panda-lewandowski / design-pattern-and-containers Goto Github PK

class Image {
	protected:
		int myId;
		Image();
		~Image();
		virtual void draw() = 0;
};

class RealImage : public Image {
	public:
		RealImage(int i) { myId = i; }

		void draw() { cout << " drawing image " << myId << '\n'; }
};

class ProxyImage : public Image {
		RealImage* realImage;
		static int next;
	public:
		ProxyImage() {
			myId = next++;
			realImage = 0;
		}

		void draw() {
			if (!realImage) {
				realImage = new RealImage(myId);
			}
			realImage->draw();
		}
};

int ProxyImage::next = 1;

		Image() = default;
		~Image() = default;