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);