友元类的应用

友元类的应用"/>

友元类的应用

要求
人物

基类：class Lovers

子类：Boyfriend,Girlfriend
第三者：class Others

子类：（无）
故事是这样的

基类Lovers的name属性访问级别为protected，但将Others类设为友缘关系。
第三者Others类到自己拥有kiss方法，希望调用。此kiss方法传参为Boyfriend类型的的对象。

代码

#include<iostream>
#include<string>
//基类
class Lovers
{
public:Lovers(std::string lovers_name);//构造器
protected:std::string name;friend class Others;
};
//子类
class Boyfriend :public Lovers
{
public:Boyfriend(std::string name);
};
class Girlfriend :public Lovers
{
public:Girlfriend(std::string name);
};
//第三者
class Others
{
public:std::string name;Others(std::string name);//构造器void dosomething(Boyfriend duixiangname);
};
//基类构造器
Lovers::Lovers(std::string lovers_name)
{this->name = lovers_name;
}
//子类构造器
Boyfriend::Boyfriend(std::string name) :Lovers(name)
{this->name = name;
}
Girlfriend::Girlfriend(std::string name) : Lovers(name)
{this->name = name;
}
//第三者构造器
Others::Others(std::string name)
{this->name = name;
}
//子类方法（访问基类的private部分)
void Others::dosomething(Boyfriend duixiangname)//传入的是一个class对象
{std::cout << "I am kissing " << duixiangname.name << std::endl;
}
int main()
{Boyfriend person1("Tony");Girlfriend person2("Alice");Others person3("Uncle");person3.dosomething(person1);system("pause");
}

运行结果

第三者Others成功运用自己的kiss方法访问到了Lovers类的name成员

输出：

I am kissing Tony
请按任意键继续. . .

版本2

将29，51行的参数类型Boyfriend改成了Lovers，这样在60行的调用不受限制

#include<iostream>
#include<string>
//基类
class Lovers
{
public:Lovers(std::string lovers_name);//构造器
protected:std::string name;friend class Others;
};
//子类
class Boyfriend :public Lovers
{
public:Boyfriend(std::string name);
};
class Girlfriend :public Lovers
{
public:Girlfriend(std::string name);
};
//第三者
class Others
{
public:std::string name;Others(std::string name);//构造器void dosomething(Lovers duixiangname);
};
//基类构造器
Lovers::Lovers(std::string lovers_name)
{this->name = lovers_name;
}
//子类构造器
Boyfriend::Boyfriend(std::string name) :Lovers(name)
{this->name = name;
}
Girlfriend::Girlfriend(std::string name) : Lovers(name)
{this->name = name;
}
//第三者构造器
Others::Others(std::string name)
{this->name = name;
}
//子类方法（访问基类的private部分)
void Others::dosomething(Lovers duixiangname)//传入的是一个class对象
{std::cout << "I am kissing " << duixiangname.name << std::endl;
}
int main()
{Boyfriend person1("Tony");Girlfriend person2("Alice");Others person3("Uncle");person3.dosomething(person2);system("pause");
}

输出：

I am kissing Alice
请按任意键继续. . .