动态模板实例化 [英] Dynamic Template Instantiation

问题描述

我有一个类模板，我需要声明该类的对象，而无需定义类型参数，以便稍后可以有条件地定义它们，例如：

I've got a class template, and I need to declare an object of that class, without defining the type parameters, so that I can define them conditionally later, e.g.:

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);
    }
}

推荐答案

，您当然无法做到。您必须使A衍生自另一个类，例如：

Well, you certainly can't do that. You'll have to make A derive from another class, for example:

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);
    }
}

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