Textfield automatically get the focus on the issue

There are two textfield in my application, named t1, t2 bar, have limited the only enter three digits, I now want the user to enter a 3 t1 in digital, automatic focus jump t2, I how to write code? ? I learn new iphone, thanks to Daniel who gets advice
Reply:
This implementation is very simple.
You still look at the spectacle of documents, delegate, familiarize yourself with the concepts and behaviors, mvc etc.
Reply:
By a floor to do it, textfield corresponding delegate methods to meet the requirements after the call the appropriate method respond or what Apple help documentation is good.