---
title: concurrent
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/nsenumerationoptions/concurrent
---

# concurrent

Specifies that the Block enumeration should be concurrent.

## Declaration

```swift
static var concurrent: NSEnumerationOptions { get }
```

## Discussion

Discussion The order of invocation is nondeterministic and undefined; this flag is a hint and may be ignored by the implementation under some circumstances; the code of the Block must be safe against concurrent invocation.

## See Also

### Constants

- [reverse](foundation/nsenumerationoptions/reverse.md)