Wrappers

Suppose you have this function:

    std::vector<std::string> names();

But you don't want to to export std::vector<std::string>, you want this function to return a python list of strings. Boost.Python has excellent support for things like that:

    list names_wrapper()
    {
        list result;
        // call original function
        vector<string> v = names();
        // put all the strings inside the python list
        vector<string>::iterator it;
        for (it = v.begin(); it != v.end(); ++it){
            result.append(*it);    
        }
        return result;
    }
    
    BOOST_PYTHON_MODULE(test)
    {
        def("names", &names_wrapper);
    }

Nice heh? Pyste supports this mechanism too. You declare the names_wrapper function in a header named "test_wrappers.h" and in the interface file:

    Include("test_wrappers.h")
    names = Function("names", "test.h")
    set_wrapper(names, "names_wrapper")

You can optionally declare the function in the interface file itself:

    names_wrapper = Wrapper("names_wrapper",
    """
    list names_wrapper()
    {
        // code to call name() and convert the vector to a list...
    }
    """)
    names = Function("names", "test.h")
    set_wrapper(names, names_wrapper)

The same mechanism can be used with member functions too. Just remember that the first parameter of wrappers for member functions is a pointer to the class, as in:

    struct C
    {
        std::vector<std::string> names();
    }

    list names_wrapper(C* c)
    {
        // same as before, calling c->names() and converting result to a list 
    }

And then in the interface file:

    C = Class("C", "test.h")
    set_wrapper(C.names, "names_wrapper")
Even though Boost.Python accepts either a pointer or a reference to the class in wrappers for member functions as the first parameter, Pyste expects them to be a pointer. Doing otherwise will prevent your code to compile when you set a wrapper for a virtual member function.

Copyright © 2003 Bruno da Silva de Oliveira
Copyright © 2002-2003 Joel de Guzman

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)