如何让View一直沿z轴旋转

#import <QuartzCore/QuartzCore.h>
...

CABasicAnimation *rotationAni = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
rotationAni.toValue = [NSNumber numberWithFloat:M_PI*2];
rotationAni.duration = 0.5;
rotationAni.cumulative = YES;
rotationAni.repeatCount = 10000;
[indicatorView.layer addAnimation:rotationAni forKey:@"rotationAnimation1"];