# scan(_:_:) Transforms elements from the upstream publisher by providing the current element to a closure along with the last value returned by the closure. ``` func scan(_ initialResult: T, _ nextPartialResult: @escaping (T, Self.Output) -> T) -> Publishers.Scan ``` ## Parameters `initialResult` The previous result returned by the `nextPartialResult` closure. `nextPartialResult` A closure that takes as its arguments the previous value returned by the closure and the next element emitted from the upstream publisher. ## Return Value A publisher that transforms elements by applying a closure that receives its previous return value and the next element from the upstream publisher. ## Discussion Use [`scan(_:_:)`](/documentation/Combine/Publisher/scan(_:_:)) to accumulate all previously-published values into a single value, which you then combine with each newly-published value. The following example logs a running total of all values received from the sequence publisher. ``` let range = (0...5) cancellable = range.publisher .scan(0) { return $0 + $1 } .sink { print ("\($0)", terminator: " ") } // Prints: "0 1 3 6 10 15 ". ``` --- 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)