# init(upstream:predicate:) Creates a publisher that publishes only elements that don’t match the previous element, as evaluated by a provided error-throwing closure. ``` init(upstream: Upstream, predicate: @escaping (Publishers.TryRemoveDuplicates.Output, Publishers.TryRemoveDuplicates.Output) throws -> Bool) ``` ## Parameters `upstream` The publisher from which this publisher receives elements. `predicate` An error-throwing closure to evaluate whether two elements are equivalent, for purposes of filtering. Return `true` from this closure to indicate that the second element is a duplicate of the first. If this closure throws an error, the publisher terminates with the thrown error. --- 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)