cython - 包装一个 cpp 类聚合另一个

Question

我想用 Cython 为 cpp 类创建一个包装器。但是这个类聚合了另一个类，我不知道是否还需要为这个类创建一个包装器，因为我不想从 Python 调用第二个类。

有 cpp 类：

testclass.hpp

#ifndef TESTCLASS_H
#define TESTCLASS_H
#include "ocean.hpp"

class TestClass {
    private:
        Ocean _ocean;

    public:
        int x, y;
        TestClass();
        ~TestClass();
        int Multiply(int a, int b);
};
#endif

testclass.cpp

#include "testclass.hpp"
TestClass::TestClass()
{
    x = 5;
    y = 1;
    _ocean = Ocean();
}

TestClass::~TestClass()
{
    std::cout << "Calling destructor" << std::endl;
}

int TestClass::Multiply(int a, int b)
{
    return a*b;
}

海洋.hpp

#ifndef OCEAN_H
#define OCEAN_H
class Ocean {
    public:
        double _depth;
        double _rho;

        Ocean();
        virtual ~Ocean();
        void setwaterdepth(double d);
};
#endif

我只想包装测试类，这是我尝试过的：

海洋.pxd

cdef extern from "ocean.hpp":
cdef cppclass Ocean:
    Ocean()

test.pyx

from ocean cimport Ocean

cdef extern from "testclass.hpp":
    cdef cppclass TestClass:
        TestClass()
        int x
        int y
        int Multiply(int a, int b)

cdef class pyTestClass:
    cdef TestClass* thisptr # hold a C++ instance

    def __cinit__(self):
        self.thisptr = new TestClass()

    def __dealloc__(self):
        del self.thisptr

    def Multiply(self, a, b):
        return self.thisptr.Multiply(a, b)

setup.py

from distutils.core import setup, Extension
from Cython.Build import cythonize

ext = Extension("test",
                sources=["test.pyx", "testclass.cpp"],
                language="c++")

setup(name="test",
      ext_modules=cythonize(ext))

Q1) 这样做的方法是否正确？ （当我编译这个时，我得到以下错误，我不明白这个错误。）

C:\MinGW\bin\gcc.exe -mdll -O -Wall -IC:\Python27\include -IC:\Python27\PC -c testclass.cpp -o build\temp.win32-2.7\Release\testclass.o
writing build\temp.win32-2.7\Release\test.def
C:\MinGW\bin\g++.exe -shared -s build\temp.win32-2.7\Release\test.o build\temp.win32-2.7\Release\testclass.o build\temp.win32-2.7\Release\test.def -LC:\Python27\libs -LC:\Python27\PCbuild -LC:\Python27\PC\VS9.0 -lpython27 -lmsv
cr90 -o E:\00-Projets\InWave\Couplage\PYW\C++\test3\test.pyd
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0x97): undefined reference to `Ocean::~Ocean()'
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0xa3): undefined reference to `Ocean::~Ocean()'
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0xe4): undefined reference to `Ocean::Ocean()'
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0xfa): undefined reference to `Ocean::Ocean()'
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0x11a): undefined reference to `Ocean::~Ocean()'
build\temp.win32-2.7\Release\testclass.o:testclass.cpp:(.text+0x196): undefined reference to `Ocean::~Ocean()'
collect2.exe: error: ld returned 1 exit status
error: command 'C:\\MinGW\\bin\\g++.exe' failed with exit status 1

Answer 1

我终于成功了。

无需包装 Ocean 类，因此无需为其创建 .pxd 文件。 但在 setup.py 中，包含所有 .cpp 依赖项很重要。

正如之前的 cmets 所说，在头文件中添加包含保护也很重要。

所以这是一个工作代码（用python setup.py build_ext --inplace编译）

海洋.hpp

#ifndef OCEAN_H
#define OCEAN_H

class Ocean {
    public:
        double _depth;
        double _rho;

        Ocean();
        virtual ~Ocean();
        void setwaterdepth(double d);
};

#endif

testclass.hpp

#ifndef TESTCLASS_H
#define TESTCLASS_H
#include "ocean.hpp"

class TestClass {
    private:
        Ocean _ocean;

    public:
        int x, y;
        TestClass();
        virtual ~TestClass();
        int Multiply(int a, int b);
        void _set_x(int x);
};

#endif

testclass.cpp

#include <iostream>
#include "testclass.hpp"
#include "ocean.hpp"

TestClass::TestClass()
{
    x = 5;
    y = 1;
    _ocean = Ocean();
    std::cout << "Calling constructor" << std::endl;
}

TestClass::~TestClass()
{
    std::cout << "Calling destructor" << std::endl;
}

int TestClass::Multiply(int a, int b)
{
    return a*b;
}

void TestClass::_set_x(int new_x)
{
    x = new_x;
}

test.pyx

cdef extern from "testclass.hpp":
    cdef cppclass TestClass:
        TestClass()
        int x
        int y
        int Multiply(int a, int b)

cdef class pyTestClass:
    cdef TestClass* thisptr # hold a C++ instance

    def __cinit__(self):
        self.thisptr = new TestClass()

    def __dealloc__(self):
        del self.thisptr

    def Multiply(self, a, b):
        return self.thisptr.Multiply(a, b)

    property y:

        # Here we use a property to expose the public member
        # y of TestClass to Python

        def __get__(pyTestClass self):
            return self.thisptr.y

        def __set__(pyTestClass self, value):
            self.thisptr.y = <int> value

setup.py

from distutils.core import setup, Extension
from Cython.Build import cythonize

ext = Extension("test",
            sources=["test.pyx", "testclass.cpp", "ocean.cpp"],
            language="c++")

setup(name="test", ext_modules=cythonize(ext))

包装测试

import test as wrapper

T = wrapper.pyTestClass()
print T.Multiply(3, 5)
print T.y
T.y = 3
print T.y

输出

Calling ocean constructor
Calling ocean constructor
Calling ocean destructor
Calling constructor
15
1
3
Calling destructor
Calling ocean destructor