66 lines
2.7 KiB
Plaintext
66 lines
2.7 KiB
Plaintext
[section boost/python/to_python_indirect.hpp]
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[section Introduction]
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<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.
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[endsect]
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[section Class `to_python_indirect`]
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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.
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[table
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[[Parameter][Requirements][Description]]
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[[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_`]. ]]
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[[MakeHolder][`h = MakeHolder::execute(p);` ][A class whose static `execute()` creates an `instance_holder`. ]]
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]
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Instantiations of to_python_indirect are models of [link concepts.resultconverter `ResultConverter`].
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``
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namespace boost { namespace python
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{
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template <class T, class MakeHolder>
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struct to_python_indirect
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{
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static bool convertible();
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PyObject* operator()(T ptr_or_reference) const;
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private:
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static PyTypeObject* type();
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};
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}}
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``
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[endsect]
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[section Class `to_python_indirect` observers]
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``PyObject* operator()(T x) const;``
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[variablelist
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[[Requires][`x` refers to an object (if it is a pointer type, it is non-null). `convertible() == true`.]]
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[[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.]]
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]
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[endsect]
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[section Class `to_python_indirect` statics]
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``bool convertible()``
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[variablelist
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[[Effects][Returns true iff any module has registered a Python type corresponding to U. ]]
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]
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[endsect]
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[endsect]
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[section Example]
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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.
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``
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struct make_reference_holder
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{
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typedef boost::python::objects::instance_holder* result_type;
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template <class T>
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static result_type execute(T* p)
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{
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return new boost::python::objects::pointer_holder<T*, T>(p);
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}
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};
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struct reference_existing_object
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{
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// metafunction returning the ResultConverter
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template <class T>
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struct apply
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{
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typedef boost::python::to_python_indirect<T,make_reference_holder> type;
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};
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};
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``
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[endsect]
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[endsect]
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