Re: [pygccxml-development] Parameter passing, ownership semantics

[Gustavo C. <gjc...@gm...>]

On 2/19/07, Roman Yakovenko <rom...@gm...> wrote:
>
> Hi. Unfortunately I reproduced the error and was not able to  fix it
> :-(((((.
> There is something I don't understand  and I think  this is  Boost.Pythonbug.
>
> I do made some progress.
>
> 1. When you derive Python class from a C++ one you have to define __init__
>
>     method, otherwise your code will not work:
>
> class MyEvent(EventImpl):
>     def __init__( self ):
>         EventImpl.__init__( self )
>
>     def Notify(self):
>         print "Notify!"
>
> 2. I did small research for you. Read this post:
>    http://aspn.activestate.com/ASPN/Mail/Message/cpp-sig/1331901
>    and take a look on Boost.Python unit tests:
>
> http://boost.cvs.sourceforge.net/boost/boost/libs/python/test/auto_ptr.cpp?view=markup
>
> http://boost.cvs.sourceforge.net/boost/boost/libs/python/test/auto_ptr.py?view=markup
>
> What I found is:
> The ownership is really transfered. You can check this using simple
> technique:
>         Add new function to EventImpl:
>           virtual std::string class_name() const { return "EventImpl"; }
>         Add free function:
>            std::string get_class_name( const std::auto_ptr<EventImpl>& e
> ){
>                if( e.get() ){
>                    return e->class_name();
>                }
>                else{
>                   return "no object";
>                }
>            }
>         You will get the answer "no object", after "Schedule" call.
> So, may be you don't have to delete the Python object.
>
> I will submit the bug to the Boost.Python mailing list, hope somebody will
> be able to help.


I found this wiki with a possible solution for the problem:

http://wiki.python.org/moin/boost.python/HowTo#head-927c9493ac51c81b3f2484e486d85567ff316c8a

Unfortunately the provided code, after adaptions to my case, didn't even
compile :-(

-- 
Gustavo J. A. M. Carneiro
"The universe is always one step beyond logic."