Interface in C++/ Virtual

#include <iostream>
#include <string>
//interface
class Printable {
public:
    virtual std::string GetClassName() = 0;
};

class Entity : public Printable{
public:
    virtual std::string GetName() { return "Entity!"; }
    std::string GetClassName() { return "Entity!"; } // 如果没有接口里面的方法 就无法实例化
};

class Player : public Entity {
private:
    std::string m_Name;
public:
    Player(const std::string& name)
        : m_Name(name) {}
    //std::string GetName() override { return m_Name; } 
    std::string GetClassName() override { return m_Name; }
};

void Print(Printable* obj) {
    std::cout << obj->GetClassName() << std::endl;
}

class A : public Printable {
public:
    std::string GetClassName() { return "A"; }
};

void PrintName(Entity* entity) {
    std::cout << entity->GetName() << std::endl;
}

int main() {
    Entity* e = new Entity();

    Player* p = new Player("Steven!");
    Print(e);
    Print(p);
    Print(new A());
    std::cin.get();
}