---
title: boundaryIdentifiers
framework: uikit
role: symbol
role_heading: Instance Property
path: uikit/uicollisionbehavior/boundaryidentifiers
---

# boundaryIdentifiers

The set of boundary identifiers that you’ve added to the collision behavior.

## Declaration

```swift
var boundaryIdentifiers: [any NSCopying]? { get }
```

## Discussion

Discussion If you haven’t added any boundary identifiers to the collision behavior, this property’s value is nil.

## See Also

### Configuring a collision behavior

- [addBoundary(withIdentifier:for:)](uikit/uicollisionbehavior/addboundary(withidentifier:for:).md)
- [addBoundary(withIdentifier:from:to:)](uikit/uicollisionbehavior/addboundary(withidentifier:from:to:).md)
- [boundary(withIdentifier:)](uikit/uicollisionbehavior/boundary(withidentifier:).md)
- [collisionMode](uikit/uicollisionbehavior/collisionmode.md)
- [removeAllBoundaries()](uikit/uicollisionbehavior/removeallboundaries().md)
- [removeBoundary(withIdentifier:)](uikit/uicollisionbehavior/removeboundary(withidentifier:).md)
- [setTranslatesReferenceBoundsIntoBoundary(with:)](uikit/uicollisionbehavior/settranslatesreferenceboundsintoboundary(with:).md)
- [translatesReferenceBoundsIntoBoundary](uikit/uicollisionbehavior/translatesreferenceboundsintoboundary.md)