bump version to 12.2.2-pve1

[ceph.git] / ceph / src / boost / libs / python / doc / reference / return_value_policy.qbk

[section boost/python/return_value_policy.hpp]
[section Introduction]
return_value_policy instantiations are simply models of [link concepts.callpolicies `CallPolicies`] which are composed of a [link concepts.resultconverter.resultconvertergenerator_concept `ResultConverterGenerator`] and optional `Base` [link concepts.callpolicies `CallPolicies`]. 
[endsect]
[section Class template `return_value_policy`]
[table
[[Parameter][Requirements][Default]]
 [[ResultConverterGenerator][A model of [link concepts.resultconverter.resultconvertergenerator_concept `ResultConverterGenerator`]][]]
[[Base][A model of [link concepts.callpolicies `CallPolicies`]][default_call_policies]]
 ]
``
namespace boost { namespace python
{
  template <class ResultConverterGenerator, class Base = default_call_policies>
  struct return_value_policy : Base
  {
      typedef ResultConverterGenerator result_converter;
  };
}}
``
[endsect]
[section 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
``
[endsect]
[endsect]