Instance MethodSwift


    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?



    A predicate that returns true if its first argument should be ordered before its second argument; otherwise, false.


    The sequence’s maximum element if the sequence is not empty; otherwise, nil.


    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 }
    // Prints "Optional((key: "Heliotrope", value: 296))"