---
title: barrier
framework: dispatch
role: symbol
role_heading: Type Property
path: dispatch/dispatchworkitemflags/barrier
---

# barrier

Cause the work item to act as a barrier block when submitted to a concurrent queue.

## Declaration

```swift
static let barrier: DispatchWorkItemFlags
```

## Discussion

Discussion When submitted to a concurrent queue, a work item with this flag acts as a barrier. Work items submitted prior to the barrier execute to completion, at which point the barrier work item executes. Once the barrier work item finishes, the queue returns to scheduling work items that were submitted after the barrier.

## See Also

### Work Item Flags

- [assignCurrentContext](dispatch/dispatchworkitemflags/assigncurrentcontext.md)
- [detached](dispatch/dispatchworkitemflags/detached.md)
- [enforceQoS](dispatch/dispatchworkitemflags/enforceqos.md)
- [inheritQoS](dispatch/dispatchworkitemflags/inheritqos.md)
- [noQoS](dispatch/dispatchworkitemflags/noqos.md)