Let user reorder buttons in a UIView

I have a view in which there are 6 buttons. I want to let user reorder the position of these buttons as I can do in the screen of the iphone with the app icons. The use开发者_运维问答r could drag a button to the position of another button and change its position in the view. Facebook app has this functionality with its icons too. Any idea? Thanks.

What you are looking for is the Three20 Launcher.