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# Publishers.TryScan

A publisher that transforms elements from the upstream publisher by providing the current element to a failable closure along with the last value returned by the closure.

```
struct TryScan<Upstream, Output> where Upstream : Publisher
```

## Topics

### Creating a try-scan publisher

[`init(upstream:initialResult:nextPartialResult:)`](/documentation/Combine/Publishers/TryScan/init(upstream:initialResult:nextPartialResult:))

Creates a publisher that transforms elements from the upstream publisher by providing the current element to a failable closure along with the last value returned by the closure.

### Declaring supporting types

[`Publishers.Output`](/documentation/Combine/Publishers/Output)

A publisher that publishes elements specified by a range in the sequence of published elements.

[`Publishers.TryScan.Failure`](/documentation/Combine/Publishers/TryScan/Failure)

The kind of errors this publisher might publish.

### Inspecting publisher properties

[`upstream`](/documentation/Combine/Publishers/TryScan/upstream)

The publisher that this publisher receives elements from.

[`initialResult`](/documentation/Combine/Publishers/TryScan/initialResult)

The previous result returned by the `nextPartialResult` closure.

[`nextPartialResult`](/documentation/Combine/Publishers/TryScan/nextPartialResult)

An error-throwing closure that takes as its arguments the previous value returned by the closure and the next element emitted from the upstream publisher.


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