---
title: Publishers.MapError
framework: combine
role: symbol
role_heading: Structure
path: combine/publishers/maperror
---

# Publishers.MapError

A publisher that converts any failure from the upstream publisher into a new error.

## Declaration

```swift
struct MapError<Upstream, Failure> where Upstream : Publisher, Failure : Error
```

## Topics

### Creating an error-mapping publisher

- [init(upstream:_:)](combine/publishers/maperror/init(upstream:_:).md)
- [init(upstream:transform:)](combine/publishers/maperror/init(upstream:transform:).md)

### Declaring supporting types

- [Publishers.MapError.Output](combine/publishers/maperror/output.md)

### Inspecting publisher properties

- [upstream](combine/publishers/maperror/upstream.md)
- [transform](combine/publishers/maperror/transform.md)

## Relationships

### Conforms To

- [Publisher](combine/publisher.md)

## See Also

### Mapping elements

- [Publishers.Map](combine/publishers/map.md)
- [Publishers.TryMap](combine/publishers/trymap.md)
- [Publishers.Scan](combine/publishers/scan.md)
- [Publishers.TryScan](combine/publishers/tryscan.md)
- [Publishers.SetFailureType](combine/publishers/setfailuretype.md)