CABasicAnimation - Animating between two angles

问题:

I'm attempting to create an animated CALayer that uses a CABasicAnimation in order to animate an object that rotates at discrete intervals between two angles. Note the word discrete: I'm not trying to create a continuous animation between two points, but rather I want to calculate fixed increments between each angle in order to create a discrete movement feel.

Here's a diagram:

I've looked into setting the byValue attribute of the CABasicAnimation, but I can't seem to get it to work since you can't use fromValue, ToValue, and byValue in one animation. fromValue is always from zero, so I guess that could be dropped, but it still never animates correctly when using the current endAngle as the toValue and a byValue of 0.1 (arbitrarily chosen but should work for testing). Any ideas on how to implement this? Here's code I'm using:

anim = [CABasicAnimation animationWithKeyPath:@"currentEndAngle"];
anim.duration = 0.5f;
anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
anim.toValue = [NSNumber numberWithFloat:self.endAngle];
anim.byValue = [NSNumber numberWithFloat:0.1f];
anim.repeatCount = HUGE_VALF;
[anim setDelegate:self];
[self addAnimation:anim forKey:@"animKey"];

Thanks!