It is not quite clear what you are trying to do. But it seems like you
are reinventing a square wheel 
Did you try some ready solutions like http://github.com/mbleigh/acts-as-taggable-on/
?
Regards
It is not quite clear what you are trying to do. But it seems like you
are reinventing a square wheel
Did you try some ready solutions like http://github.com/mbleigh/acts-as-taggable-on/
?
Regards