小编pig*_*ens的帖子

#include <iostream>
using namespace std;


class  A
{
public:
    A()
    {
        cout << "A ctor" << endl;
    }
    virtual ~A()
    {
        cout << "A dtor" << endl;
    }
    virtual void foo() = 0;
};
class  B : public A
{
public:
    B()
    {
        cout << "B ctor" << endl;
    }
    virtual ~B()
    {
        cout << "B dtor" << endl;
    }
    virtual void foo()
    {
        cout <<"B's foo" << endl;
    }
};
class  C : public A
{
public:
    C() { …