dynamic_cast | CppDeveloper

6.4.5 Toán tử ép kiểu động (dynamic_cast) (1)

Tháng Mười Hai 24, 2017 Mr.Shun 0

Hãy cùng phân tích source code bên dưới (đây là source code của chương trình ở trang trước nhưng đã được thay đổi) →

#include <iostream>
#include <string>

using namespace std;

class Pet {
protected: 
    string name;
public:       
    Pet(string name) : name(name) {}
    virtual void MakeSound(void) { cout << name << " is silent" << endl; }
};

class Dog : public Pet {
public:    
    Dog(string name) : Pet(name) {}
    void MakeSound(void) { cout << name << " says: Woof!" << endl; }
};

class GermanShepherd : public Dog {
public:    
    GermanShepherd(string name) : Dog(name) {}
    void MakeSound(void) { cout << name << " says: Wuff!" << endl; }
    void Laufen(void) { cout << name << " runs (gs)!" << endl; }
};

class MastinEspanol : public Dog {
public:    
    MastinEspanol(string name) : Dog(name) {}
    void MakeSound(void) { cout << name << " says: Guau!" << endl; }
    void Ejecutar(void) { cout << name << " runs (mes)!" << endl; }
};

void PlayWithPet(Pet *pet) {
    GermanShepherd *gs;
    MastinEspanol *mes;
    pet -> MakeSound();
    
    if(gs = dynamic_cast<GermanShepherd *>(pet)) {
        gs -> Laufen();
    }
    
    if(mes = dynamic_cast<MastinEspanol *>(pet)) {
        mes -> Ejecutar();
    }
}

int main(void) {
    Pet *pet = new Pet("creature");
    Dog *dog = new Dog("Dog");
    GermanShepherd *gs = new GermanShepherd("Hund");
    MastinEspanol *mes = new MastinEspanol("Perro");
    PlayWithPet(pet);
    PlayWithPet(dog);
    PlayWithPet(gs);
    PlayWithPet(mes);
    return 0;
}

#include <iostream>

#include <string>

using namespace std;

class Pet {

protected:

string name;

public:

Pet(string name) : name(name) {}

virtual void MakeSound(void) { cout << name << " is silent" << endl; }

};

class Dog : public Pet {

public:

Dog(string name) : Pet(name) {}

void MakeSound(void) { cout << name << " says: Woof!" << endl; }

};

class GermanShepherd : public Dog {

public:

GermanShepherd(string name) : Dog(name) {}

void MakeSound(void) { cout << name << " says: Wuff!" << endl; }

void Laufen(void) { cout << name << " runs (gs)!" << endl; }

};

class MastinEspanol : public Dog {

public:

MastinEspanol(string name) : Dog(name) {}

void MakeSound(void) { cout << name << " says: Guau!" << endl; }

void Ejecutar(void) { cout << name << " runs (mes)!" << endl; }

};

void PlayWithPet(Pet *pet) {

GermanShepherd *gs;

MastinEspanol *mes;

pet -> MakeSound();

if(gs = dynamic_cast<GermanShepherd *>(pet)) {

gs -> Laufen();

}

if(mes = dynamic_cast<MastinEspanol *>(pet)) {

mes -> Ejecutar();

}

int main(void) {

Pet *pet = new Pet("creature");

Dog *dog = new Dog("Dog");

GermanShepherd *gs = new GermanShepherd("Hund");

MastinEspanol *mes = new MastinEspanol("Perro");

PlayWithPet(pet);

PlayWithPet(dog);

PlayWithPet(gs);

PlayWithPet(mes);

return 0;

}

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