Matlab观察者模式

要点：

1、服务端（subject）维护一个观察者的列表，以便能够向所有的观察者（observer）推送信息

2、观察者可以获取服务端的状态

3、服务端和观察者可抽象，可以有多个不同实现

subject.m

classdef subject < handle
    properties(access = private)
        observers = observer.empty();
    end
    methods
        function add(obj,observer)
            obj.observers(end + 1) = observer;
        end
        function rm(obj,observer)
            index = [obj.observers] ~= observer;
            obj.observers = obj.observers(index);
        end
        function notify(obj)
            for i= 1:length(obj.observers)
                obj.observers(i).update(obj);
            end
        end
    end
end

concretesubject.m

classdef concretesubject < subject    
    properties(access = public)
        news
    end   
    methods
        function set.news(obj,news)
            obj.news = news;
        end      
        function news = get.news(obj)
            news = obj.news;
        end
    end
end

observer.m

classdef observer < handle & matlab.mixin.heterogeneous
    methods(abstract)
        update(~,~);
    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

concreteobserver1.m

classdef concreteobserver1 < observer
    properties
        name
    end    
    methods
        function obj = concreteobserver1(name)
            obj.name = name;
        end
        function update(obj,subject)
            disp([obj.name, ' has got subject news: ',subject.news]);
        end
    end
end

concreteobserver2.m

classdef concreteobserver2 < observer
    properties
        name
    end
    methods
        function obj = concreteobserver2(name)
            obj.name = name;
        end
        function update(obj,subject)
            disp([obj.name, ' has received subject news: ',subject.news ]);
        end
    end
end

测试代码：

sub = concretesubject();
sub.news = 'hello matlab';
o1 = concreteobserver1('obs:a');
o2 = concreteobserver2('obs:b');
 
sub.add(o1);
sub.add(o2);
sub.notify();
 
sub.rm(o1);
sub.news = 'hello observer pattern';
sub.notify();