# flatMap(_:) Returns a new result, mapping any success value using the given transformation and unwrapping the produced result. ``` func flatMap(_ transform: (Success) -> Result) -> Result where NewSuccess : ~Copyable ``` ## Parameters `transform` A closure that takes the success value of the instance. ## Return Value A `Result` instance, either from the closure or the previous `.failure`. ## Discussion Use this method to avoid a nested result when your transformation produces another `Result` type. In this example, note the difference in the result of using `map` and `flatMap` with a transformation that returns a result type. ``` func getNextInteger() -> Result { .success(4) } func getNextAfterInteger(_ n: Int) -> Result { .success(n + 1) } let result = getNextInteger().map { getNextAfterInteger($0) } // result == .success(.success(5)) let result = getNextInteger().flatMap { getNextAfterInteger($0) } // result == .success(5) ``` --- 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)