---
title: "start(when:reachesProgress:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nsanimation/start(when:reachesprogress:)"
---

# start(when:reachesProgress:)

Starts running the animation represented by the receiver when another animation reaches a specific progress mark.

## Declaration

```swift
func start(when animation: NSAnimation, reachesProgress startProgress: NSAnimation.Progress)
```

## Parameters

- `animation`: The other NSAnimation object with which the receiver is linked.
- `startProgress`: A float value (typed as NSAnimationProgress) that specifies a progress mark of the other animation.

## Discussion

Discussion This method links the running of two animations together. You can set only one NSAnimation object as a start animation and one as a stop animation at any one time. Setting a new start animation removes any animation previously set.

## See Also

### Related Documentation

- [start()](appkit/nsanimation/start().md)

### Linking Animations Together

- [stop(when:reachesProgress:)](appkit/nsanimation/stop(when:reachesprogress:).md)
- [clearStart()](appkit/nsanimation/clearstart().md)
- [clearStop()](appkit/nsanimation/clearstop().md)