[PyQt] SIP: deriving a python class from a C++ ABC results in a TypeError exception

[Demetrius Cassidy]

Actually I made a small mistake, OpalLocalEndPoint has a GetMediaFormats
implementation, but the issue remains.

class OpalLocalEndPoint : OpalEndPoint
{
  virtual OpalMediaFormatList GetMediaFormats() const;
};

On Sat, Jul 2, 2011 at 5:39 PM, Demetrius Cassidy <dcassidy36 at gmail.com>wrote:

> I have a C++ class which is declared with pure virtual methods, but if I
> derive from this class in python and implement the pure virtual methods, I
> get an exception:
> TypeError: pyvoip.opal.OpalPCSSEndPoint cannot be instantiated or
> sub-classed
>
> My python class is declared as following:
>
> class PCSSEndPoint(OpalPCSSEndPoint):
>   def __init__(self):
>   super(OpalPCSSEndPoint, self).__init__()
>
> def OnShowIncoming(self, connection):
> return True
>
> def OnShowOutgoing(self, connection):
> return True
>
> def GetMediaFormats(self):
>   return []
>
>
> SIP definitions:
>
> class OpalPCSSEndPoint : OpalLocalEndPoint /Abstract/
> {
>
> /**Call back to indicate that remote is ringing.
> If false is returned the call is aborted.
>
> The default implementation is pure.
> */
> virtual PBoolean OnShowIncoming(
> const OpalPCSSConnection & connection /NoCopy/ ///< Connection having event
> ) = 0;
>
> /**Call back to indicate that remote is ringing.
> If false is returned the call is aborted.
>
> The default implementation is pure.
> */
> virtual PBoolean OnShowOutgoing(
> const OpalPCSSConnection & connection /NoCopy/ ///< Connection having event
> ) = 0;
>
> };
>
> Now the base class of OpalPCSSEndPoint is also an ABC, as it derives from
> an ABC but does not re-define the pure virtual function:
>
> class OpalLocalEndPoint : OpalEndPoint /Abstract/
> {
>   ...
> };
>
> class OpalEndPoint /Abstract/
> {
> virtual OpalMediaFormatList GetMediaFormats() const = 0;
> };
>
> I tried removing  /Abstract/ from OpalLocalEndPoint, but it made no
> difference.  Any idea what's wrong in this scenario? The only way this
> works, is if I subclass OpalPCSSEndPoint in C++ and then in Python create a
> class derived from my OpalPCSSEndPoint subclass.
>
>
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