gistfile1.m

void performAnimation(UIView *view, CGFloat angle, CGFloat targetAngle);
void performAnimation(UIView *view, CGFloat angle, CGFloat targetAngle) {
    [UIView animateWithDuration:1 delay:0 options:UIViewAnimationCurveEaseOut animations:^(void) {
        [view setTransform:CGAffineTransformMakeRotation(angle)];
    } completion:^(BOOL finished) {
        if (targetAngle > M_PI_4) {
            performAnimation(view, angle + M_PI_4, targetAngle - M_PI_4);
        } else 
            if (targetAngle > 0) {
                performAnimation(view, targetAngle, 0);
            }
    }];
}


...
    performAnimation(self.imageView, M_PI_4, 10 * M_PI_2);