데코레이터 패턴

데코레이터 패턴(Decorator pattern)이란 주어진 상황 및 용도에 따라 어떤 객체에 책임을 덧붙이는 패턴으로, 기능 확장이 필요할 때 서브클래싱 대신 쓸 수 있는 유연한 대안이 될 수 있다. // the Window interface interface Window { public void draw(); // draws the Window public String getDescription(); // returns a description of the Window } // implementation of a simple Window without any scrollbars class SimpleWindow implements Window { public void draw() { // draw window } public String getDescription() { return "simple window"; } } 아래의 클래스들은 모든 Window 클래스들의 데코레이터를 포함하고 있다. // abstract decorator class - note that it implements Window abstract class WindowDecorator implements Window { protected Window decoratedWindow; // the Window being decorated public WindowDecorator (Window decoratedWindow) { this.decoratedWindow = decoratedWindow; } } // the first concrete decorator which adds vertical scrollbar functionality class VerticalScrollBarDecorator extends WindowDecorator { public VerticalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } public void draw() { drawVerticalScrollBar(); decoratedWindow.draw(); } private void drawVerticalScrollBar() { // draw the vertical scrollbar } public String getDescription() { return decoratedWindow.getDescription() + ", including vertical scrollbars"; } } // the second concrete decorator which adds horizontal scrollbar functionality class HorizontalScrollBarDecorator extends WindowDecorator { public HorizontalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } public void draw() { drawHorizontalScrollBar(); decoratedWindow.draw(); } private void drawHorizontalScrollBar() { // draw the horizontal scrollbar } public String getDescription() { return decoratedWindow.getDescription() + ", including horizontal scrollbars"; } } Window 인스턴스를 만드는 테스트 프로그램은 아래와 같다. public class DecoratedWindowTest { public static void main(String[] args) { // create a decorated Window with horizontal and vertical scrollbars Window decoratedWindow = new HorizontalScrollBarDecorator ( new VerticalScrollBarDecorator(new SimpleWindow())); // print the Window's description System.out.println(decoratedWindow.getDescription()); } } #include <iostream> using namespace std; /* Component (interface) */ class Widget { public: virtual void draw() = 0; virtual ~Widget() {} }; /* ConcreteComponent */ class TextField : public Widget { private: int width, height; public: TextField( int w, int h ){ width = w; height = h; } void draw() { cout << "TextField: " << width << ", " << height << '\n'; } }; /* Decorator (interface) */ class Decorator : public Widget { private: Widget* wid; // reference to Widget public: Decorator( Widget* w ) { wid = w; } void draw() { wid->draw(); } ~Decorator() { delete wid; } }; /* ConcreteDecoratorA */ class BorderDecorator : public Decorator { public: BorderDecorator( Widget* w ) : Decorator( w ) { } void draw() { Decorator::draw(); cout << " BorderDecorator" << '\n'; } }; /* ConcreteDecoratorB */ class ScrollDecorator : public Decorator { public: ScrollDecorator( Widget* w ) : Decorator( w ) { } void draw() { Decorator::draw(); cout << " ScrollDecorator" << '\n'; } }; int main( void ) { Widget* aWidget = new BorderDecorator( new ScrollDecorator( new TextField( 80, 24 ))); aWidget->draw(); delete aWidget; } 컴포지트 패턴 어댑터 패턴 관점 지향 프로그래밍 불변객체 위키책에 이 문서와 관련된 문서가 있습니다. Decorator implementations in various languages Decorator pattern description from the Portland Pattern Repository