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