# lastIndex(where:) Returns the index of the last element in the collection that matches the given predicate. ``` func lastIndex(where predicate: (Self.Element) throws -> Bool) rethrows -> Self.Index? ``` ## Parameters `predicate` A closure that takes an element as its argument and returns a Boolean value that indicates whether the passed element represents a match. ## Return Value The index of the last element in the collection that matches `predicate`, or `nil` if no elements match. ## Discussion You can use the predicate to find an element of a type that doesn’t conform to the `Equatable` protocol or to find an element that matches particular criteria. This example finds the index of the last name that begins with the letter *A:* ``` let students = ["Kofi", "Abena", "Peter", "Kweku", "Akosua"] if let i = students.lastIndex(where: { $0.hasPrefix("A") }) { print("\(students[i]) starts with 'A'!") } // Prints "Akosua starts with 'A'!" ``` > Complexity: O(*n*), where *n* is the length of the collection. --- 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)