Re: [pygccxml-development] Can held_type be an abstract class?

[Roman Y. <rom...@gm...>]

On 6/18/06, Roman Yakovenko <rom...@gm...> wrote:
> On 6/18/06, Lakin Wecker <lak...@gm...> wrote:
> > Hi,
> >
> > I've applied some code that Roman and I came up with to wrap and
> > appropriately use the Ogre::SharedPtr class.  In one case I'm setting
> > the held_type of Ogre::Resource to be Ogre::SharedPtr <Ogre::Resource>
> >  ..  However when I try to compile the generated code, I get the
> > following error.
> >
> > /home/lakin/code_personal/python-ogre/build/Resource.pypp.cpp:284:
> > instantiated from here
> > /usr/include/boost/python/object/pointer_holder.hpp:179: error: cannot
> > allocate an object of abstract type 'Ogre::Resource'
> > /home/lakin/.local//include/OGRE/OgreResource.h:68: note:   because
> > the following virtual functions are pure within 'Ogre::Resource':
> > /home/lakin/.local//include/OGRE/OgreResource.h:101: note:  virtual
> > void Ogre::Resource::loadImpl()
> > /home/lakin/.local//include/OGRE/OgreResource.h:105: note:  virtual
> > void Ogre::Resource::unloadImpl()
> > /home/lakin/.local//include/OGRE/OgreResource.h:107: note:  virtual
> > size_t Ogre::Resource::calculateSize() const
> > /usr/include/boost/python/object/pointer_holder.hpp: In constructor
> > 'boost::python::objects::pointer_holder<Pointer,
> > Value>::pointer_holder(PyObject*, A0, A1, A2, A3, A4, A5) [with A0 =
> > Ogre::ResourceManager*, A1 =
> > boost::python::objects::reference_to_value<const Ogre::String&>, A2 =
> > long unsigned int, A3 =
> > boost::python::objects::reference_to_value<const Ogre::String&>, A4 =
> > bool, A5 = Ogre::ManualResourceLoader*, Pointer =
> > Ogre::SharedPtr<Ogre::Resource>, Value = Ogre::Resource]':
> >
> > Anyone with ideas?

Yes, I took a look on the problem. Now I understand it. First of all
gcc is right
Resource_wrapper is abstract class: loadImpl, unloadImpl and calculateSize
were not defined. Why those functions were not defined - because they are
declared as protected and we excluded them:

ogre_ns.calldefs( ~access_type_matcher_t ('public')).exclude ()

There are few problems here:
1. In this case I would expect from pyplusplus to give a warning
2. User should decide whether he want to give a Python programmer to ability
    to create new resource type or not.
    if the answer is yes, then those functions should not be excluded
    if the answer is no, then you should say to pyplusplus to finalize
the class.
    Right now pyplusplus does not support this.
    See next link for more information about "finalize" functionality
          http://www.boost.org/libs/python/pyste/doc/renaming_and_excluding.html
So, the short advise to you is: comment that line.

Another comment for the Resource class: you did not set held_type. It should
be set to Ogre::SharedPtr< Ogre::Resource >.

Hope I was clear.

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/