타입스크립트로 작성된 옵서버

옵서버 패턴은 일부 객체들이 다른 객체들에 자신의 상태 변경에 대해 알릴 수 있는 행동 디자인 패턴입니다.

옵서버 패턴은 구독자 인터페이스를 구현하는 모든 객체에 대한 이러한 이벤트들을 구독 및 구독 취소하는 방법을 제공합니다.

복잡도:

인기도:

사용 사례들: 옵서버 패턴은 타입스크립트 코드, 특히 그래픽 사용자 인터페이스 컴포넌트들에서 매우 일반적입니다. 다른 객체들과의 클래스들과 결합하지 않고 해당 객체들에서 발생하는 이벤트들에 반응하는 방법을 제공합니다.

식별: 옵서버 패턴은 들어오는 메서드들을 목록에 저장하는 구독 메서드로 초기 식별할 수 있으며, 만약 위 구독 메서드가 목록의 객체들을 순회하고 그들의 '업데이트' 메서드를 호출하면 해당 패턴은 옵서버 패턴으로 확정지을 수 있습니다.

개념적인 예시

이 예시는 옵서버 패턴의 구조를 보여주고 다음 질문에 중점을 둡니다:

패턴은 어떤 클래스들로 구성되어 있나요?
이 클래스들은 어떤 역할을 하나요?
패턴의 요소들은 어떻게 서로 연관되어 있나요?

index.ts: 개념적인 예시

/**
 * The Subject interface declares a set of methods for managing subscribers.
 */
interface Subject {
    // Attach an observer to the subject.
    attach(observer: Observer): void;

    // Detach an observer from the subject.
    detach(observer: Observer): void;

    // Notify all observers about an event.
    notify(): void;
}

/**
 * The Subject owns some important state and notifies observers when the state
 * changes.
 */
class ConcreteSubject implements Subject {
    /**
     * @type {number} For the sake of simplicity, the Subject's state, essential
     * to all subscribers, is stored in this variable.
     */
    public state: number;

    /**
     * @type {Observer[]} List of subscribers. In real life, the list of
     * subscribers can be stored more comprehensively (categorized by event
     * type, etc.).
     */
    private observers: Observer[] = [];

    /**
     * The subscription management methods.
     */
    public attach(observer: Observer): void {
        const isExist = this.observers.includes(observer);
        if (isExist) {
            return console.log('Subject: Observer has been attached already.');
        }

        console.log('Subject: Attached an observer.');
        this.observers.push(observer);
    }

    public detach(observer: Observer): void {
        const observerIndex = this.observers.indexOf(observer);
        if (observerIndex === -1) {
            return console.log('Subject: Nonexistent observer.');
        }

        this.observers.splice(observerIndex, 1);
        console.log('Subject: Detached an observer.');
    }

    /**
     * Trigger an update in each subscriber.
     */
    public notify(): void {
        console.log('Subject: Notifying observers...');
        for (const observer of this.observers) {
            observer.update(this);
        }
    }

    /**
     * Usually, the subscription logic is only a fraction of what a Subject can
     * really do. Subjects commonly hold some important business logic, that
     * triggers a notification method whenever something important is about to
     * happen (or after it).
     */
    public someBusinessLogic(): void {
        console.log('\nSubject: I\'m doing something important.');
        this.state = Math.floor(Math.random() * (10 + 1));

        console.log(`Subject: My state has just changed to: ${this.state}`);
        this.notify();
    }
}

/**
 * The Observer interface declares the update method, used by subjects.
 */
interface Observer {
    // Receive update from subject.
    update(subject: Subject): void;
}

/**
 * Concrete Observers react to the updates issued by the Subject they had been
 * attached to.
 */
class ConcreteObserverA implements Observer {
    public update(subject: Subject): void {
        if (subject instanceof ConcreteSubject && subject.state < 3) {
            console.log('ConcreteObserverA: Reacted to the event.');
        }
    }
}

class ConcreteObserverB implements Observer {
    public update(subject: Subject): void {
        if (subject instanceof ConcreteSubject && (subject.state === 0 || subject.state >= 2)) {
            console.log('ConcreteObserverB: Reacted to the event.');
        }
    }
}

/**
 * The client code.
 */

const subject = new ConcreteSubject();

const observer1 = new ConcreteObserverA();
subject.attach(observer1);

const observer2 = new ConcreteObserverB();
subject.attach(observer2);

subject.someBusinessLogic();
subject.someBusinessLogic();

subject.detach(observer2);

subject.someBusinessLogic();

Output.txt: 실행 결과

Subject: Attached an observer.
Subject: Attached an observer.

Subject: I'm doing something important.
Subject: My state has just changed to: 6
Subject: Notifying observers...
ConcreteObserverB: Reacted to the event.

Subject: I'm doing something important.
Subject: My state has just changed to: 1
Subject: Notifying observers...
ConcreteObserverA: Reacted to the event.
Subject: Detached an observer.

Subject: I'm doing something important.
Subject: My state has just changed to: 5
Subject: Notifying observers...