---
title: didBecomeActive
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/notificationcenter/messageidentifier/didbecomeactive-79dvm
---

# didBecomeActive

An identifier for a message about a host app moving from the inactive to the active state.

## Declaration

```swift
static var didBecomeActive: NotificationCenter.BaseMessageIdentifier<NSExtensionContext.DidBecomeActiveMessage> { get }
```

## Discussion

Discussion Use this identifier with NotificationCenter’s addObserver(of:for:using:) or messages(of:for:bufferSize:) methods to observe messages of type NSExtensionContext.DidBecomeActiveMessage.

## See Also

### Identifying extension messages

- [willResignActive](foundation/notificationcenter/messageidentifier/willresignactive-9z4xc.md)
- [didEnterBackground](foundation/notificationcenter/messageidentifier/didenterbackground-5gdtk.md)
- [willEnterForeground](foundation/notificationcenter/messageidentifier/willenterforeground-p1og.md)