我在将模板化派生类的指针转换为基类指针以存储在映射中(显然稍后会检索它)时遇到了麻烦。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;
}
为什么是这样,是否有一种方法来修复,这样我就可以模板一个类与枚举值通过getClass<Enum>
函数外部调用的目的,希望在示例中清楚?
问题很简单:你对角色的重新定义
template<> class Role<RoleEnum::Player> {}
不扩展RoleBase。
将其删除或更改为:
template<> class Role<RoleEnum::Player> : public RoleBase {}