Help needed regarding Yahoo autocomplete UI in rails

HI guys,
I have a tag field in my rails app.
I want to add auto complete option in tag input field by yahoo UI.
I have googled a lot but nothing found workable.
Here is the best one that I found from net but by protype.

I have tried with prototype also but not work for me.
But when I type in the tag field nothing is shown.
Please help me about it. any example or tutorial will be great.