动态模板实例化

Question

我有一个类模板,我需要声明该类的对象,而不定义类型参数,以便我可以稍后有条件地定义它们,例如:

template<typename T>
class A{
public:
    A(T v){var = v};
    ~A(){};

    T var;
}

int main(){
    A<>* object; // Or sometihng along these lines...?
    if(/* something*/)
        object = new A<float>(0.2f);
    else{
        object = new A<int>(3);
    }
}

Answer 1

嗯,你当然不能那样做.你必须使A派生自另一个类,例如:

template<typename T>
class A : public B {
public:
    A(T v){var = v};
    ~A(){};

    T var;
}

int main(){
    B* object;
    if(/* something*/)
        object = new A<float>(0.2f);
    else{
        object = new A<int>(3);
    }
}