How to implement the method “killing” objects? [closed]

Basically, in C ++ you can implement something like

 #include <iostream> using namespace std; struct Food { Food() { cout << "Food constructor" << endl; } ~Food() { cout << "Food destructor" << endl; } }; struct Predator { void eat(Food& food) { food.~Food(); } void eat(Food* food) { delete food; } }; int main() { Predator p; Food *f1 = new Food; Food *f2 = new Food; p.eat(*f1); p.eat(f2); return 0; } 

But, IMHO, this is bad. You can eat only dynamically created food). Although you can protect yourself from UB by prohibiting the creation of Food objects on the stack:

 #include <iostream> using namespace std; struct Food { Food() { cout << "Food constructor" << endl; } void die() { delete this; } private: ~Food() { cout << "Food destructor" << endl; } }; struct Predator { void eat(Food& food) { food.die(); } void eat(Food* food) { food->die(); } }; int main() { Predator p; Food *f1 = new Food; Food *f2 = new Food; // Food f3; --> compile time error p.eat(*f1); // delete f2; --> compile time error p.eat(f2); // f2->die(); --> а это скомпилируется, но UB, если f2 уже съеден return 0; } 

And it is possible to dissolve the whole zopark))). And in this case, both the devouring of an animal and its natural death are perfectly safe, the animal cannot die 2 times, the global function of the die notifies both the shepherd and the barn about the death of the poor creature:

 #include <iostream> using namespace std; struct Animal { virtual void eat(Animal*&) = 0; friend void ::die(Animal*&); protected: virtual void die() = 0; virtual ~Animal() {} }; void die(Animal*& a); struct Sheep : public Animal { Sheep() { cout << "Sheep constructor" << endl; } void eat(Animal*&) {/* овечка не может съесть животное */ cout << "impossible" << endl;} protected: void die() { delete this; } private: ~Sheep() { cout << "Sheep destructor" << endl; } }; struct Wolf : public Animal { void eat(Animal*& food) { ::die(food); } protected: void die() { delete this; } private: ~Wolf() {} }; int main() { Animal *s1 = new Sheep, *s2 = new Sheep, *s3 = new Sheep; Animal *w1 = new Wolf, *w2 = new Wolf; w1->eat(s1); w2->eat(s2); s3->eat(w1); // Смело... die(s3); // От старости... Или со страху. die(w1); die(w2); // Отравленные овцы?! // w1->die(); --> ошибка компиляции die(w1); // --> ничего не происходит, т.к. w1==nullptr cout << static_cast<void*>(w1) << endl << static_cast<void*>(s1) << endl; return 0; } void die(Animal*& a) { if (a != nullptr) a->die(); else cout << "Dead animal can not die. RIP" << endl; a = nullptr; } 

Thanks VladD for the links: Here is the official FAQ about delete this . And what about the explicit call of the destructor (true, only a local variable).