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# init(duration:animationCurve:)

Returns an `NSAnimation` object initialized with the specified duration and animation-curve values.

```
init(duration: TimeInterval, animationCurve: NSAnimation.Curve)
```

## Parameters

`duration`

The number of seconds over which the animation occurs. Specifying a negative number raises an exception.

`animationCurve`

An `NSAnimationCurve` constant that describes the relative speed of the animation over its course; if it is zero, the default curve (`NSAnimationEaseInOut`) is used.

## Return Value

An initialized `NSAnimation` instance. Returns `nil` if the object could not be initialized.

## Discussion

You can always later change the duration of an `NSAnimation` object by changing the [`duration`](/documentation/AppKit/NSAnimation/duration) property, even while the animation is running. See “Constants” for descriptions of the NSAnimationCurve constants.

## See Also

[Drawing](/documentation/AppKit/drawing)

Draw shapes, images, and other content on the screen.

[`NSAnimation`](/documentation/AppKit/NSAnimation)

An object that manages the timing and progress of animations in the user interface.


---

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