[python-win32] CastTo interface from other library

[Pieter Aarnoutse]

In the win32com.client class CastTo method, it is assumed that the
target interface type exists in the same library as the object to be
casted. To work around that issue, I modified the method with an
optional argument stating the target interface's library, as follows:

def CastTo_mod(ob, target, typelib = None):
    """'Cast' a COM object to another interface"""
    mod = None
    if not typelib is None: # caller provided typelib of target
      mod = gencache.MakeModuleForTypelib(typelib.clsid, typelib.lcid,
int(typelib.major), int(typelib.minor))
      if not hasattr(mod, target):
        raise ValueError("The interface name '%s' does not appear in the " \
                         "assigned library %r" % (target, typelib.ver_desc))
    # todo - should support target being an IID
    elif hasattr(target, "index"): # string like
    # for now, we assume makepy for this to work.
    # ... <snip> ....
    mod = gencache.GetModuleForCLSID(target_clsid)
    if not mod is None:
      target_class = getattr(mod, target)
      # resolve coclass to interface
      target_class = getattr(target_class, "default_interface", target_class)
      return target_class(ob) # auto QI magic happens
    raise ValueError

after which I can cast to the type from some other library (targetlib) like

object = CastTo(object, 'targetinterfacename', targetlib)

where targetlib is a TypelibSpec taken from a search by name in the
list returned from selecttlb.EnumTlbs().

Any chance we can have some functionality like that in the release?

Thanks, Pieter