Matlab观察者模式(Observer)

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 = [email protected](obj1,obj2);
        end
        function res = ne(obj1,obj2)
            res = [email protected](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();
           

测试结果：

Matlab自带event事件使用的是发布-订阅者模式，与观察者模式类似（区别参考：https://www.cnblogs.com/viaiu/p/9939301.html），代码如下：

EventObserver.m

classdef EventSubscriber < handle
    properties
        name
    end
    methods
        function obj = EventSubscriber(name)
            obj.name = name;
        end
        %可以是普通函数、静态函数和成员函数
        function dispMsg(obj,src,data)
            disp("["+data.time+"]"+obj.name + ":"+data.msg+" from "+src.name);
        end
    end
end
           

EventPublisher.m

classdef EventPublisher < handle
    events
        msgRecv
    end
    properties
        name
    end
    methods
        function obj = EventPublisher(name)
            obj.name = name;
        end
        function sendMsg(obj,msg)
           obj.notify('msgRecv',EventMessage(msg));
        end
    end
end
           

EventMessage.m

classdef EventMessage < event.EventData
    properties
        msg
        time
    end
    methods
        function obj = EventMessage(msg)
            obj.time = datestr(now);
            obj.msg = msg;
        end
    end
end
           

测试代码：

pub = EventPublisher("pub1");
sub = EventSubscriber("sub1");
h = pub.addlistener('msgRecv',@sub.dispMsg);
pub.sendMsg("matlab event");
delete(h);
pub.sendMsg("matlab event");
           

 运行结果：