The signature for the custom timing block.
- iOS 8.0+
- macOS 10.10+
- tvOS 9.0+
- watchOS 3.0+
The block parameters are defined as follows:
The input time, where
0represents the start time of the animation and
1represents the end time of the animation.
The input value will be a value between
1, inclusive. The block must also return a value between
1. When the input time is
0, the output value should be
0. When the input time is
1, the output value should also be