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- [section boost/python/make_function.hpp]
- [section Introduction]
- make_function() and make_constructor() are the functions used internally by def() and class_<>::def() to produce Python callable objects which wrap C++ functions and member functions.
- [endsect]
- [section Functions]
- ``
- template <class F>
- object make_function(F f)
- template <class F, class Policies>
- object make_function(F f, Policies const& policies)
- template <class F, class Policies, class KeywordsOrSignature>
- object make_function(F f, Policies const& policies, KeywordsOrSignature const& ks)
- template <class F, class Policies, class Keywords, class Signature>
- object make_function(F f, Policies const& policies, Keywords const& kw, Signature const& sig)
- ``
- [variablelist
- [[Requires][F is a function pointer or member function pointer type. If policies are supplied, it must be a model of CallPolicies. If kewords are supplied, it must be the result of a keyword-expression specifying no more arguments than the arity of f.]]
- [[Effects][Creates a Python callable object which, when called from Python, converts its arguments to C++ and calls f. If F is a pointer-to-member-function type, the target object of the function call (*this) will be taken from the first Python argument, and subsequent Python arguments will be used as the arguments to f.
- * If policies are supplied, it will be applied to the function as described here.
- * If keywords are supplied, the keywords will be applied in order to the final arguments of the resulting function.
- * If Signature is supplied, it should be an instance of an MPL front-extensible sequence representing the function's return type followed by its argument types. Pass a Signature when wrapping function object types whose signatures can't be deduced, or when you wish to override the types which will be passed to the wrapped function. ]]
- [[Returns][An instance of object which holds the new Python callable object.]]
- [[Caveats][An argument of pointer type may be 0 if None is passed from Python. An argument type which is a constant reference may refer to a temporary which was created from the Python object for just the duration of the call to the wrapped function, for example a std::vector conjured up by the conversion process from a Python list. Use a non-const reference argument when a persistent lvalue is required. ]]
- ]
- ``
- template <class F>
- object make_constructor(F f)
- template <class F, class Policies>
- object make_constructor(F f, Policies const& policies)
- template <class F, class Policies, class KeywordsOrSignature>
- object make_constructor(F f, Policies const& policies, KeywordsOrSignature const& ks)
- template <class F, class Policies, class Keywords, class Signature>
- object make_constructor(F f, Policies const& policies, Keywords const& kw, Signature const& sig)
- ``
- [variablelist
- [[Requires][F is a function pointer type. If policies are supplied, it must be a model of CallPolicies. If kewords are supplied, it must be the result of a keyword-expression specifying no more arguments than the arity of f.]]
- [[Effects][Creates a Python callable object which, when called from Python, converts its arguments to C++ and calls f.]]
- [[Returns][An instance of object which holds the new Python callable object.]]
- ]
- [endsect]
- [section Example]
- C++ function exposed below returns a callable object wrapping one of two functions.
- ``
- #include <boost/python/make_function.hpp>
- #include <boost/python/module.hpp>
- char const* foo() { return "foo"; }
- char const* bar() { return "bar"; }
- using namespace boost::python;
- object choose_function(bool selector)
- {
- if (selector)
- return boost::python::make_function(foo);
- else
- return boost::python::make_function(bar);
- }
- BOOST_PYTHON_MODULE(make_function_test)
- {
- def("choose_function", choose_function);
- }
- ``
- It can be used this way in Python:
- ``
- >>> from make_function_test import *
- >>> f = choose_function(1)
- >>> g = choose_function(0)
- >>> f()
- 'foo'
- >>> g()
- 'bar'
- ``
- [endsect]
- [endsect]
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