---
title: "CFMessagePortSetInvalidationCallBack(_:_:)"
framework: corefoundation
role: symbol
role_heading: Function
path: "corefoundation/cfmessageportsetinvalidationcallback(_:_:)"
---

# CFMessagePortSetInvalidationCallBack(_:_:)

Sets the callback function invoked when a CFMessagePort object is invalidated.

## Declaration

```swift
func CFMessagePortSetInvalidationCallBack(_ ms: CFMessagePort!, _ callout: CFMessagePortInvalidationCallBack!)
```

## Parameters

- `ms`: The message port to examine.
- `callout`: The callback function to invoke when ms is invalidated. Pass NULL to remove a callback.

## Discussion

Discussion If ms is already invalid, callout is invoked immediately.

## See Also

### Configuring a CFMessagePort Object

- [CFMessagePortCreateRunLoopSource(_:_:_:)](corefoundation/cfmessageportcreaterunloopsource(_:_:_:).md)
- [CFMessagePortSetName(_:_:)](corefoundation/cfmessageportsetname(_:_:).md)