# tryMax(by:) Publishes the maximum value received from the upstream publisher, using the provided error-throwing closure to order the items. ``` func tryMax(by areInIncreasingOrder: @escaping (Self.Output, Self.Output) throws -> Bool) -> Publishers.TryComparison ``` ## Parameters `areInIncreasingOrder` A throwing closure that receives two elements and returns `true` if they’re in increasing order. If this closure throws, the publisher terminates with a [`Subscribers.Completion.failure(_:)`](/documentation/Combine/Subscribers/Completion/failure(_:)). ## Return Value A publisher that publishes the maximum value received from the upstream publisher, after the upstream publisher finishes. ## Discussion Use [`tryMax(by:)`](/documentation/Combine/Publisher/tryMax(by:)) to determine the maximum value of elements received from the upstream publisher using an error-throwing closure you specify. In the example below, an array publishes elements. The [`tryMax(by:)`](/documentation/Combine/Publisher/tryMax(by:)) operator executes the error-throwing closure that throws when the `first` element is an odd number, terminating the publisher. ``` struct IllegalValueError: Error {} let numbers: [Int] = [0, 10, 6, 13, 22, 22] cancellable = numbers.publisher .tryMax { first, second -> Bool in if (first % 2 != 0) { throw IllegalValueError() } return first > second } .sink( receiveCompletion: { print ("completion: \($0)") }, receiveValue: { print ("value: \($0)") } ) // Prints: completion: failure(IllegalValueError()) ``` After this publisher receives a request for more than 0 items, it requests unlimited items from its upstream publisher. --- 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)