---
title: Publisher Operators
framework: combine
role: collectionGroup
role_heading: API Collection
path: combine/just-publisher-operators
---

# Publisher Operators

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

## Topics

### Mapping elements

- [map(_:)](combine/just/map(_:).md)
- [tryMap(_:)](combine/just/trymap(_:).md)
- [mapError(_:)](combine/just/maperror(_:).md)
- [scan(_:_:)](combine/just/scan(_:_:).md)
- [tryScan(_:_:)](combine/just/tryscan(_:_:).md)
- [setFailureType(to:)](combine/just/setfailuretype(to:).md)

### Filtering elements

- [filter(_:)](combine/just/filter(_:).md)
- [compactMap(_:)](combine/just/compactmap(_:).md)
- [removeDuplicates()](combine/just/removeduplicates().md)
- [removeDuplicates(by:)](combine/just/removeduplicates(by:).md)
- [tryRemoveDuplicates(by:)](combine/just/tryremoveduplicates(by:).md)
- [replaceEmpty(with:)](combine/just/replaceempty(with:).md)
- [replaceError(with:)](combine/just/replaceerror(with:).md)

### Reducing elements

- [collect()](combine/just/collect().md)
- [ignoreOutput()](combine/just/ignoreoutput().md)
- [reduce(_:_:)](combine/just/reduce(_:_:).md)
- [tryReduce(_:_:)](combine/just/tryreduce(_:_:).md)

### Applying mathematical operations on elements

- [count()](combine/just/count().md)
- [max()](combine/just/max().md)
- [max(by:)](combine/just/max(by:).md)
- [min()](combine/just/min().md)
- [min(by:)](combine/just/min(by:).md)

### Applying matching criteria to elements

- [contains(_:)](combine/just/contains(_:).md)
- [contains(where:)](combine/just/contains(where:).md)
- [tryContains(where:)](combine/just/trycontains(where:).md)
- [allSatisfy(_:)](combine/just/allsatisfy(_:).md)
- [tryAllSatisfy(_:)](combine/just/tryallsatisfy(_:).md)

### Applying sequence operations to elements

- [dropFirst(_:)](combine/just/dropfirst(_:).md)
- [drop(while:)](combine/just/drop(while:).md)
- [append(_:)](combine/just/append(_:)-7eyqj.md)
- [append(_:)](combine/just/append(_:)-7sxlu.md)
- [prepend(_:)](combine/just/prepend(_:)-39e57.md)
- [prepend(_:)](combine/just/prepend(_:)-7fg73.md)
- [prefix(_:)](combine/just/prefix(_:).md)
- [prefix(while:)](combine/just/prefix(while:).md)

### Selecting specific elements

- [first()](combine/just/first().md)
- [first(where:)](combine/just/first(where:).md)
- [last()](combine/just/last().md)
- [last(where:)](combine/just/last(where:).md)
- [output(at:)](combine/just/output(at:).md)
- [output(in:)](combine/just/output(in:).md)

### Handling errors

- [retry(_:)](combine/just/retry(_:).md)