Transforms elements from the upstream publisher by providing the current element to a closure along with the last value returned by the closure.
SDKs
- iOS 13.0+
- macOS 10.15+
- Mac Catalyst 13.0+
- tvOS 13.0+
- watchOS 6.0+
- Xcode 11.0+
Framework
- Combine
Declaration
func scan<T>(_ initialResult: T, _ nextPartialResult: @escaping (T, Output) -> T) -> Publishers.Scan<Publishers.Map<Upstream, Output>, T>
Parameters
initialResultThe previous result returned by the
nextclosure.Partial Result nextPartialResultA 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
let pub = (0...5)
.publisher()
.scan(0, { return $0 + $1 })
.sink(receiveValue: { print ("\($0)", terminator: " ") })
// Prints "0 1 3 6 10 15 ".