C++:派生模板 class 和基础 class 之间的向下转型和向上转型?

C++: downcasting and upcasting between derived template class and base class?

我无法将指向模板派生 class 的指针转换为基本 class 指针以存储在地图中(显然稍后会检索它。)。我有:

#include <map>
//Role.h
class RoleBase{};
enum class RoleEnum : int;

template<RoleEnum role>
class Role : public RoleBase{};

//Relationship.h
class Relationship{
public:
    template<RoleEnum role>
    Role<role>* getRole(){
    auto it=RoleMap.find(role);
    if ( it == RoleMap.end() ) {
       return nullptr;
    } else {
            RoleBase* roleBase= it->second;
            return static_cast<Role<role>* >(roleBase);
        }
    }
    std::map<RoleEnum,RoleBase*> RoleMap;
};

//squash.h
enum class RoleEnum : int
{
    Player,
    Referee
};

template<> class Role<RoleEnum::Player>{};
template<> class Role<RoleEnum::Referee>{};

class SquashGame: public Relationship{
public:
    SquashGame(){
        RoleBase* playerRole=new Role<RoleEnum::Player>; //problematic
        RoleMap.emplace(RoleEnum::Player,playerRole);
    }
};

int main() {
    SquashGame squashGame;
    squashGame.getRole<RoleEnum::Player>();
    return 0;
}

为什么会这样,有没有办法解决这个问题,这样我就可以用枚举值模板化 class,以便通过 getClass<Enum> 函数进行外部调用,希望在例如?

问题很简单:你重新定义了角色

template<> class Role<RoleEnum::Player> {}

不扩展 RoleBase.

删除它或将其更改为:

template<> class Role<RoleEnum::Player> : public RoleBase {}