# map(_:) Returns an array containing the results of mapping the given closure over the sequence’s elements. ``` func map(_ transform: (Self.Element) throws(E) -> T) throws(E) -> [T] where E : Error ``` ## Parameters `transform` A mapping closure. `transform` accepts an element of this sequence as its parameter and returns a transformed value of the same or of a different type. ## Return Value An array containing the transformed elements of this sequence. ## Discussion In this example, `map` is used first to convert the names in the array to lowercase strings and then to count their characters. ``` let cast = ["Vivien", "Marlon", "Kim", "Karl"] let lowercaseNames = cast.map { $0.lowercased() } // 'lowercaseNames' == ["vivien", "marlon", "kim", "karl"] let letterCounts = cast.map { $0.count } // 'letterCounts' == [6, 6, 3, 4] ``` --- 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)