---
title: "FSEventStreamSetDispatchQueue(_:_:)"
framework: Core Services
role: symbol
role_heading: Function
platforms: [Mac Catalyst 13.1+, macOS 10.6+]
path: coreservices/1444164-fseventstreamsetdispatchqueue
---

# FSEventStreamSetDispatchQueue(_:_:)

Schedules the stream on the specified dispatch queue.

## Declaration

```swift
func FSEventStreamSetDispatchQueue(_ streamRef: FSEventStreamRef, _ q: dispatch_queue_t?)
```

## Parameters

- `streamRef`: A valid stream.
- `q`: The dispatch queue to use to receive events (or NULL to stop receiving events from the stream).

## Discussion

Discussion The caller is responsible for ensuring that the stream is scheduled on a dispatch queue and that the queue is started. If there’s a problem scheduling the stream on the queue, an error will be returned when you try to start the stream. To start receiving events on the stream, call FSEventStreamStart(_:). To remove the stream from the queue on which it was scheduled, call FSEventStreamSetDispatchQueue(_:_:) with a NULL queue parameter or call FSEventStreamInvalidate(_:) which does the same thing. You must eventually call FSEventStreamInvalidate(_:) and it’s an error to call FSEventStreamInvalidate(_:) without having the stream either scheduled on a runloop or a dispatch queue, so don’t set the dispatch queue to NULL before calling FSEventStreamInvalidate(_:).