<!--
{
  "documentType" : "article",
  "framework" : "Combine",
  "identifier" : "/documentation/Combine/Just-Publisher-Operators",
  "metadataVersion" : "0.1.0",
  "role" : "collectionGroup",
  "title" : "Publisher Operators"
}
-->

# Publisher Operators

Methods that create downstream publishers or subscribers to act on the elements they receive.

## Topics

### Mapping elements

[`map(_:)`](/documentation/Combine/Just/map(_:))

[`tryMap(_:)`](/documentation/Combine/Just/tryMap(_:))

[`mapError(_:)`](/documentation/Combine/Just/mapError(_:))

[`scan(_:_:)`](/documentation/Combine/Just/scan(_:_:))

[`tryScan(_:_:)`](/documentation/Combine/Just/tryScan(_:_:))

[`setFailureType(to:)`](/documentation/Combine/Just/setFailureType(to:))

### Filtering elements

[`filter(_:)`](/documentation/Combine/Just/filter(_:))

[`compactMap(_:)`](/documentation/Combine/Just/compactMap(_:))

[`removeDuplicates()`](/documentation/Combine/Just/removeDuplicates())

[`removeDuplicates(by:)`](/documentation/Combine/Just/removeDuplicates(by:))

[`tryRemoveDuplicates(by:)`](/documentation/Combine/Just/tryRemoveDuplicates(by:))

[`replaceEmpty(with:)`](/documentation/Combine/Just/replaceEmpty(with:))

[`replaceError(with:)`](/documentation/Combine/Just/replaceError(with:))

### Reducing elements

[`collect()`](/documentation/Combine/Just/collect())

[`ignoreOutput()`](/documentation/Combine/Just/ignoreOutput())

[`reduce(_:_:)`](/documentation/Combine/Just/reduce(_:_:))

[`tryReduce(_:_:)`](/documentation/Combine/Just/tryReduce(_:_:))

### Applying mathematical operations on elements

[`count()`](/documentation/Combine/Just/count())

[`max()`](/documentation/Combine/Just/max())

[`max(by:)`](/documentation/Combine/Just/max(by:))

[`min()`](/documentation/Combine/Just/min())

[`min(by:)`](/documentation/Combine/Just/min(by:))

### Applying matching criteria to elements

[`contains(_:)`](/documentation/Combine/Just/contains(_:))

[`contains(where:)`](/documentation/Combine/Just/contains(where:))

[`tryContains(where:)`](/documentation/Combine/Just/tryContains(where:))

[`allSatisfy(_:)`](/documentation/Combine/Just/allSatisfy(_:))

[`tryAllSatisfy(_:)`](/documentation/Combine/Just/tryAllSatisfy(_:))

### Applying sequence operations to elements

[`dropFirst(_:)`](/documentation/Combine/Just/dropFirst(_:))

[`drop(while:)`](/documentation/Combine/Just/drop(while:))

[`append(_:)`](/documentation/Combine/Just/append(_:)-7eyqj)

[`append(_:)`](/documentation/Combine/Just/append(_:)-7sxlu)

[`prepend(_:)`](/documentation/Combine/Just/prepend(_:)-39e57)

[`prepend(_:)`](/documentation/Combine/Just/prepend(_:)-7fg73)

[`prefix(_:)`](/documentation/Combine/Just/prefix(_:))

[`prefix(while:)`](/documentation/Combine/Just/prefix(while:))

### Selecting specific elements

[`first()`](/documentation/Combine/Just/first())

[`first(where:)`](/documentation/Combine/Just/first(where:))

[`last()`](/documentation/Combine/Just/last())

[`last(where:)`](/documentation/Combine/Just/last(where:))

[`output(at:)`](/documentation/Combine/Just/output(at:))

[`output(in:)`](/documentation/Combine/Just/output(in:))

### Handling errors

[`retry(_:)`](/documentation/Combine/Just/retry(_:))


---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)