Visitor_Pattern - 8BitsCoding/RobotMentor GitHub Wiki

int _tmain(int argc, _TCHAR* argv[])
{
    // 부품 생성
    Wheel mWheel[4] = { "front left", "front right", "back left", "back right" };
    Engine mEngine;
    Body mBody;
    Car mCar;
 
    // 파트 추가
    mCar.append(&mWheel[0]);
    mCar.append(&mWheel[1]);
    mCar.append(&mWheel[2]);
    mCar.append(&mWheel[3]);
    mCar.append(&mEngine);
    mCar.append(&mBody);
 
    // visitor 생성
    CarPrintVisitor mCarPrintVisitor;
    CarStartVisitor mCarStartVisitor;
 
    // visitor accept 처리
    mCar.accept(&mCarPrintVisitor);
    mCar.accept(&mCarStartVisitor);
 
    return 0;
}

class Visitor;
class Element
{
public:
    virtual void accept(Visitor* v) = 0;
};

class Wheel : public Element
{
public:
    Wheel(const TCHAR* name) : mName(name) {}
 
public:
    void accept(Visitor* v) override;
    const TCHAR* getName() const { return mName.c_str(); }
 
private:
    tstring mName;
};

class Engine : public Element
{
public:
    void accept(Visitor* v) override;
};

class Car : public Element 
{
public:
    void append(Element* e) { mList.push_back(e); }
    void accept(Visitor* v) override;
 
private:
    list<Element*> mList;
};

// Visitor 인터페이스
class Visitor
{
public:
    virtual void visit(Wheel* e) = 0;
    virtual void visit(Engine* e) = 0;
    virtual void visit(Body* e) = 0;
    virtual void visit(Car* e) = 0;
};
 
//------------------------------------------------------------------
// CarPrintVisitor 상속 클래스
class CarPrintVisitor : public Visitor
{
public:
    void visit(Wheel* e) override { cout << "Visiting " << e->getName() << " Wheel" << endl; }
    void visit(Engine* e) override { cout << "Visiting engine" << endl; }
    void visit(Body* e) override { cout << "Visiting body" << endl; }
    void visit(Car* e) override { cout << "Visiting car" << endl; }
};
 
//------------------------------------------------------------------
// CarStartVisitor 상속 클래스
class CarStartVisitor : public Visitor
{
public:
    void visit(Wheel* e) override { cout << "Kicking my " << e->getName() << " Wheel" << endl; }
    void visit(Engine* e) override { cout << "Starting my engine" << endl; }
    void visit(Body* e) override { cout << "Moving my body" << endl; }
    void visit(Car* e) override { cout << "Starting my car" << endl; }
};

// 전방 선언에 따른 하단 구현
void Wheel::accept(Visitor* v) { v->visit(this); }
void Engine::accept(Visitor* v) { v->visit(this); }
void Body::accept(Visitor* v) { v->visit(this); }

// 여기서 Car에서 accept를 할 시 Car가 관리하는 모든 오브젝트에 접근
void Car::accept(Visitor* v) { for (auto i = mList.begin(); i != mList.end(); ++i) (*i)->accept(v); v->visit(this); }