Re: [pygccxml-development] How to manage wrapper classes?

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

On 3/27/06, Matthias Baas <ba...@ir...> wrote:
> Roman Yakovenko wrote:
> > First of all I think you should be able to create custom call policies.
> > Take a look on this link:
> > http://boost.org/libs/python/doc/v2/CallPolicies.html#CallPolicies-conc=
ept
> >
> > May be, this will be enough, I am not sure.
>
> Interesting idea. From reading the above page I couldn't say if it is
> possible or not. precall() and postcall() are supposed to manage Python
> tuples which might indicate that they cannot access the original
> arguments....? Well, anyway, I posted a message to the c++-sig list,
> let's see what the "experts" have to say about this.
>
> >> So how should that be accomplished?
> >
> > There are 2 other ways to solve this problem.
> > 1. Create small wrappers in Python. I do not know exactly how it should=
 be done.
> >     But, I feel that this is the right way to go. I hope some days
> > pyplusplus will have
> >     3'rd tree - Python code creators ( they will generate Python code )=
.
>
> I have also thought about that and I might even get away with this for
> the Maya SDK, but in general, I think the problem would be that those
> Python wrappers would only be active when the object was created on the
> Python side and not on the C++ side.
>
> > 2. Create small wrapper in C++, in the way you did it. Just put that de=
claration
> >     in some namespace and add it to using add_code functions.
>
> But as I don't want to create the wrappers manually, how could I add
> wrappers that I generate automatically to the generated source files
> (not the main file)?

You don't have to create them manually. pygccxml is your friend. You
can find those
functions and generate 2 files: header and source with wrappers for
them. You just build
your own small code generator.

> > Using this
> >     approach you should be carefull. There are so many cases, while exp=
orting
> >     some function to Python. By the way, do we talk about pure virtual
> > functions or overloaded ones?
>
> What do you mean? The functions are not pure virtual, they are already
> implemented in the Maya SDK and I only need to access them. They are
> neither overloaded.... maybe I didn't understand the actual question...?

If you would deal with pure virtual or overloaded function the
solution would be much
complex.

> >> (and how can it be guaranteed that
> >> the user's wrapper code doesn't interfere with the wrapper code that
> >> might already get generated by pyplusplus?)
> >
> > 1. Do you still want to expose functions that returns, take by
> > reference MStatus object?
>
> Uhm, yes? (that's what my mail was about...?)

Sorry, I meant whether you want to expose original functions and
wrappers, or you want to
expose only wrappers?

> > If the answer is not then we can add replace_code function to decl_wrap=
per_t
> > class. Then pyplusplus will generate that code.
>
> What code would replace_code() replace?

pyplusplus generates code from declaration, right. We could add next
feature: instead
of creating code from declaration it will generate code provided by user.
Example: instead of doing next steps

my_class =3D mb.class_( 'X' )
mstatus_funcs =3D my_class.member_functions( all functions that has MStatus=
 )
for func in mstatus_funcs:
    func.exclude()
    my_class.add_code( wrapper function reference )

You would write something like:

my_class =3D mb.class_( 'X' )
mstatus_funcs =3D my_class.member_functions( all functions that has MStatus=
 )
for func in mstatus_funcs:
    func.replace_code( wrapper function reference )

This approach has few advances over first one.

I hope now I was clear.



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