Re: [pygccxml-development] Cannot exclude inherited virtual methods

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

On Thu, Feb 19, 2009 at 4:17 PM, Patrick Hartling
<pat...@pr...> wrote:
> Roman Yakovenko wrote:
>>
>> On Thu, Feb 19, 2009 at 1:57 AM, Patrick Hartling
>> <pat...@pr...> wrote:
>>>
>>> I have a case where a base class defines virtual methods that are
>>> inherited
>>> by a derived class. I need to be able to exclude at least one of the
>>> virtual
>>> methods from the generated Boost.Python code for the derived class, but I
>>> cannot figure out how to do it. If I understand correctly, I am having
>>> problems because the virtual methods are not overridden by the derived
>>> class, and thus they are not part of the
>>> pyplusplus.decl_wrappers.class_wrapper.class_t object for the derived
>>> class.
>>>
>>> I have attached a header file and Py++ script that demonstrate the issue.
>>> Is
>>> there some way for me to apply a customization to the class wrapper's
>>> inherited virtual methods for the derived object? I am using r1669 of the
>>> pygccxml trunk and GCC 0.9 (1.127).
>>
>> I am not sure, I understand you correctly. The following is the code
>> generated by Py++.
>>
>> Please change it so I could understand what you want.
>
> What I would like to see is the following generated by Py++:
>
> #include "boost/python.hpp"
>
> namespace bp = boost::python;
>
> struct Base_wrapper : Base, bp::wrapper< Base > {
>
>    Base_wrapper(Base const & arg )
>    : Base( arg )
>      , bp::wrapper< Base >(){
>        // copy constructor
>
>    }
>
>    Base_wrapper()
>    : Base()
>      , bp::wrapper< Base >(){
>        // null constructor
>
>    }
>
>    virtual void f( int v ) {
>        if( bp::override func_f = this->get_override( "f" ) )
>            func_f( v );
>        else
>            this->Base::f( v );
>    }
>
>
>    void default_f( int v ) {
>        Base::f( v );
>    }
>
>    virtual void f( float v ) {
>        if( bp::override func_f = this->get_override( "f" ) )
>            func_f( v );
>        else
>            this->Base::f( v );
>    }
>
>
>    void default_f( float v ) {
>        Base::f( v );
>    }
>
> };
>
> BOOST_PYTHON_MODULE(pyplusplus){
>    bp::class_< Base_wrapper >( "Base" )
>        .def(
>            "f"
>            , (void ( ::Base::* )( int ) )(&::Base::f)
>            , (void ( Base_wrapper::* )( int ) )(&Base_wrapper::default_f)
>            , ( bp::arg("v") ) )
>        .def(
>            "f"
>            , (void ( ::Base::* )( float ) )(&::Base::f)
>            , (void ( Base_wrapper::* )( float ) )(&Base_wrapper::default_f)
>            , ( bp::arg("v") ) );
>
>    bp::class_< Derived, bp::bases< Base > >( "Derived" )
>        .def(
>            "f"
>            , (void ( ::Base::* )( int ) )(&::Base::f)
>            , ( bp::arg("v") ) )
>        .def(
>            "f"
>            , (void ( ::Base::* )( float ) )(&::Base::f)
>            , ( bp::arg("v") ) );
> }
>
> I have three goals:
>
> 1. Expose Base in a manner that allows its virtual methods to be overridden
> by a Python subclass.

This is what you already have .

> 2. Expose Derived in a manner that *does not* allow its virtual methods to
> be overridden by a Python subclass.

Py++ doesn't allow to do this and it is not simple to achieve in
general use case. For example, if Base class has pure virtual method,
the wrapper should be generated.

> 3. Prevent the exposure of an inherited, non-overridden virtual method with
> a signature that does not work well with Python.

For this case, Py++ introduces "Function Transformation" feature,
which works fine for all public member functions, even pure virtual
http://language-binding.net/pyplusplus/documentation/functions/transformation/transformation.html?highlight=function%20transformation

> The third item was not expressed in my original message or in the code
> example because I wanted to focus on being able to exclude an inherited
> virtual method with no override. That seems to me to be the fundamental
> issue that I am seeing. I can exclude virtual methods for Base, but those
> that are inherited by Derived and not overridden seem beyond my reach for
> excluding.

There is no "clean" way to achieve this, but try to take a look on
http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/pyplusplus/decl_wrappers/class_wrapper.py?revision=1664&view=markup
redefined_funcs function.

It returns reference to list, which contains all function that should
be redefined in the class wrapper. Try to delete it content.

HTH

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