# compactMap(_:) Calls a closure with each received element and publishes any returned optional that has a value. ``` func compactMap(_ transform: @escaping (Self.Output) -> T?) -> Publishers.CompactMap ``` ## Parameters `transform` A closure that receives a value and returns an optional value. ## Return Value Any non-`nil` optional results of the calling the supplied closure. ## Discussion Combine’s [`compactMap(_:)`](/documentation/Combine/Publisher/compactMap(_:)) operator performs a function similar to that of in the Swift standard library: the [`compactMap(_:)`](/documentation/Combine/Publisher/compactMap(_:)) operator in Combine removes `nil` elements in a publisher’s stream and republishes non-`nil` elements to the downstream subscriber. The example below uses a range of numbers as the source for a collection based publisher. The [`compactMap(_:)`](/documentation/Combine/Publisher/compactMap(_:)) operator consumes each element from the `numbers` publisher attempting to access the dictionary using the element as the key. If the example’s dictionary returns a `nil`, due to a non-existent key, [`compactMap(_:)`](/documentation/Combine/Publisher/compactMap(_:)) filters out the `nil` (missing) elements. ``` let numbers = (0...5) let romanNumeralDict: [Int : String] = [1: "I", 2: "II", 3: "III", 5: "V"] cancellable = numbers.publisher .compactMap { romanNumeralDict[$0] } .sink { print("\($0)", terminator: " ") } // Prints: "I II III V" ``` --- 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)