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# animation(forKey:)

Returns the animation that should be performed for the specified key.

```
func animation(forKey key: NSAnimatablePropertyKey) -> Any?
```

## Parameters

`key`

The action name or property specified as a string.

## Return Value

The animation to perform. A subclass of <doc://com.apple.documentation/documentation/QuartzCore/CAAnimation>.

## Discussion

When the action specified by `key` is triggered for an object, this method is consulted to find the animation, if any, that should be performed in response.

Like its Core Animation <doc://com.apple.documentation/documentation/QuartzCore/CALayer> counterpart, <doc://com.apple.documentation/documentation/QuartzCore/CALayer/action(forKey:)>, this method is a funnel point that defines the order in which the search for an animation proceeds.It first checks the receiver’s Getting the Animator Proxy dictionary for a value matching `key`, then falls back to  [`animator()`](/documentation/AppKit/NSAnimatablePropertyContainer/animator()) for the receiver’s class.

Subclasses should not typically need to override this method.

## See Also

[`-  animator`](/documentation/AppKit/NSAnimatablePropertyContainer/animator())

Returns a proxy object for the receiver that can be used to initiate implied animation for property changes.


---

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