---
title: "AEStreamOpenEvent(_:)"
framework: coreservices
role: symbol
role_heading: Function
path: coreservices/1445366-aestreamopenevent
---

# AEStreamOpenEvent(_:)

Opens a stream for an existing Apple event.

## Declaration

```swift
func AEStreamOpenEvent(_ event: UnsafeMutablePointer<AppleEvent>!) -> AEStreamRef!
```

## Parameters

- `event`: An existing Apple event. See doc://com.apple.documentation/documentation/coreservices/appleevent.

## Return Value

Return Value An AEStreamRef for the Apple event or NULL if the stream data structures could not be allocated.

## Discussion

Discussion Use this function to open a stream and add parameters to an existing Apple event. This function copies any parameters already in the Apple event to the stream prior to returning the AEStreamRef. When you are done adding parameters, use AEStreamClose(_:_:) to save them to the Apple event and close the stream.  If there is not enough available storage to complete the operation, AEStreamOpenEvent returns NULL and leaves the Apple event unchanged.

## See Also

### Creating Apple Event Structures Using Streams

- [AEStreamClose(_:_:)](coreservices/1449821-aestreamclose.md)
- [AEStreamCloseDesc(_:)](coreservices/1449272-aestreamclosedesc.md)
- [AEStreamCloseList(_:)](coreservices/1448185-aestreamcloselist.md)
- [AEStreamCloseRecord(_:)](coreservices/1449522-aestreamcloserecord.md)
- [AEStreamCreateEvent(_:_:_:_:_:_:_:)](coreservices/1446562-aestreamcreateevent.md)
- [AEStreamOpen()](coreservices/1447732-aestreamopen.md)
- [AEStreamOpenDesc(_:_:)](coreservices/1446544-aestreamopendesc.md)
- [AEStreamOpenKeyDesc(_:_:_:)](coreservices/1442897-aestreamopenkeydesc.md)
- [AEStreamOpenList(_:)](coreservices/1448594-aestreamopenlist.md)
- [AEStreamOpenRecord(_:_:)](coreservices/1447141-aestreamopenrecord.md)
- [AEStreamOptionalParam(_:_:)](coreservices/1444481-aestreamoptionalparam.md)
- [AEStreamSetRecordType(_:_:)](coreservices/1447704-aestreamsetrecordtype.md)
- [AEStreamWriteAEDesc(_:_:)](coreservices/1448487-aestreamwriteaedesc.md)
- [AEStreamWriteData(_:_:_:)](coreservices/1442610-aestreamwritedata.md)
- [AEStreamWriteDesc(_:_:_:_:)](coreservices/1450387-aestreamwritedesc.md)
- [AEStreamWriteKey(_:_:)](coreservices/1448750-aestreamwritekey.md)
- [AEStreamWriteKeyDesc(_:_:_:_:_:)](coreservices/1442568-aestreamwritekeydesc.md)