“类型为"void(exeCallback :: *)(int)"的值"不能将其分配给类型为"void(*)(int)"的实体， [英] "a value of type "void (exeCallback::*)(int)" cannot be assigned to an entity of type "void (*)(int)""

问题描述

可能重复:
禁用不良功能转换"警告

我试图用我的脑袋围绕c ++函数指针.为了保持基本的学习经验，我创建了一个测试函数指针示例.最终，我想通过引用传递所有现成的实例化对象，以便我可以回调该对象的方法.但是，为了学习和理解，我想坚持使用c ++函数指针的基础知识.我仅使用.cpp文件创建了一个工作示例，但我未成功完成的部分是在.cpp和.h中使用了函数指针.使用.cpp和.h文件时，要使我的学习示例成功工作，我该怎么做?

I am attempting to wrap my brain around c++ function pointers. To keep my learning experience basic, I created a test function pointer example. Eventually, I would like to pass all-ready instantiated objects by reference so I can callback the object's method; however, for the sake of learning and understand, I would like to stick to the basics of c++ function pointers. I created a working example just using a .cpp file, but the part that I am not succeeding at is using function pointers in .cpp and .h. What am I not doing correctly to get my learning example to work successfully when using .cpp and .h files?

我创建了两个文件exeCallback.h和exeCallback.cpp.

I created two files, exeCallback.h and exeCallback.cpp.

.h文件

/*
File: exeCallback.h

Header file for exeCommand Library.
*/

#ifndef EXECALLBACK_H
#define EXECALLBACK_H

#include "mbed.h"

#include <map>

class exeCallback
{
public:
    exeCallback();

    void my_int_func(int x);

    void (*foo)(int);
private:
};

#endif

.cpp文件:

/*
File: exeCallback.cpp

Execute functions in other Sensor libraries/classes

Constructor
*/

#include "mbed.h"
#include "ConfigFile.h"
#include "msExtensions.h"
#include "cfExtensions.h"
#include "exeCallback.h"

exeCallback::exeCallback()
{

    foo = &exeCallback::my_int_func;

    /* call my_int_func (note that you do not need to write (*foo)(2) ) */
    foo( 2 );

}

void exeCallback::my_int_func(int x)
{
    printf( "%d\n", x );
}

推荐答案

该错误告诉您正在尝试将成员函数的指针分配给(非成员)函数的指针.有关差异的更多信息，请参见[here](错误告诉您正在尝试将成员函数的指针分配给(非成员)函数的指针.)看来您需要将 foo 声明为

The error is telling you that you are trying to assign a pointer to a member function to a pointer to a (non-member) function. See [here](The error is telling you that you are trying to assign a pointer to a member function to a pointer to a (non-member) function.) for more on the differences. It looks like you need to declare foo as

void (exeCallback::*foo)(int);

或者通过使用 std :: function 来使您的生活更轻松代码> (如果没有C ++ 11支持，则为 boost :: function ).

Or make your life easier by using std::function (or boost::function if you don't have C++11 support).

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