Observer Pattern in Typescript

observer_pattern_typescript

interface IObserver { 
    update(): void;
}

interface IObservable {
    add(observer: IObserver): void;
    remove(Obsever: IObserver): void;
    notify(): void;
}

class WeatherStation implements IObservable {

    private observers: IObserver[] = []

    constructor() { 
        setInterval(() => this.notify(), 1500);
    }

    add = (observer: IObserver): IObservable => {
        this.observers.push(observer);
        return this;
    };

    remove = (observer: IObserver): void => { 
        this.observers = this.observers.filter(obs => observer !== obs);
    };

    notify = (): void => this.observers.forEach(observer => observer.update());

    getTemperature = (): Number => Math.random() * 1000;
}

class PhoneDisplay implements IObserver {
    constructor(private weatherStation: WeatherStation) { }
    update = (): void => console.log('[PhoneDisplay] temperature: ', this.weatherStation.getTemperature());
}

class HardwareDisplay implements IObserver {
    constructor(private weatherStation: WeatherStation) { }
    update = (): void => console.log('[HardwareDisplay] temperature: ', this.weatherStation.getTemperature());
}

// Annonymous Test Class 
new class ObserverPatternTests {
    run = () => {

        const station: WeatherStation = new WeatherStation();
        const phone: IObserver = new PhoneDisplay(station);
        const hardware: IObserver = new HardwareDisplay(station);

        station
            .add(phone)
            .add(hardware);
    }
}().run();

// By Ythalo Rossy
// ythalorossy@gmail.com