---
title: NSWillBecomeMultiThreaded
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/nsnotification/name-swift.struct/nswillbecomemultithreaded
---

# NSWillBecomeMultiThreaded

Posted when the first thread is detached from the current thread. The NSThread class posts this notification at most once—the first time a thread is detached using detachNewThreadSelector(_:toTarget:with:) or the start() method. Subsequent invocations of those methods do not post this notification. Observers of this notification have their notification method invoked in the main thread, not the new thread. The observer notification methods always execute before the new thread begins executing.

## Declaration

```swift
static let NSWillBecomeMultiThreaded: NSNotification.Name
```

## Discussion

Discussion This notification does not contain a notification object or a userInfo dictionary.

## See Also

### Notifications

- [NSDidBecomeSingleThreaded](foundation/nsnotification/name-swift.struct/nsdidbecomesinglethreaded.md)
- [NSThreadWillExit](foundation/nsnotification/name-swift.struct/nsthreadwillexit.md)