gistfile1.m

CALayer* layer = someView.layer;
CAKeyframeAnimation* animation;
animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

animation.duration = 1.0;
animation.cumulative = YES;
animation.repeatCount = 1;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;

animation.values = [NSArray arrayWithObjects:
    [NSNumber numberWithFloat:0.0 * M_PI],
    [NSNumber numberWithFloat:0.5 * M_PI],
    [NSNumber numberWithFloat:1.0 * M_PI], nil];

animation.keyTimes = [NSArray arrayWithObjects:
    [NSNumber numberWithFloat:0.0],
    [NSNumber numberWithFloat:0.5],
    [NSNumber numberWithFloat:1.0], nil];

animation.timingFunctions = [NSArray arrayWithObjects:
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear], nil];

[layer addAnimation:animation forKey:@"transform.rotation.z"];