C++ Programming - 12th Study

7
class Baz : public Foo, public Bar
{
// Something
};

8
class Dog
{
public:
virtual void bark() { cout << "Woof!" << endl; }
};
class Bird
{
public:
virtual void chirp() { cout << "Chirp!" << endl; }
};
class DogBird : public Dog, public Bird
{ };

9
DogBird confusedAnimal;
confusedAnimal.bark();
confusedAnimal.chirp();

10
class Dog {
public:
virtual void bark() { cout << "Woof!" << endl; }
virtual void eat() { cout << "The dog has eaten." << endl; }
};
class Bird {
public:
virtual void chirp() { cout << "Chirp!" << endl; }
virtual void eat() { cout << "The bird has eaten." << endl; }
};

11
confusedAnimal.eat();
error C2385: ambiguous access of 'eat'
note: could be the 'eat' in base 'Dog'
note: or could be the 'eat' in base 'Bird'
static_cast<Dog>(confusedAnimal).eat(); // 슬라이싱, Dog::eat() 호출
confusedAnimal.Dog::eat(); // 명시적으로 Dog::eat() 호출
void DogBird::eat()
{
Dog::eat(); // 명시적으로 Dog의 eat() 호출
}

12
class Dog
{
public:
virtual void eat()
{
cout << "The bird has eaten." << endl;
}
};
class Bird : public Dog {};
class DogBird : public Bird, public Dog {};
confusedAnimal.eat();
error C2385: ambiguous access of 'eat'
note: could be the 'eat' in base 'Dog'
note: or could be the 'eat' in base 'Dog'

13
class Animal
{
public:
virtual void sleep() { cout << "Zzz..." << endl; }
};
class Dog : public Animal { … };
class Bird : public Animal { … };
confusedAnimal.sleep();
error C2385: ambiguous access of 'sleep'
note: could be the 'sleep' in base 'Animal'
note: or could be the 'sleep' in base 'Animal

14
class Animal {
public:
virtual void sleep() = 0;
};
class Dog : public Animal {
public:
virtual void sleep() { … }
};
class Bird : public Animal {
public:
virtual void sleep() { … }
};
class DogBird : public Dog, public Bird {
public:
virtual void sleep() { Dog::sleep(); }
};

15
class Animal
{
public:
virtual void sleep() { cout << "Zzz..." << endl; }
};
class Dog : public virtual Animal { … };
class Bird : public virtual Animal { … };
confusedAnimal.sleep(); // Animal이 virtual이기 때문에 모호하지 않음

17
class Super
{
public:
void go() { cout << "Super::go()" << endl; }
};
class Sub : public Super
{
public:
void go() { cout << "Sub::go()" << endl; }
};
Sub mySub;
mySub.go();
Sub::go()
Sub mySub;
Super& ref;
ref = mySub;
ref.go();
Super::go()

19
class Super
{
public:
virtual void func1() { }
};
class Sub : public Super
{
public:
};
Super mySuper;
Sub mySub;
vtable
mySuper
vtable
mySub
func1
func2
func1
func2
Super::func1()
구현부
Super::func2()
구현부
Sub::func2()
구현부

21
class Super {
public:
Super() { }
~Super() { }
};
class Sub : public Super {
private:
char* mString;
public:
Sub() { mString = new char[30]; }
~Sub() { delete[] mString; }
};
Super* ptr = new Sub(); // mString은 이 시점에 할당됨
delete ptr; // ~Super가 호출되었지만
// virtual이 아니기 때문에
// ~Sub는 호출되지 않음

24
참고 : http://prostars.net/55
#include <iostream>
using namespace std;
class Base
{
public:
virtual void print() { cout << "Base" << endl; }
};
class Derived : public Base
{
public:
virtual void print() { cout << "Derived" << endl; }
};

25
Base* base1 = new Base;
Base* base2 = new Derived;
Derived* derived1 = new Derived;
Derived* derived2 = nullptr;
// 컴파일 오류 : 타입 변환을 할 수 없다.
// derived2 = base1;
// 컴파일 성공 : 런타임에 타입 변환에 실패하며
// nullptr을 반환한다.
derived2 = dynamic_cast<Derived*>(base1);
if (derived2 == nullptr)
cout << "Runtime Error" << endl;

26
// 컴파일 오류 : 타입 변환을 할 수 없다.
// derived2 = base2;
// 컴파일 성공 : 런타임에 타입 변환에 성공하며
// Derived 타입의 포인터를 반환한다.
derived2 = dynamic_cast<Derived*>(base2);
if (derived2)
derived2->print();
// 컴파일 성공 : 이런 경우에는 캐스팅이 필요 없다.
derived2 = derived1;

27
#include <iostream>
#include <typeinfo>
using namespace std;
class Animal
{
virtual void something() { }
};
class Dog : public Animal { };
class Bird : public Animal { };
void speak(const Animal& animal) {
if (typeid(animal) == typeid(Dog&))
cout << "Woof!" << endl;
else if (typeid(animal) == typeid(Bird&))
cout << "Chirp!" << endl;
}
Dog dog;
Bird bird;
Animal& animal = dog;
speak(animal);
animal = bird;
speak(bird);
Woof!
Chirp!

C++ Programming - 12th Study

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