c++ - 基于策略的设计中的模糊继承

我有一个主机类，它有两个策略，sayhello和talk。策略talk是一个类模板，它本身需要例如sayhello。
问题是sayhello::saySomething在host2中含糊不清(我尝试使用virtual解决此菱形继承(钻石问题))。

我该如何解决这种歧义？还是总有针对此类问题的更好设计？

例:

#include <iostream>

class sayhello {
protected:
    void saySomething(void) {
        std::cout<<"Hello!"<<std::endl;
    }
};

template<typename T>
class talk : private T {
protected:
    void doSomething(void) {
        T::saySomething();
    }
};

template<typename T>
class host1 : virtual T {
public:
    void hostAction(void) {
        T::doSomething();
    }
};

template<typename T, typename L>
class host2 : private T, private L {
public:
    void hostAction(void) {
        T::doSomething();
        L::saySomething();
    }
};

int main() {
    host1<talk<sayhello> > HOST1;
    HOST1.hostAction(); // ok that works

    host2<talk<sayhello>,sayhello> HOST2;
    HOST2.hostAction(); // error, ambiguity!

    return 0;
}

最佳答案

您可能在滥用继承，但是只需在virtual和talk中添加更多host2关键字:

#include <iostream>

class sayhello {
protected:
    void saySomething(void) {
        std::cout<<"Hello!"<<std::endl;
    }
};

template<typename T>
class talk : virtual T {
protected:
    void doSomething(void) {
        T::saySomething();
    }
};

template<typename T>
class host1 : virtual T {
public:
    void hostAction(void) {
        T::doSomething();
    }
};

template<typename T, typename L>
class host2 : virtual T, virtual L {
public:
    void hostAction(void) {
        T::doSomething();
        L::saySomething();
    }
};

int main() {
    host1<talk<sayhello> > HOST1;
    HOST1.hostAction(); // ok that works

    host2<talk<sayhello>,sayhello> HOST2;
    HOST2.hostAction(); // error, ambiguity!

    return 0;
}

Live Example