---
title: Progress.PublishingHandler
framework: foundation
role: symbol
role_heading: Type Alias
path: foundation/progress/publishinghandler
---

# Progress.PublishingHandler

A block that the system calls when an observed progress object matches the subscription.

## Declaration

```swift
typealias PublishingHandler = @Sendable (Progress) -> Progress.UnpublishingHandler?
```

## Parameters

- `progress`: The proxy to the observed progress object.

## Return Value

Return Value An optional block that the system invokes when the observed progress object invokes unpublish(), the publishing process terminates, or you invoke removeSubscriber(_:).

## See Also

### Observing and Controlling File Progress by Other Processes

- [addSubscriber(forFileURL:withPublishingHandler:)](foundation/progress/addsubscriber(forfileurl:withpublishinghandler:).md)
- [removeSubscriber(_:)](foundation/progress/removesubscriber(_:).md)
- [isOld](foundation/progress/isold.md)
- [Progress.UnpublishingHandler](foundation/progress/unpublishinghandler.md)