C++類繼承--基類new和用派生類new的區別

#include <stdio.h>

class Base
{
public:
	int a;
	Base(){
		a=0;
	}
	virtual ~Base(){
		printf("base delete");
	}
	virtual void setA()=0;
	
};

class A:public Base
{
public:
	A(){
		a = 10;
	}
	~A(){
		printf("A class delete\n");
	}
	virtual void setA()
	{
		a = 2;
	}
};

class B:public Base
{
public:
	B(){
		a=20;
	}
	~B(){
		a=-20;
	}
	
	virtual void setA()
	{
		a = 3;
	}
};

int main()
{
	
	Base *x = new A();
	printf("BASE: a value of a construct %d\n", x->a);
	x->setA();
	printf("BASE: a value of a %d\n", x->a);

	x = new B();
	printf("BASE: b value of b construct %d\n", x->a);
	x->setA();
	printf("BASE: B value of b %d\n", x->a);

	A *aClass = new A();
	printf("a value of a construct %d\n", aClass->a);
	aClass->setA();
	printf("a value of a %d\n", aClass->a);
	
	B *bClass = new B();
	printf("b value of a construct %d\n", bClass->a);
	bClass->setA();
	printf("b value of a %d\n", bClass->a);
	
	delete aClass;
	
	return 0;
}