SWIG 将参数传递给 python 回调函数 [英] SWIG passing argument to python callback function

问题描述

所以我快完成了.现在我有调用 python 回调函数的工作代码.

So I'm almost done. Now I have working code which calls python callback function.

我现在唯一需要的是如何将参数传递给 python 回调函数.

Only thing I need now is how to pass argument to the python callback function.

我的 callback.c 是:

My callback.c is:

#include <stdio.h>

typedef void (*CALLBACK)(void);
CALLBACK my_callback = 0;

void set_callback(CALLBACK c);
void test(void);

void set_callback(CALLBACK c) {
  my_callback = c;
}

void test(void) {
  printf("Testing the callback function
");
  if (my_callback) (*my_callback)();
  else printf("No callback registered
");
}

我的 callback.i 是:

My callback.i is:

// An entirely different mechanism for handling a callback

%module callback
%{
typedef void (*CALLBACK)(void);
extern CALLBACK my_callback;

extern void set_callback(CALLBACK c);
extern void my_set_callback(PyObject *PyFunc);

extern void test(void);
%}

extern CALLBACK my_callback;

extern void set_callback(CALLBACK c);
extern void my_set_callback(PyObject *PyFunc);

extern void test(void);

%{
static PyObject *my_pycallback = NULL;
static void PythonCallBack(void)
{
   PyObject *func, *arglist;
   PyObject *result;

   func = my_pycallback;     /* This is the function .... */
   arglist = Py_BuildValue("()");  /* No arguments needed */
   result =  PyEval_CallObject(func, arglist);
   Py_DECREF(arglist);
   Py_XDECREF(result);
   return /*void*/;
}

void my_set_callback(PyObject *PyFunc)
{
    Py_XDECREF(my_pycallback);          /* Dispose of previous callback */
    Py_XINCREF(PyFunc);         /* Add a reference to new callback */
    my_pycallback = PyFunc;         /* Remember new callback */
    set_callback(PythonCallBack);
}

%}

%typemap(python, in) PyObject *PyFunc {
  if (!PyCallable_Check($input)) {
      PyErr_SetString(PyExc_TypeError, "Need a callable object!");
      return NULL;
  }
  $1 = $input;
}

效果很好.我应该怎么做才能将参数传递给 my_callback?任何帮助将不胜感激！

It works well. What should I do so I can pass argument to my_callback? Any help will be greatly appreciated!

推荐答案

回调的参数是 PyEval_CallObject() 的第二个参数.现在您正在构建一个空元组，这意味着没有参数".所以，改变它.你现在做什么:

The arguments to the callback are the second argument to PyEval_CallObject(). Right now you're building an empty tuple, which means "no arguments". So, change that. Where you now do:

arglist = Py_BuildValue("()");  /* No arguments needed */

您改为传递 Py_BuildValue 您希望 Python 函数接收的任何参数.例如，如果你想向回调传递一个整数、一个字符串和一个你从某个地方得到的 Python 对象，你可以这样做:

you instead pass Py_BuildValue whatever arguments you want the Python function to receive. For example, if you want to pass the callback an integer, a string and a Python object you got from somewhere, you would do:

arglist = Py_BuildValue("(isO)", the_int, the_str, the_pyobject);

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