فروم بچه های تولز

#include <iostream>#include <memory> struct Base {     int a;     virtual void f() const { std::cout << "I am base!n";}    virtual ~Base(){}}; struct Derived : Base{    void f() const override    { std::cout << "I am derived!n"; }    ~Derived(){}}; int main(){    auto basePtr = std::make_shared<Base>();    std::cout << "Base pointer says: ";    basePtr->f();     auto derivedPtr = std::make_shared<Derived>();    std::cout << "Derived pointer says: ";    derivedPtr->f();     // static_pointer_cast to go up class hierarchy    basePtr = std::static_pointer_cast<Base>(derivedPtr);    std::cout << "Base pointer to derived says: ";    basePtr->f();     // dynamic_pointer_cast to go down/across class hierarchy    auto downcastedPtr = std::dynamic_pointer_cast<Derived>(basePtr);    if(downcastedPtr)    {         std::cout << "Downcasted pointer says: ";        downcastedPtr->f();     }     // All pointers to derived share ownership    std::cout << "Pointers to underlying derived: "             << derivedPtr.use_count()             << "n"; }