search for: _tag_with_

I''m following the acts_as_taggable chapter from the Rails Recipes book. I want my view form to have a text_field that correlates to an attribute in the Model that accepts a string of space delimited tags. The book uses tag-_list, but from what I can tell this attribute can''t be written to. I''ve added this to the plugin code itself - am I missing something, is there a