---
title: "AEInstallEventHandler(_:_:_:_:_:)"
framework: coreservices
role: symbol
role_heading: Function
path: coreservices/1448596-aeinstalleventhandler
---

# AEInstallEventHandler(_:_:_:_:_:)

Adds an entry for an event handler to an Apple event dispatch table.

## Declaration

```swift
func AEInstallEventHandler(_ theAEEventClass: AEEventClass, _ theAEEventID: AEEventID, _ handler: AEEventHandlerUPP!, _ handlerRefcon: SRefCon!, _ isSysHandler: Bool) -> OSErr
```

## Parameters

- `theAEEventClass`: The event class for the Apple event or events to dispatch to this event handler. The Discussion section describes interactions between this parameter and the theAEEventID parameter. See doc://com.apple.documentation/documentation/coreservices/aeeventclass.
- `theAEEventID`: The event ID for the Apple event or events to dispatch to this event handler. The Discussion section describes interactions between this parameter and the theAEEventClass parameter. See doc://com.apple.documentation/documentation/coreservices/aeeventid.
- `handler`: A universal procedure pointer to the Apple event handler function to install. See doc://com.apple.documentation/documentation/coreservices/aeeventhandlerupp.
- `handlerRefcon`: A reference constant. The Apple Event Manager passes this value to the handler each time it calls it. If your handler doesn’t require a reference constant, pass 0 for this parameter.
- `isSysHandler`: Specifies the Apple event dispatch table to add the handler to. Pass TRUE to add the handler to the system dispatch table or FALSE to add the handler to your application’s dispatch table. See Version Notes for related information.

## Return Value

Return Value A result code. See Result Codes.

## Discussion

Discussion The parameters theAEEventClass and theAEEventID specify the event class and event ID of the Apple events handled by the handler for this dispatch table entry. If there is already an entry in the specified dispatch table for the same event class and event ID, it is replaced. For these parameters, you must provide one of the following combinations: the event class and event ID of a single Apple event to dispatch to the handler (for example, an event class of kAECoreSuite and an event ID of kAEDelete so that a specific kind of delete event is dispatched to the handler)  the typeWildCard constant for theAEEventClass and an event ID for theAEEventID, which indicates that Apple events from all event classes whose event IDs match theAEEventID should be dispatched to the handler (for example, an event class of typeWildCard and an event ID of kAEDelete so that for all event classes, the delete event is dispatched to the handler)  an event class for theAEEventClass and the typeWildCard constant for theAEEventID, which indicates that all events from the specified event class should be dispatched to the handler (for example, an event class of kAECoreSuite and an event ID of typeWildCard so that all events for the core suite are dispatched to the handler)  the typeWildCard constant for both the theAEEventClass and theAEEventID parameters, which indicates that all Apple events should be dispatched to the handler If you use the typeWildCard constant for either the theAEEventClass or the theAEEventID parameter (or for both parameters), the corresponding handler must return the error errAEEventNotHandled if it does not handle a particular event. If an Apple event dispatch table contains one entry for an event class and a specific event ID, and also contains another entry that is identical except that it specifies a wildcard value for either the event class or the event ID, the Apple Event Manager dispatches the more specific entry. For example, if an Apple event dispatch table includes one entry that specifies the event class as kAECoreSuite and the event ID as kAEDelete, and another entry that specifies the event class as kAECoreSuite and the event ID as typeWildCard, the Apple Event Manager dispatches the Apple event handler associated with the entry that specifies the event ID as kAEDelete. In addition to the Apple event handler dispatch tables, applications can add entries to special handler dispatch tables, as described in Managing Special Handler Dispatch Tables.  Version-Notes Thread safe starting in OS X v10.2. Your application should not install a handler in a system dispatch table with the goal that the handler will get called when other applications receive events—this won’t work in macOS. For more information, see The System Dispatch Table in Apple Event Dispatching in Apple Events Programming Guide.

## See Also

### Managing Apple Event Dispatch Tables

- [AEGetEventHandler(_:_:_:_:_:)](coreservices/1445631-aegeteventhandler.md)
- [AERemoveEventHandler(_:_:_:_:)](coreservices/1445239-aeremoveeventhandler.md)