ios - CABasicAnimation中progress keypath的含义是什么？

Question

来自 https://github.com/danielamitay/DACircularProgress/blob/master/DACircularProgress/DACircularProgressView.m 的代码片段

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"progress"];
animation.duration = duration;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
animation.fillMode = kCAFillModeForwards;
animation.fromValue = [NSNumber numberWithFloat:self.progress];
animation.toValue = [NSNumber numberWithFloat:pinnedProgress];
animation.beginTime = CACurrentMediaTime() + initialDelay;
animation.delegate = self;
[self.circularProgressLayer addAnimation:animation forKey:@"progress"];

但是我找不到 progress在 offical document .键路径是否需要是可动画的属性？ progress 是什么意思意思是？

Answer 1

来自 this answer (巧合的是 progress 的动画):

Firstly we need to create a new subclass of CALayer that has an animatable property called 'progress'.

您的代码段确实有一个名为“进度”的属性

@property(nonatomic) CGFloat progress;

看来动画正在为该属性设置动画