# onPreferenceChange(_:perform:) Adds an action to perform when the specified preference key’s value changes. ``` nonisolated func onPreferenceChange(_ key: K.Type = K.self, perform action: @escaping (K.Value) -> Void) -> some View where K : PreferenceKey, K.Value : Equatable ``` ## Parameters `key` The key to monitor for value changes. `action` The action to perform when the value for `key` changes. The `action` closure passes the new value as its parameter. ## Return Value A view that triggers `action` when the value for `key` changes. --- 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)