cpp class test

class_test.cpp

#include <iostream>

using namespace std;

class Base {
//    int a;
public:
    int a;
    Base() { a = 0; }
    Base(int x) { a = x; }
    virtual ~Base() { cout << "Delete Base instance." << endl; }

    void show(void) { cout << "[Base]" << a << endl; }

    virtual void vshow(void) { cout << "[Base]" << a << endl; }
};

class Derv : public Base {
public:
    int a, b;
    Derv(int x, int y, int z) : Base(x) { a = y; b = z; }
     ~Derv() { cout << "Delete Derv instance." << endl; }
    void show(void) { cout << "[D]" << a << " " << b << endl; }

    virtual void vshow(void) { cout << "[D]" << a << " " << b << endl; }
};

int main()
{
    Derv d = Derv(1, 2, 3);
    d.show();
    d.vshow();
    cout << "--------------" << endl;

    Base *pBase = new Derv(1,2,3);
    pBase->show();
    pBase->vshow();
    delete pBase;
    cout << "--------------" << endl;

    pBase = &d;
    pBase->show();
    pBase->vshow();
    cout << "--------------" << endl;

    return 0;
}