/**
 * 观察者模式
 *
 * 场景：当天气更新以后，动态的去通知所有关注天气预报的人
 *
 * <p>
 * 参考：https://www.runoob.com/design-pattern/observer-pattern.html
 *
 * @author zls
 * @date 2020/6/18
 */
public class ObserverDemo {
    public static void main(String[] args) {
        WeatherSubject weatherSubject = new WeatherSubject();

        new Male("高露", weatherSubject);
        new Female("黄梦莹", weatherSubject);

        weatherSubject.setState("天气晴");
        System.out.println("-------- 天气预报改变了自动的去通知 -------");
        weatherSubject.setState("天气小雨");
    }
}

/**
 * 被观察者接口
 */
@Data
abstract class Person {
    // 姓名
    public String name;
    // 持有天气预报(关注的都是同一个天气预报)
    protected WeatherSubject weatherSubject;

    // 接收消息
    public abstract void receive();
}

/**
 * 创建实体观察者类
 */
class Male extends Person {

    public Male(String name, WeatherSubject weatherSubject) {
        this.name = name;
        this.weatherSubject = weatherSubject;
        this.weatherSubject.attach(this);
    }

    @Override
    public void receive() {
        System.out.println( this.name + "(男)接收到了天气预报：" + weatherSubject.getState());
    }
}

class Female extends Person {

   public Female(String name, WeatherSubject weatherSubject) {
        this.name = name;
        this.weatherSubject = weatherSubject;
        this.weatherSubject.attach(this);
    }

    @Override
    public void receive() {
        System.out.println( this.name + "(女)接收到了天气预报：" + weatherSubject.getState());
    }
}


/**
 * 主题
 */
class WeatherSubject {

    private List<Person> persons = new ArrayList<>();

    // 天气状态
    private String state;

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
        notifyAllObservers();
    }

    /**
     * 将所有关注天气预报的人保存起来
     * @param person
     */
    public void attach(Person person) {
        System.out.println(person.getName() + "关注了天气预报");
        persons.add(person);
    }

    /**
     * 通知所有的观察者
     */
    public void notifyAllObservers() {
        for (Person person : persons) {
            person.receive();
        }
    }
}