---
title: didBecomeInvalid
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/notificationcenter/messageidentifier/didbecomeinvalid
---

# didBecomeInvalid

An identifier for a message about a port becoming invalid.

## Declaration

```swift
static var didBecomeInvalid: NotificationCenter.BaseMessageIdentifier<Port.DidBecomeInvalidMessage> { get }
```

## Discussion

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