I am new to IPhone SDK development.

I created a circle with CGContextAddEllipseInRect() and It is working fine.
I have some other view (ball) which I want to move inside the circle randomly (Random moving I did already).
What I want is , If Ball view touches the circle line it has to move back.

How can I know the whether the ball touches the circle line or not ?

I searched a lot on the net but no luck ?

Thank You,