디자인 패턴 - 옵저버 패턴

옵저버패턴

한 객체의 상태가 바뀌면 그 객체를 의존하는 다른 객체에도 자동으로 갱신되는 방식으로 일대다(one to many) 의존성을 지닌다.

Watcher.java**

package observer.java.util.observer;

import java.util.Observable;

/**
 * <https://examples.javacodegeeks.com/core-java/util/observer/java-util-observer-example/>
 * <http://egloos.zum.com/iilii/v/3902774>
 *
 * 변화를 통보하는 중계기
 *
 * @author 정명성
 * @create date : 2016. 5. 6.
 * observer.java.util.observer.KoreaWeatherCenter.java
 */
public class Watcher extends Observable {

    public void setWeather(String weather) {
        setChanged();
        notifyObservers(weather);
    }
}

koreanWeatherCenter.java**

package observer.java.util.observer;

import java.util.Observable;
import java.util.Observer;

public class KoreaWeatherCenter implements Observer {
    private String weather;

    @Override
    public void update(Observable o, Object arg) {
        if (o instanceof Watcher) {
            this.weather = (String) arg;
            System.out.println("오늘의 날씨는 " + weather + "입니다.");

        }
    }
}

NewyorkWeatherCenter.java

package observer.java.util.observer;

import java.util.Observable;
import java.util.Observer;

public class NewyorkWeatherCenter implements Observer {

    private String weather;

    @Override
    public void update(Observable o, Object arg) {
        if (o instanceof Watcher) {
            this.weather = (String) arg;
            System.out.println("today is wheater " + weather);
        }
    }
}

Demo.java

package observer.java.util.observer;

public class Demo {
    public static void main(String[] args) {
        Watcher watcher = new Watcher();

        KoreaWeatherCenter kwc = new KoreaWeatherCenter();
        NewyorkWeatherCenter nwc = new NewyorkWeatherCenter();

        watcher.addObserver(kwc);
        watcher.addObserver(nwc);

        System.out.println("날씨변함");
        watcher.setWeather("windy");

        System.out.println("날씨변함");
        watcher.setWeather("맑음");
    }
}

https://github.com/audtjddld/pattern/tree/master/pattern/src/observer

https://github.com/audtjddld/pattern

audtjddld/patternContribute to pattern development by creating an account on GitHub.github.com

—————————– 2016. 11. 11 ——————

java script로 해봤다.

var subject = {
  arr : new Array(),
  state : 1,
  setState : function(value) {
    this.state = value;
    this.updateNotice();
  },
  attach : function (obj) {
   this.arr.push(obj);
  },
  getState : function() {
    return obj.state + this.state;
  },
  updateNotice: function() {
    for(var i = 0; i < this.arr.length; i++) {
      this.arr[i].update();
    }
  }
}

var observe =  {

  add : function(subject) {
    subject.attach(this);
    subject.state = 3;
  },
  update : function () {
    console.log('observe ' + subject.state);
  }
}

var observe2 = {
  add :function(subject) {
   subject.attach(this);
  },
  update : function() {
     console.log('observe2 ' + subject.state);
  }
}

subject.setState(3);