C++使用回调函数

在类的非静态成员函数中访问类的非静态成员的时候，编译器会自动将对象本身的地址作为一个隐含参数传递给函数，即"this"指针。
class CTest
{
    public:
        int m_test();
};
CTest test;
test.m_test() //会被编译成 test.m_test(CTest *this);

处理方法：1.使用纯c语言的函数，然后把该函数作为一个类的友元函数；
                  2.把类的一个成员函数定义成静态函数，然后把静态函数作为回调函数传递；
例1：
#include <iostream>
using namespace std;
class CCallback
{
        public:
                CCallback(int i):m_data(i){
        // m_this = this;
                }
                ~CCallback(){}
                static void callback(CCallback *data){
                        cout << "callback function start..." << endl;
                        cout << data->m_data << endl;
                }
                int m_data;
        private:
                static CCallback * s_this;
};

CCallback * CCallback::s_this = NULL;
void f(void (*p)(CCallback *), CCallback * data)
{
        p(data);
}

int main(int argc, char **argv)
{
        CCallback * example_one = new CCallback(10);
        CCallback * example_two = new CCallback(12);
        void (*p)(CCallback *);
        p = CCallback::callback;
        f(p, example_one);
        f(p, example_two);
        return 0;
}
Note:上面的例子虽然是使用静态函数，但是可以使用多个实例而互不干扰，下面这个例子只能有一个实例；

例2：
#include <iostream>
using namespace std;
class CCallback
{
        public:
                CCallback(int i):m_data(i){
                        s_this = this;
                }
                ~CCallback(){}
                static void callback(){
                        cout << "callback function start..." << endl;
                        cout << s_this->m_data << endl;
                }
                int m_data;
        private:
                static CCallback * s_this;
};

CCallback * CCallback::s_this = NULL;
void f(void (*p)())
{
        p();
}

int main(int argc, char **argv)
{
        CCallback * example = new CCallback(10);
        void (*p)();
        p = CCallback::callback;
        f(p);
        return 0;
}
Note:例2只能够对拥有callback的类创造一个实例，如果想控制只创建一个实例，可以使用singleton pattern.