#include <iostream>
#include <unordered_map>
#include <string>
class Top
{
public:
virtual void run(){}
virtual ~Top(){}
};
class Middle : public Top
{
void run() override { std::cout << "Middle\n"; }
};
class Buttom : public Top
{
void run() override { std::cout << "Buttom\n"; }
};
template<typename T>
class SmartPtr
{
public:
SmartPtr(T* realPtr) : ptr(realPtr){}
template<typename U>
SmartPtr(const SmartPtr<U>& other) : ptr(other.get()) {}
T* get() const { return ptr; }
template<typename U>
SmartPtr<T>* operator = (const SmartPtr<U>& other)
{
ptr = other.get();
return this;
}
T* operator -> ()
{
return ptr;
}
private:
T* ptr;
};
int main()
{
SmartPtr<Top> ptr1 = SmartPtr<Buttom>(new Buttom);
ptr1->run();
SmartPtr<Middle> ptr3(new Middle);
ptr1 = ptr3;
ptr1->run();
return 0;
}
