c++学习2011-02-27

背景：友元 前向声明

 

源代码：#include <iostream>using namespace std;

//class Car;

class Boat{private: float Weight; public: Boat(float weight = 0) {  Weight = weight; } friend float totalWeight(Boat &a,Car &b);};

class Car{private: float Weight;public: Car(float weight = 0) {  Weight = weight; } friend float totalWeight(Boat &a,Car &b); };

 

 

float totalWeight(Boat &a,Car &b){ float c; c = a.Weight + b.Weight; return c; }

 

int main(){ Boat aa(100.1); Car bb(200.2);  cout << totalWeight(aa,bb) << endl; return 0;}

 

错误提示：syntax error : identifier 'Car' //语法错误：标识符Car'Weight' : cannot access private member declared in class 'Boat' //不能在类Boat中公然的访问私有成员

错误分析：Boat类和Cat类互相引用

研究结果（知识扩展）：我在开始时没有加上前向声明class Car，所以导致错误。这个错误能在编译阶段查出来，是静态错误，语法错误。