c++第六章-（友元）

1.友元（激情四射的机油）

友元关系：是不同类间的一种特殊关系，这种特殊关系允许友元类访问对方的protected和private方法和属性。

class Lovers
{
public:
    Lovers(std::string theName);
    void kiss(Lovers *lover);
    void ask(Lovers *lover,std::string something);
    
protected:
    std::string name;
    friend class Others;//定义友元，交友了，所以可以访问Lover->name
};

class Boyfriend:public Lovers
{
public:
    Boyfriend(std::string theName);
};

class Girlfriend:public Lovers
{
public:
    Girlfriend(std::string theName);
};

class Others
{
public:
    Others(std::string theName);
    void kiss(Lovers *lover);
protected:
    std::string name;
};

void Lovers::kiss(Lovers *lover)
{
    std::cout << name << "亲亲我们家的"
    << lover->name << std::endl;
}

void Lovers::ask(Lovers *lover, std::string something)
{
    std::cout << "宝贝儿"
    << lover->name << "帮我"
    << something << std::endl;
}
/**
 *
 *构造器
 */
Lovers::Lovers(std::string theName)
{
    name = theName;
}
Boyfriend::Boyfriend(std::string theName) :Lovers(theName)
{
    
}
Girlfriend::Girlfriend(std::string theName):Lovers(theName)
{
    
}

Others::Others(std::string theName)
{
    name = theName;
}

void Others::kiss(Lovers *lover)
{
    //lover->name是受保护的，不是Lover的子类根本使用不了的。（友元就解决的该问题了）
    std::cout << name << "亲一下"
    << lover->name << std::endl;
}

int main(int argc, const char * argv[])
{
    Boyfriend boyfriend("A君");
    Girlfriend girlfriend("B妞");
    
    Others others("路人甲");
    
    girlfriend.kiss(&boyfriend);
    girlfriend.ask(&boyfriend,"洗衣服啦");
    
    std::cout << "
当当当当！传说中的路人甲登场.........
";
    others.kiss(&girlfriend);
    
    
    return 0;
}

控制台返回的结果：

B妞亲亲我们家的A君
宝贝儿A君帮我洗衣服啦

当当当当！传说中的路人甲登场.........
路人甲亲一下B妞