# map(_:) Publishes the value of a key path. ``` func map(_ keyPath: KeyPath) -> Publishers.MapKeyPath ``` ## Parameters `keyPath` The key path of a property on `Output`. ## Return Value A publisher that publishes the value of the key path. ## Discussion In the following example, the [`map(_:)`](/documentation/Combine/Publisher/map(_:)-6sm0a) operator uses the Swift key path syntax to access the `die` member of the `DiceRoll` structure published by the [`Just`](/documentation/Combine/Just) publisher. The downstream sink subscriber receives only the value of this `Int`, not the entire `DiceRoll`. ``` struct DiceRoll { let die: Int } cancellable = Just(DiceRoll(die:Int.random(in:1...6))) .map(\.die) .sink { print ("Rolled: \($0)") } // Prints "Rolled: 3" (or some other random value). ``` --- 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)