shouldMerge(previous:value:time:context:)

Declaration

nonisolated func shouldMerge<V>(previous: Animation, value: V, time: TimeInterval, context: inout AnimationContext<V>) -> Bool where V : VectorArithmetic

Parameters

• previous:

  The previous running animation.

• value:

  The vector to animate towards.

• time:

  The amount of time since the start of the previous animation.

• context:

  An instance of Animationcontext that provides access to state and the animation environment.

Return Value

A Boolean value of true if the animation should merge with the previous animation; otherwise, false.

Discussion

When a view creates a new animation on an animatable value that already has a running animation of the same animation type, the system calls the shouldMerge(previous:value:time:context:) method on the new instance to determine whether it can merge the two instance. Implement this method if the animation can merge with another instance. The default implementation returns false.

If shouldMerge(previous:value:time:context:) returns true, the system merges the new animation instance with the previous animation. The system provides to the new instance the state and elapsed time from the previous one. Then it removes the previous animation.

If this method returns false, the system doesn’t merge the animation with the previous one. Instead, both animations run together and the system combines their results.

If your custom animation needs to maintain state between calls to the shouldMerge(previous:value:time:context:) method, store the state data in context. This makes the data available to the method next time the system calls it. To learn more, see AnimationContext.