Matlab组合模式

组合模式(composite)，将对象组合成树形结构以表示“部分-整体”的层次结构，组合模式使得用户对单个对象和组合对象的使用具有一致性。组合模式的目的是让客户端不再区分操作的是组合对象(composite)还是叶子对象(leaf)，而是以一个统一的方式来操作。实现这个目标的关键之处，是设计一个抽象的组件类，让它可以代表组合对象和叶子对象。这样一来，客户端就不用区分到底是组合对象还是叶子对象了，只需要全部当成组件对象进行统一的操作就可以了。计算机系统的文件夹相当于组合模式的composite，文件相当于组合模式的leaf。本文按照下面的类图，用matlab代码实现组合模式。

component.m

classdef component < handle & matlab.mixin.heterogeneous
    properties(access = protected)
        name
    end
    methods
        function obj = component(name)
            obj.name = name;
        end
    end
    methods(abstract)
        add(~,~);
        remove(~,~);
        display(~,~);
    end
    methods(sealed)   
        function res = eq(obj1,obj2)
            res = eq@handle(obj1,obj2);
        end
        function res = ne(obj1,obj2)
            res = ne@handle(obj1,obj2);
        end
    end 
end

composite.m

classdef composite < component
    properties(access = private)
        children = component.empty();
    end    
    methods
        function obj = composite(name)
           obj = obj@component(name);
        end        
        function add(obj,c)
            obj.children(end + 1)=c;
        end
        function remove(obj,c)
            index = [obj.children] ~= c;
            obj.children = obj.children(index);
        end
        function display(obj,depth)
            temp = "";
            for i = 1:depth
                temp = temp + "-";
            end
            disp(temp + obj.name);
            for i = 1:length(obj.children)
                obj.children(i).display(depth + 1);
            end
        end
    end
end

leaf.m

classdef leaf < component
    methods
        function obj = leaf(name)
           obj = obj@component(name);
        end       
        function add(~,~)          
        end
        function remove(~,~)           
        end
        function display(obj,depth)
            temp = "";
            for i = 1:depth
                temp = temp + "-";
            end
            disp(temp + obj.name);
        end
    end
end

测试代码

root = composite("composite root");
compx = composite("composite x");
root.add(leaf("leaf a"));
root.add(compx);
root.add(leaf("leaf b"));
compx.add(leaf("leaf xa"));
compx.add(leaf("leaf xb"));
compxy = composite("composite xy");
compx.add(compxy);
leafxya = leaf("leaf xya");
compxy.add(leafxya);
compxy.add(leaf("leaf xyb"));
compxy.remove(leafxya);
root.display(0);