Layer Time - iOS Core Animation - page 209

//reset pan gesture
[pan setTranslation : CGPointZero inView : self . view ];
}
@end
That's a neat trick, but you might be thinking that it would be easier to just set the door's
transform directly using our pan gesture, rather than setting up an animation and then only
displaying a single frame at a time.
That is true in this simple case, but for a more complex case such as a keyframe animation,
or an animation group with several moving layers, this is actually a very simple way to
scrub through the animation without having to manually calculate each property of every
layer at a given point in time.
Summary
In this chapter, you learned about the CAMediaTiming protocol and the mechanisms that
Core Animation uses to manipulate time for the purposes of controlling animations. In the
next chapter, we cover easing , another time-manipulation technique used to make
animations appear more natural.