Matlab享元模式

享元模式(flyweight)通过共享技术实现相同或相似对象的重用，可以减少创建对象的数量，以减少内存占用和提高性能。java string的常量池，python logging，线程池，数据库连接池都用到了享元模式。享元模式与单例模式类似，都具有共享变量的特征。本文通过使用matlab语言对享元模式进行实现。

 iflyweight.m

classdef iflyweight < handle
    methods(abstract)
        print(~);
    end
end

flyweight.m

classdef flyweight < iflyweight
    properties
        color
    end   
    methods
        function obj = flyweight(color)
            obj.color =  color;
        end
        function print(obj)
            disp("color:"+obj.color)
        end
    end
end

flyweightfactory.m

classdef flyweightfactory < handle    
    methods(static)
        function res = getflyweightmap()
            persistent flyweightmap;
            if isempty(flyweightmap) || ~isvalid(flyweightmap)
                flyweightmap = containers.map();
            end
            res = flyweightmap;
        end
        function obj = getflyweight(color)
            flyweightmap = flyweightfactory.getflyweightmap();
            if(~flyweightmap.iskey(color))
                flyweightmap(color) = flyweight(color);
            end
            obj = flyweightmap(color);
        end
        function size = getflyweightmapsize()
            flyweightmap = flyweightfactory.getflyweightmap();
            size = flyweightmap.length();
        end
    end
end

测试代码

fw1 = flyweightfactory.getflyweight('red');
fw2 = flyweightfactory.getflyweight('blue');
fw3 = flyweightfactory.getflyweight('red');
fw1.print();
fw2.print();
fw3.print();
disp(flyweightfactory.getflyweightmapsize());
clear('flyweightfactory');