朋友功能我怎样才能在全球范围内改变他们的成员

Question

我如何才能全局更改友元函数的成员，而不仅仅是在其块内？我在下面有一个简单的例子：

预期输出（整数）： 45 35 35

#include<iostream>
using namespace std;

class dog
{
    private:
        int HealthPoints;
        int Damage;
    public:
    dog(int HealthPoints, int Damage){
        this->HealthPoints = HealthPoints;
        this->Damage = Damage;
    }
    friend void doAttack(dog,dog);
    int getHealthPoints(){return HealthPoints;}
    int getDamage(){return Damage;}
};

void doAttack(dog Attacker, dog Attacked){
    Attacked.HealthPoints = Attacked.HealthPoints - Attacker.Damage;
    cout << Attacked.HealthPoints << "\tvalue inside friend function" << endl;
}

int main()
{
    dog a(45, 10);
    dog b(45, 10);
    cout << b.getHealthPoints() << "\tvalue before friend function" << endl;
    doAttack(a, b);
    cout << b.getHealthPoints() << "\tvalue after friend function";
    return 0;
}

Answer 1

您不需要全局变量。您目前正在做的是按值传递 Attacker 和 Attacked - 例如复制它们。您在 doAttack 中对这些副本进行了更改。原件永远不会被修改。而是通过引用传递它们。

我也更改了您的函数的名称，以便更友好。随时将其改回。

void doPet(dog& Petter, dog& Petted) {
    Petted.LovePoints = Petted.LovePoints + Petter.Friendliness;
    cout << Petted.LovePoints << "\tvalue inside friend function" << endl;
}

朋友功能我怎样才能在全球范围内改变他们的成员

Friend function how can i change their members globally

c++

class

global-variables

friend-function