## 15.15.1 AEServer Objects

`installaehandler` (classe, type, callback)
  Installs an AppleEvent handler. `Classe` and `type` are the four-char OSA Class and Type designators, `'****'` wildcards are allowed. When a matching AppleEvent is received the parameters are decoded and your callback is invoked.

`callback` (_object, **kwargs)
  Your callback is called with the OSA Direct Object as first positional parameter. The other parameters are passed as keyword arguments, with the 4-char designator as name. Three extra keyword parameters are passed: `_class` and `_type` are the Class and Type designators and `_attributes` is a dictionary with the AppleEvent attributes.

  The return value of your method is packed with `aetools.packevent` and sent as reply.

Note that there are some serious problems with the current design. AppleEvents which have non-identifier 4-char designators for arguments are not implementable, and it is not possible to return an error to the originator. This will be addressed in a future release.