C++标准转换运算符dynamic_cast

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             cast_operator_comparison.cpp                                                      

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             Language:   C++                   

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             Complier:    Visual Studio 2010, Xcode3.2.6 

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             Platform:    MacBook Pro 2010

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             Application:  none  

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             Author:      Ider, Syracuse University  ider.cs@gmail.com
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#include <string>
#include <iostream>
usingnamespace std;

class Parents
{
public:
    Parents(string n="Parent"){ name = n;}
    virtual ~Parents(){}

    virtualvoid Speak()
    {
        cout << "\tI am " << name << ", I love my children." << endl;
    }
    void Work()
    {
        cout << "\tI am " << name <<", I need to work for my family." << endl;;
    }
protected:
    string name;
};

class Children : public Parents
{
public:
    Children(string n="Child"):Parents(n){ }

    virtual ~Children(){}

    virtualvoid Speak()
    {
        cout << "\tI am " << name << ", I love my parents." << endl;
    }
    /*
     **Children inherit Work() method from parents,
     **it could be treated like part-time job.
     */void Study()
    {
        cout << "\tI am " << name << ", I need to study for future." << endl;;
    }
    
private:
    //string name; //Inherit "name" member from Parents};

class Stranger 
{
public:
    Stranger(string n="stranger"){name = n;}
    virtual ~Stranger(){}

    void Self_Introduce()
    {
        cout << "\tI am a stranger" << endl;
    }
    void Speak()
    {
        //cout << "I am a stranger" << endl;
        cout << "\tDo not talk to "<< name << ", who is a stranger." << endl;
    }
private:
    string name;
};

int main() {
    
    /******* cast from child class to base class *******/
    cout << "dynamic_cast from child class to base class:" << endl;
    Children * daughter_d = new Children("Daughter who pretend to be my mother");
    Parents * mother_d = dynamic_cast<Parents*> (daughter_d); //right, cast with polymorphism
    mother_d->Speak();
    mother_d->Work();
    //mother_d->Study(); //Error, no such method    
    cout << "static_cast from child class to base class:" << endl;
    Children * son_s = new Children("Son who pretend to be my father");
    Parents * father_s = static_cast<Parents*> (son_s); //right, cast with polymorphism
    father_s->Speak();    
    father_s->Work();
    //father_s->Study(); //Error, no such method    
    cout << endl;
    
    /******* cast from base class to child class *******/    
    cout << "dynamic_cast from base class to child class:" << endl;
    Parents * father_d = new Parents("Father who pretend to be a my son");
    Children * son_d = dynamic_cast<Children*> (father_d); //no error, but not safeif (son_d)
    {
        son_d->Speak();
        son_d->Study();
    }
    else cout << "\t[null]" << endl;
    
    cout << "static_cast from base class to child class:" << endl;
    Parents * mother_s = new Parents("Mother who pretend to be a my daugher");
    Children * daughter_s = static_cast<Children*> (mother_s);  //no error, but not safeif (daughter_s)
    {
        daughter_s->Speak();
        daughter_s->Study();
    }
    else cout << "\t[null]" << endl;
    
    cout << endl;
    
    /******* cast between non-related class *******/    
    cout << "dynamic_cast to non-related class:" << endl;
    Stranger* stranger_d = dynamic_cast<Stranger*> (daughter_d);
    if (stranger_d)
    {
        stranger_d->Self_Introduce();
        stranger_d->Speak();    
    }
    else cout <<"\t[null]"<<endl;
    
    //Stranger* stranger_s = static_cast<Stranger*> (son_s);    //Error, invalid cast    
    cout << "reinterpret_cast to non-related class:" << endl;
    Stranger* stranger_r = reinterpret_cast<Stranger*> (son_s);
    if (stranger_r)
    {
        stranger_d->Self_Introduce();
        //stranger_d->Speak();    //This line would cause program crush,
        //as "name" could not be found corretly.    }
    else cout << "\t[null]" << endl;

    cout << endl;
    
    /******* cast back*******/
    cout << "use dynamic_cast to cast back from static_cast:" << endl;
    Children* child_s = dynamic_cast<Children*> (father_s);
    if (child_s)
    {
        child_s->Speak();
        child_s->Work();
    }
    else cout << "\t[null]" << endl;
    
    //cout<<typeid(stranger_r).name()<<endl;    
    cout << "use dynamic_cast to cast back from reinterpret_cast:" << endl;
    Children* child_r = dynamic_cast<Children*> (stranger_r);
    if (child_r)
    {
        child_r->Speak();
        child_r->Work();
    }
    else cout << "\t[null]" << endl;
    
    delete daughter_d;
    delete son_s;
    delete father_d;
    delete mother_s;
    
    return0;
}

/********************* Result *********************///dynamic_cast from child class to base class:
//    I am Daughter who pretend to be my mother, I love my parents.
//    I am Daughter who pretend to be my mother, I need to work for my family.
//static_cast from child class to base class:
//    I am Son who pretend to be my father, I love my parents.
//    I am Son who pretend to be my father, I need to work for my family.
////dynamic_cast from base class to child class:
//    [null]
//static_cast from base class to child class:
//    I am Mother who pretend to be a my daugher, I love my children.
//    I am Mother who pretend to be a my daugher, I need to study for future.
////dynamic_cast to non-related class:
//    [null]
//reinterpret_cast to non-related class:
//    I am a stranger
////use dynamic_cast to cast back from static_cast:
//    I am Son who pretend to be my father, I love my parents.
//    I am Son who pretend to be my father, I need to work for my family.
//use dynamic_cast to cast back from reinterpret_cast:
//    [null]

1. C++ Language Tutorial - Type Casting
2. Object Oriented Design
3. IBM Complilers - XL C/C++ V9.0 for Linux - The dynamic_cast operator (C++ only)
4. MSDN Visual C++ Develope Center - dynamic_cast Operator
5. In C++, what’s a virtual destructor and when is it needed?
6. Wikipedia The Free Encyclopedia - Run-Time Type Information
7. Wikipedia The Free Encyclopedia - Virtual Function