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86d825f330
Sergey Lyskov pointed out that the trampoline mechanism used to override
virtual methods from within Python caused unnecessary overheads when
instantiating the original (i.e. non-extended) class.
This commit removes this inefficiency, but some syntax changes were
needed to achieve this. Projects using this features will need to make a
few changes:
In particular, the example below shows the old syntax to instantiate a
class with a trampoline:
class_<TrampolineClass>("MyClass")
.alias<MyClass>()
....
This is what should be used now:
class_<MyClass, std::unique_ptr<MyClass, TrampolineClass>("MyClass")
....
Importantly, the trampoline class is now specified as the *third*
argument to the class_ template, and the alias<..>() call is gone. The
second argument with the unique pointer is simply the default holder
type used by pybind11.
99 lines
3.0 KiB
C++
99 lines
3.0 KiB
C++
/*
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example/example12.cpp -- overriding virtual functions from Python
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Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
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All rights reserved. Use of this source code is governed by a
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BSD-style license that can be found in the LICENSE file.
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*/
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#include "example.h"
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#include <pybind11/functional.h>
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/* This is an example class that we'll want to be able to extend from Python */
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class Example12 {
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public:
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Example12(int state) : state(state) {
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cout << "Constructing Example12.." << endl;
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}
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~Example12() {
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cout << "Destructing Example12.." << endl;
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}
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virtual int run(int value) {
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std::cout << "Original implementation of Example12::run(state=" << state
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<< ", value=" << value << ")" << std::endl;
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return state + value;
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}
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virtual bool run_bool() = 0;
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virtual void pure_virtual() = 0;
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private:
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int state;
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};
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/* This is a wrapper class that must be generated */
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class PyExample12 : public Example12 {
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public:
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using Example12::Example12; /* Inherit constructors */
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virtual int run(int value) {
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/* Generate wrapping code that enables native function overloading */
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PYBIND11_OVERLOAD(
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int, /* Return type */
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Example12, /* Parent class */
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run, /* Name of function */
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value /* Argument(s) */
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);
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}
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virtual bool run_bool() {
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PYBIND11_OVERLOAD_PURE(
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bool, /* Return type */
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Example12, /* Parent class */
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run_bool, /* Name of function */
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/* This function has no arguments. The trailing comma
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in the previous line is needed for some compilers */
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);
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}
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virtual void pure_virtual() {
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PYBIND11_OVERLOAD_PURE(
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void, /* Return type */
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Example12, /* Parent class */
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pure_virtual, /* Name of function */
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/* This function has no arguments. The trailing comma
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in the previous line is needed for some compilers */
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);
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}
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};
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int runExample12(Example12 *ex, int value) {
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return ex->run(value);
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}
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bool runExample12Bool(Example12* ex) {
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return ex->run_bool();
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}
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void runExample12Virtual(Example12 *ex) {
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ex->pure_virtual();
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}
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void init_ex12(py::module &m) {
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/* Important: indicate the trampoline class PyExample12 using the third
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argument to py::class_. The second argument with the unique pointer
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is simply the default holder type used by pybind11. */
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py::class_<Example12, std::unique_ptr<Example12>, PyExample12>(m, "Example12")
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.def(py::init<int>())
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/* Reference original class in function definitions */
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.def("run", &Example12::run)
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.def("run_bool", &Example12::run_bool)
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.def("pure_virtual", &Example12::pure_virtual);
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m.def("runExample12", &runExample12);
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m.def("runExample12Bool", &runExample12Bool);
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m.def("runExample12Virtual", &runExample12Virtual);
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}
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