Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of boost. Click here for the latest Boost documentation.

Boost.Python

Header <boost/python/return_value_policy.hpp>

Contents

Introduction
Classes
Class Template return_value_policy
Class Template return_value_policy synopsis
Example

Introduction

return_value_policy instantiations are simply models of CallPolicies which are composed of a ResultConverterGenerator and optional Base CallPolicies.

Classes

Class template return_value_policy

return_value_policy template parameters
Parameter Requirements Default
ResultConverterGenerator A model of ResultConverterGenerator.
Base A model of CallPolicies default_call_policies

Class template return_value_policy synopsis

namespace boost { namespace python
{
  template <class ResultConverterGenerator, class Base = default_call_policies>
  struct return_value_policy : Base
  {
      typedef ResultConverterGenerator result_converter;
  };
}}

Example

C++ Module Definition

#include <boost/python/module.hpp>
#include <boost/python/class.hpp>
#include <boost/python/copy_const_reference.hpp>
#include <boost/python/return_value_policy.hpp>

// classes to wrap
struct Bar { int x; }

struct Foo {
   Foo(int x) : { b.x = x; }
   Bar const& get_bar() const { return b; }
 private:
   Bar b;
};

// Wrapper code
using namespace boost::python;
BOOST_PYTHON_MODULE(my_module)
{
   class_<Bar>("Bar");

   class_<Foo>("Foo", init<int>())
      .def("get_bar", &Foo::get_bar
          , return_value_policy<copy_const_reference>())
      ;
}

Python Code

>>> from my_module import *
>>> f = Foo(3)         # create a Foo object
>>> b = f.get_bar()    # make a copy of the internal Bar object

Revised 13 November, 2002

© Copyright Dave Abrahams 2002.