c++个人练习

（1）前置声明的练习

头文件

#ifndef FRONT_H
#define FRONT_H
#include <iostream>

using namespace std;


class B;             // 这是前置声明(Forward declaration)


class A
{
private:

         B* b;

public:
         A(B* b);

         void someMethod();
};


class B

{

private:

public:

         void someMethod();

};
#endif // FRONT_H

函数的实现，两个类互相调用必须如此。

#include "front.h"

A::A(B* b):b(b)
{

}

void A::someMethod()
{
         b->someMethod();
}

void B::someMethod()
{
         cout << "something happened..." << endl;
}

主函数

#include "front.h"

int main(int argc, char** argv)
{
         B* b = new B();
         A* a = new A(b);

         a->someMethod();

         delete a;
         delete b;

         return 0;
}

结果输出“something happened”