MobX Quick Start Guide

Lazy loading the temperature

Let's take an example where we will lazy load the temperature for a city, but only when it is accessed. This can be done by modeling the observable property with the hooks for onBecomeObserved() and onBecomeUnobserved(). The following snippet shows this in action:

// A mock service to simulate a network call to a weather APIconst temperatureService = {    fetch(location) {        console.log('Invoked temperature-fetch');        return new Promise(resolve =>            setTimeout(resolve(Math.round(Math.random() * 35)), 200),        );    },};class City {    @observable temperature;    @observable location;    interval;    disposers;    constructor(location) {        this.location = location;        const disposer1 = onBecomeObserved(            this,            'temperature',            this.onActivated, ); ...