# appending(path:) Returns a new key path created by appending the given key path to this one. ``` func appending(path: AnyKeyPath) -> AnyKeyPath? ``` ## Parameters `path` The key path to append. ## Return Value A key path from the root of this key path and the value type of `path`, if `path` can be appended. If `path` can’t be appended, returns `nil`. ## Discussion Use this method to extend this key path to the value type of another key path. Appending the key path passed as `path` is successful only if the root type for `path` matches this key path’s value type. This example creates key paths from `Array` to `String` and from `String` to `Int`, and then tries appending each to the other: ``` let arrayDescription: AnyKeyPath = \Array.description let stringLength: AnyKeyPath = \String.count // Creates a key path from `Array` to `Int` let arrayDescriptionLength = arrayDescription.appending(path: stringLength) let invalidKeyPath = stringLength.appending(path: arrayDescription) // invalidKeyPath == nil ``` The second call to `appending(path:)` returns `nil` because the root type of `arrayDescription`, `Array`, does not match the value type of `stringLength`, `Int`. --- 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)