C++ Boost


Header <boost/python/to_python_indirect.hpp>


Class Template to_python_indirect
Class Template to_python_indirect synopsis
Class Template to_python_indirect observer functions
Class Template to_python_indirect static functions


<boost/python/to_python_indirect.hpp> supplies a way to construct new Python objects that hold wrapped C++ class instances via a pointer or smart pointer.


Class template to_python_indirect

Class template to_python_indirect converts objects of its first argument type to python as extension class instances, using the ownership policy provided by its 2nd argument.

to_python_indirect Requirements
In the table below, x denotes an object of type T, h denotes an object of type boost::python::objects::instance_holder*, and p denotes an object of type U*.
Parameter Requirements Description
T Either U cv& (where cv is any optional cv-qualification) or a Dereferenceable type such that *x is convertible to U const&, where U is a class type. A type deferencing a C++ class exposed to Python using class template class_.
MakeHolder h = MakeHolder::execute(p); A class whose static execute() creates an instance_holder.
Instantiations of to_python_indirect are models of ResultConverter.

Class template to_python_indirect synopsis

namespace boost { namespace python
  template <class T, class MakeHolder>
  struct to_python_indirect
     static bool convertible();
     PyObject* operator()(T ptr_or_reference) const;
     static PyTypeObject* type();

Class template to_python_indirect observers

PyObject* operator()(T x) const;
Requires: x refers to an object (if it is a pointer type, it is non-null). convertible() == true.
Effects: Creates an appropriately-typed Boost.Python extension class instance, uses MakeHolder to create an instance_holder from x, installs the instance_holder in the new extension class instance, and returns a pointer to it.

Class template to_python_indirect statics

bool convertible();
Effects: Returns true iff any module has registered a Python type corresponding to U.


This example replicates the functionality of reference_existing_object, but without some of the compile-time error checking.

struct make_reference_holder
   typedef boost::python::objects::instance_holder* result_type;
   template <class T>
   static result_type execute(T* p)
      return new boost::python::objects::pointer_holder<T*, T>(p);

struct reference_existing_object
   // metafunction returning the ResultConverter
   template <class T>
   struct apply
      typedef boost::python::to_python_indirect<T,make_reference_holder> type;

Revised 13 November, 2002

© Copyright Dave Abrahams 2002. 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)