# max(by:) Returns the maximum element in the sequence, using the given predicate as the comparison between elements. ``` @warn_unqualified_access func max(by areInIncreasingOrder: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element? ``` ## Parameters `areInIncreasingOrder` A predicate that returns `true` if its first argument should be ordered before its second argument; otherwise, `false`. ## Return Value The sequence’s maximum element if the sequence is not empty; otherwise, `nil`. ## Discussion The predicate must be a *strict weak ordering* over the elements. That is, for any elements `a`, `b`, and `c`, the following conditions must hold: - `areInIncreasingOrder(a, a)` is always `false`. (Irreflexivity) - If `areInIncreasingOrder(a, b)` and `areInIncreasingOrder(b, c)` are both `true`, then `areInIncreasingOrder(a, c)` is also `true`. (Transitive comparability) - Two elements are *incomparable* if neither is ordered before the other according to the predicate. If `a` and `b` are incomparable, and `b` and `c` are incomparable, then `a` and `c` are also incomparable. (Transitive incomparability) This example shows how to use the `max(by:)` method on a dictionary to find the key-value pair with the highest value. ``` let hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156] let greatestHue = hues.max { a, b in a.value < b.value } print(greatestHue) // Prints "Optional((key: "Heliotrope", value: 296))" ``` > Complexity: O(*n*), where *n* is the length of the sequence. --- 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)