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# collisionBoundsType

The type of collision bounds associated with the item.

```
optional var collisionBoundsType: UIDynamicItemCollisionBoundsType { get }
```

## Discussion

The dynamics system uses this property to determine how to evaluate collisions with the dynamic item. Rectangular and elliptical bounds are defined by the [`bounds`](/documentation/UIKit/UIDynamicItem/bounds) property of the item. For custom collision bounds, the shape of the bounds are in the [`collisionBoundingPath`](/documentation/UIKit/UIDynamicItem/collisionBoundingPath) property.

If you implement this property in your dynamic item and set its value to [`UIDynamicItemCollisionBoundsType.path`](/documentation/UIKit/UIDynamicItemCollisionBoundsType/path), you must also implement the [`collisionBoundingPath`](/documentation/UIKit/UIDynamicItem/collisionBoundingPath) property and provide a valid path. Failure to do so is a programmer error.

The default value of this property is [`UIDynamicItemCollisionBoundsType.rectangle`](/documentation/UIKit/UIDynamicItemCollisionBoundsType/rectangle).

---

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