# flatMap(_:) Returns the non-`nil` results of mapping the given transformation over this sequence. ``` func flatMap(_ transform: @escaping (Self.Elements.Element) -> ElementOfResult?) -> LazyMapSequence>, ElementOfResult> ``` ## Parameters `transform` A closure that accepts an element of this sequence as its argument and returns an optional value. ## Discussion Use this method to receive a sequence of non-optional values when your transformation produces an optional value. > Complexity: O(1) --- 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)