---
title: "scan(_:_:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/optional/publisher-swift.struct/scan(_:_:)"
---

# scan(_:_:)

## Declaration

```swift
func scan<T>(_ initialResult: T, _ nextPartialResult: (T, Optional<Wrapped>.Publisher.Output) -> T) -> Optional<T>.Publisher
```