CAKeyframeAnimation Manual Progress - ios

Question

I have a UIView whose backing layer has a CAKeyframeAnimation with a simple straight line path set as its `path`.
Can I have the animation "frozen", so to speak, and manually change its progress?
For example:
If the path is 100 points in length, setting the progress (offset?) to 0.45 should have the view move 45 points down the path.
I remember seeing an article that did something similar (moving a view along a path based on the value from a slider) via CAMediaTiming interfaces, but I haven't been able to find it, even after a few hours of searching. If I'm approaching this in a completely wrong way, please do let me know. Thanks.
Here's some sample code, if the above isn't clear enough.
- (void)setupAnimation
{
CAKeyFrameAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:#"position"];
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:_label.layer.position];
[path addLineToPoint:(CGPoint){200, 200}];
animation.path = path.CGPath;
animation.duration = 1;
animation.autoreverses = NO;
animation.removedOnCompletion = NO;
animation.speed = 0;
// _label is just a UILabel in a storyboard
[_label.layer addAnimation:animation forKey:#"LabelPathAnimation"];
}
- (void)sliderDidSlide:(UISlider *)slider
{
// move _label along _animation.path for a distance that corresponds to slider.value
}

Answer 1

This is based on what Jonathan said, only a bit more to the point. The animation is set up correctly, but the slider action method should be as follows:
- (void)sliderDidSlide:(UISlider *)slider
{
// Create and configure a new CAKeyframeAnimation instance
CAKeyframeAnimation *animation = ...;
animation.duration = 1.0;
animation.speed = 0;
animation.removedOnCompletion = NO;
animation.timeOffset = slider.value;
// Replace the current animation with a new one having the desired timeOffset
[_label.layer addAnimation:animation forKey:#"LabelPathAnimation"];
}
This will make the label move along the animation's path based on timeOffset.

Answer 2

Yes you can do this with the CAMediaTiming interface. You can set the speed of the layer to 0 and manualy set the timeOffset. Example of a simple pause/resume method:
- (void)pauseAnimation {
CFTimeInterval pausedTime = [yourLayer convertTime:CACurrentMediaTime() fromLayer:nil];
yourLayer.speed = 0.0;
yourLayer.timeOffset = pausedTime;
}
- (void)resumeAnimation {
CFTimeInterval pausedTime = [yourLaye timeOffset];
if (pausedTime != 0) {
yourLayer.speed = 1.0;
yourLayer.timeOffset = 0.0;
yourLayer.beginTime = 0.0;
CFTimeInterval timeSincePause = [yourLayer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
yourLayer.beginTime = timeSincePause;
}
}