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- [section boost/python/to_python_indirect.hpp]
- [section Introduction]
- <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.
- [endsect]
- [section Class `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.
- [table
- [[Parameter][Requirements][Description]]
- [[T][Either `U cv&` (where cv is any optional cv-qualification) or a [link concepts.dereferenceable 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 [link high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel `class_`]. ]]
- [[MakeHolder][`h = MakeHolder::execute(p);` ][A class whose static `execute()` creates an `instance_holder`. ]]
- ]
- Instantiations of to_python_indirect are models of [link concepts.resultconverter `ResultConverter`].
- ``
- namespace boost { namespace python
- {
- template <class T, class MakeHolder>
- struct to_python_indirect
- {
- static bool convertible();
- PyObject* operator()(T ptr_or_reference) const;
- private:
- static PyTypeObject* type();
- };
- }}
- ``
- [endsect]
- [section Class `to_python_indirect` observers]
- ``PyObject* operator()(T x) const;``
- [variablelist
- [[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.]]
- ]
- [endsect]
- [section Class `to_python_indirect` statics]
- ``bool convertible()``
- [variablelist
- [[Effects][Returns true iff any module has registered a Python type corresponding to U. ]]
- ]
- [endsect]
- [endsect]
- [section Example]
- This example replicates the functionality of [link function_invocation_and_creation.models_of_resultconvertergenerat.boost_python_reference_existing_.class_reference_existing_object `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;
- };
- };
- ``
- [endsect]
- [endsect]
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