蝇量模式

蝇量模式(享元模式) （flyweight）如想让某个类的一个实例能用来提供许多“虚拟实例”，就使用蝇量模式。

#include <iostream>
#include <map>
#include <stdlib.h>

using namespace std;


struct Circle {
public:
    Circle(string color) {
        this->color = color;
    }
    void setX(int x) {
        this->x = x;
    }
    void setY(int y) {
        this->y = y;
    }
    void setRadius(int radius) {
        this->radius = radius;
    }
    void draw() {
        cout << "Circle: Draw() [Color : " << color <<
         ", x : " << x << ", y : " << y <<
         ", radius : " << radius << endl;
    }
private:
    string color;
    int x;
    int y;
    int radius;
};

struct CircleFactory {
public:
    Circle *getCircle(string color) {
        Circle *circle;
        map<string, Circle *>::iterator it = circleMap.find(color);

        if (it == circleMap.end()) {
            circle = new Circle(color);
            circleMap.insert(pair<string, Circle *>(color, circle));
            cout << "Creating circle of color : " << color << endl;
        } else {
            circle = it->second;
        }
        return circle;
    }
private:
    map<string, Circle *> circleMap;
};

string colors[] = {"Red", "Green", "Blue", "White", "Black"};

string getRandomColor() {
    return colors[rand() % (sizeof(colors)/sizeof(colors[0]))];
}

int getRandomX() {
    return rand();
}

int getRandomY() {
    return rand();
}

int main(int argc, char **argv) {
    CircleFactory *circleFactory = new CircleFactory();

    for(int i=0; i < 20; ++i) {
        Circle *circle = (Circle *)circleFactory->getCircle(getRandomColor());
        circle->setX(getRandomX());
        circle->setY(getRandomY());
        circle->setRadius(100);
        circle->draw();
    }
}