaches that i tried resulted in the following error:

"Cannot associate new records through 'Bookmark#taggings' on '#'.
Both records must have an id in order to create the has_many :through
record associating them."

Any body have an example or any insights about that?

I think my approach will be use a plugin for taggables models, but I
want to understand how to do

this in case I have another kind of many-to-many.

Regards, Felipe Lopes

It was limitation of has many through until rails 2.1


should be update rails my approach?

should it start working after an update?