---
title: "setFailureType(to:)"
framework: combine
role: symbol
role_heading: Instance Method
path: "combine/publisher/setfailuretype(to:)"
---

# setFailureType(to:)

Changes the failure type declared by the upstream publisher.

## Declaration

```swift
func setFailureType<E>(to failureType: E.Type) -> Publishers.SetFailureType<Self, E> where E : Error
```

## Parameters

- `failureType`: The Failure type presented by this publisher.

## Return Value

Return Value A publisher that appears to send the specified failure type.

## Discussion

Discussion Use setFailureType(to:) when you need set the error type of a publisher that cannot fail. Conversely, if the upstream can fail, you would use mapError(_:) to provide instructions on converting the error types to needed by the downstream publisher’s inputs. The following example has two publishers with mismatched error types: pub1’s error type is Never, and pub2’s error type is Error. Because of the mismatch, the combineLatest(_:) operator requires that pub1 use setFailureType(to:) to make it appear that pub1 can produce the Error type, like pub2 can. let pub1 = [0, 1, 2, 3, 4, 5].publisher let pub2 = CurrentValueSubject<Int, Error>(0) let cancellable = pub1     .setFailureType(to: Error.self)     .combineLatest(pub2)     .sink(         receiveCompletion: { print ("completed: \($0)") },         receiveValue: { print ("value: \($0)")}      )

// Prints: "value: (5, 0)".

## See Also

### Mapping elements

- [map(_:)](combine/publisher/map(_:)-99evh.md)
- [tryMap(_:)](combine/publisher/trymap(_:).md)
- [mapError(_:)](combine/publisher/maperror(_:).md)
- [replaceNil(with:)](combine/publisher/replacenil(with:).md)
- [scan(_:_:)](combine/publisher/scan(_:_:).md)
- [tryScan(_:_:)](combine/publisher/tryscan(_:_:).md)