
:mod:`aepack` --- Conversion between Python variables and AppleEvent data containers
====================================================================================

.. module:: aepack
   :platform: Mac
   :synopsis: Conversion between Python variables and AppleEvent data containers.
.. sectionauthor:: Vincent Marchetti <vincem@en.com>


.. % \moduleauthor{Jack Jansen?}{email}

The :mod:`aepack` module defines functions for converting (packing) Python
variables to AppleEvent descriptors and back (unpacking). Within Python the
AppleEvent descriptor is handled by Python objects of built-in type
:class:`AEDesc`, defined in module :mod:`Carbon.AE`.

The :mod:`aepack` module defines the following functions:


.. function:: pack(x[, forcetype])

   Returns an :class:`AEDesc` object  containing a conversion of Python value x. If
   *forcetype* is provided it specifies the descriptor type of the result.
   Otherwise, a default mapping of Python types to Apple Event descriptor types is
   used, as follows:

   +-----------------+-----------------------------------+
   | Python type     | descriptor type                   |
   +=================+===================================+
   | :class:`FSSpec` | typeFSS                           |
   +-----------------+-----------------------------------+
   | :class:`FSRef`  | typeFSRef                         |
   +-----------------+-----------------------------------+
   | :class:`Alias`  | typeAlias                         |
   +-----------------+-----------------------------------+
   | integer         | typeLong (32 bit integer)         |
   +-----------------+-----------------------------------+
   | float           | typeFloat (64 bit floating point) |
   +-----------------+-----------------------------------+
   | string          | typeText                          |
   +-----------------+-----------------------------------+
   | unicode         | typeUnicodeText                   |
   +-----------------+-----------------------------------+
   | list            | typeAEList                        |
   +-----------------+-----------------------------------+
   | dictionary      | typeAERecord                      |
   +-----------------+-----------------------------------+
   | instance        | *see below*                       |
   +-----------------+-----------------------------------+

   If *x* is a Python instance then this function attempts to call an
   :meth:`__aepack__` method.  This method should return an :class:`AEDesc` object.

   If the conversion *x* is not defined above, this function returns the Python
   string representation of a value (the repr() function) encoded as a text
   descriptor.


.. function:: unpack(x[, formodulename])

   *x* must be an object of type :class:`AEDesc`. This function returns a Python
   object representation of the data in the Apple Event descriptor *x*. Simple
   AppleEvent data types (integer, text, float) are returned as their obvious
   Python counterparts. Apple Event lists are returned as Python lists, and the
   list elements are recursively unpacked.  Object references (ex. ``line 3 of
   document 1``) are returned as instances of :class:`aetypes.ObjectSpecifier`,
   unless ``formodulename`` is specified.  AppleEvent descriptors with descriptor
   type typeFSS are returned as :class:`FSSpec` objects.  AppleEvent record
   descriptors are returned as Python dictionaries, with 4-character string keys
   and elements recursively unpacked.

   The optional ``formodulename`` argument is used by the stub packages generated
   by :mod:`gensuitemodule`, and ensures that the OSA classes for object specifiers
   are looked up in the correct module. This ensures that if, say, the Finder
   returns an object specifier for a window you get an instance of
   ``Finder.Window`` and not a generic ``aetypes.Window``. The former knows about
   all the properties and elements a window has in the Finder, while the latter
   knows no such things.


.. seealso::

   Module :mod:`Carbon.AE`
      Built-in access to Apple Event Manager routines.

   Module :mod:`aetypes`
      Python definitions of codes for Apple Event descriptor types.

   `Inside Macintosh: Interapplication Communication <http://developer.apple.com/techpubs/mac/IAC/IAC-2.html>`_
      Information about inter-process communications on the Macintosh.

