add foo.bar.value to a module

Author: aoloe

scripter-class-in-class/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.4)
+project(scripting VERSION 1.0 LANGUAGES CXX)
+
+set(PYBIND11_PYTHON_VERSION 3.4)
+
+find_package(pybind11 CONFIG)
+
+add_executable(scripting
+    src/main.cpp
+    src/scripter.cpp
+)
+target_link_libraries(scripting
+    pybind11::embed
+)
+
+pybind11_add_module(fooapi
+    src/bar.cpp
+    src/foo.cpp
+)

scripter-class-in-class/README.md

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+# adding multiple classes to a python module
+
+the python code can set `foo.bar.value`
+
+~~~.sh
+$ mkdir build
+$ cmake -Dpybind11_DIR=/home/ale/bin/pybind11/share/cmake/pybind11 ..
+$ make
+$ ./scripting
+~~~

scripter-class-in-class/python/set-bar.py

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+import fooapi
+
+print(foo.bar.value)
+bar = foo.bar
+bar.value = 5

scripter-class-in-class/src/bar.cpp

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+#include <pybind11/pybind11.h>
+#include "bar.h"
+
+namespace py = pybind11;
+
+PYBIND11_MODULE(barapi, m) {
+    py::class_<Bar>(m, "Bar")
+        .def(py::init<>())
+        .def_readwrite("value", &Bar::value)
+        ;
+}
+

scripter-class-in-class/src/bar.h

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+#ifndef BAR_H
+#define BAR_H
+#include <iostream>
+struct Bar {
+    int value = 1;
+
+    Bar() {std::cout << "Making a bar!" << std::endl;}
+    Bar(const Bar& a) {value = a.value; std::cout << "Copying a new bar" << std::endl;}
+    ~Bar() {std::cout << "Bye-bye bar!" << std::endl;}
+};
+#endif

scripter-class-in-class/src/foo.cpp

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+#include <pybind11/pybind11.h>
+#include "foo.h"
+
+namespace py = pybind11;
+
+PYBIND11_MODULE(fooapi, m) {
+    py::class_<Bar>(m, "Bar")
+        .def(py::init<>())
+        .def_readwrite("value", &Bar::value)
+        ;
+    py::class_<Foo>(m, "Foo")
+        .def(py::init<>())
+        .def_readwrite("bar", &Foo::bar)
+        ;
+}

scripter-class-in-class/src/foo.h

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+#ifndef FOO_H
+#define FOO_H
+#include <iostream>
+#include "bar.h"
+struct Foo {
+    Bar bar{};
+
+    Foo() {std::cout << "Making a foo!" << std::endl;}
+    Foo(const Foo& a) {bar = a.bar; std::cout << "Copying a new foo" << std::endl;}
+    ~Foo() {std::cout << "Bye-bye foo!" << std::endl;}
+};
+#endif

scripter-class-in-class/src/main.cpp

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+#include <iostream>
+#include <pybind11/pybind11.h>
+#include <pybind11/embed.h>
+
+#include "scripter.h"
+
+int main() {
+    Scripter scripter;
+    scripter.runFile("../python/set-bar.py");
+}
+

scripter-class-in-class/src/scripter.cpp

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+#include "scripter.h"
+#include "foo.h"
+#include "bar.h"
+
+using namespace pybind11::literals; // for the ""_a
+
+void Scripter::runFile(std::string fileName)
+{
+	Foo foo;
+
+    std::cout << foo.bar.value << std::endl;
+
+	auto module = py::module::import("fooapi");
+
+    // auto locals = py::dict("foo"_a=foo); // foo by value
+	auto locals = py::dict("foo"_a=py::cast(foo, py::return_value_policy::reference)); // foo by reference
+
+    py::eval_file(fileName, py::globals(), locals);
+
+    std::cout << foo.bar.value << std::endl;
+}

scripter-class-in-class/src/scripter.h

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+#ifndef SCRIPTER_H
+#define SCRIPTER_H
+#include <string>
+
+#include <pybind11/pybind11.h>
+#include <pybind11/embed.h>
+
+namespace py = pybind11;
+
+class Scripter
+{
+    public:
+        void runFile(std::string fileName);
+    private:
+        py::scoped_interpreter guard{};
+};
+#endif