rtti1.cpp

一本很好的C++学习的丛书！初学者必看的

// rtti1.cpp -- using the RTTI dynamic_cast operator
#include <iostream>
#include <cstdlib>
#include <ctime>

using std::cout;

class Grand
{
private:
    int hold;
public:
    Grand(int h = 0) : hold(h) {}
    virtual void Speak() const { cout << "I am a grand class!\n";}
    virtual int Value() const { return hold; }
};

class Superb : public Grand
{
public:
    Superb(int h = 0) : Grand(h) {}
    void Speak() const {cout << "I am a superb class!!\n"; }
    virtual void Say() const
        { cout << "I hold the superb value of " << Value() << "!\n";}
};

class Magnificent : public Superb
{
private:
    char ch;
public:
    Magnificent(int h = 0, char c = 'A') : Superb(h), ch(c) {}
    void Speak() const {cout << "I am a magnificent class!!!\n";}
    void Say() const {cout << "I hold the character " << ch <<
               " and the integer "  << Value() << "!\n"; }
};

Grand * GetOne();

int main()
{
    std::srand(std::time(0));
    Grand * pg;
    Superb * ps;
    for (int i = 0; i < 5; i++)
    {
        pg = GetOne();
        pg->Speak();
        if( ps = dynamic_cast<Superb *>(pg))
            ps->Say();
    }
    return 0;
}

Grand * GetOne()    // generate one of three kinds of objects randomly
{
    Grand * p;
    switch( std::rand() % 3)
    {
    case 0: p = new Grand(std::rand() % 100);
                    break;
        case 1: p = new Superb(std::rand() % 100);
                    break;
        case 2: p = new Magnificent(std::rand() % 100, 
                              'A' + std::rand() % 26);
                    break;
    }
    return p; 
}