子类在heap开辟空间时的 纯虚析构用法示例 virtual destructor and pure virtual deconstructor

 

#include<iostream>
#include<string>
using namespace std;
class Animal
{
public:
	Animal(){ cout << "Animal virtual constructor" << endl; }

	virtual~Animal(){ cout << "Animal constructor" << endl; }//virtual destructor ---solve father release object of son
	virtual ~Animal() = 0;//pure virtual destructor  but there is only declaration,while (virtual) destructor whether pure or not need to realize
	virtual void speak() = 0;//pure virtual function
};
Animal::~Animal()//destructor relize by code where can add the release of sth father father father new in heap 
{
	cout << "pure virtual destructor" << endl;
}

class Cat :public Animal
{
	string* namep;
public:
	void speak()
	{
		cout << *namep << "cat is speaking" << endl;
	}
	Cat(string a)
	{
		cout << "Cat constructor" << endl;
		namep=new string(a);
	}
	~Cat()
	{
		if (namep != NULL)
		{
			cout << "Cat destructor" << endl;
			delete namep;
			namep = NULL;
		}
	}
};
void f0()
{
	Animal* p = new Cat("Tom");
	p->speak();//father pointer don't use destructor of son when destruct---son have sth new in heap,then memory leak
	delete p;
}
int main()
{
	f0();
	system("pause");
}