# addItem(_:) Adds a dynamic item to the collision behavior’s item array. ``` func addItem(_ item: any UIDynamicItem) ``` ## Parameters `item` The dynamic item to add to the item array. ## Discussion You can add a dynamic item to one or more collision behaviors. For example, you can use two collision behaviors to specify that item *A* can collide with item *B* and that item *C* can collide with item *D*, but that items *A* and *B* ignore items *C* and *D*. There is no hard limit to the number of dynamic items you can add to a collision behavior. However, adding a large number of items might result in a performance impact. Be sure to test your behaviors on the device configurations you are targeting. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)