iPhone SDK: How can I create a circular slider in interface builder?

开发者_如何学GoHow can I create a circular slider in interface builder? Or code if needed?

Thank you.

There is no such control in UIKit out of the box. You'll have to create your own.

The way this is done in music applications, the panning control in GarageBand for example, is by rotating an image of a knob when the knob is dragged--rotate right when dragged up and rotate left when dragged down. You could do the same in a custom UIView. Just capture the touches and see if the user is swiping up or down. Then rotate the image accordingly.