Tracked property notify API strawman

index.js

import Timer from 'simple-timer';
import Component from '@glimmer/component';
import {  } from '@glimmer/tracking';

export default class TimerComponent extends Component {
  constructor() {
    // Mark the timer as "untracked" (i.e., we're asserting
    // that timer contains no interior tracked properties at all).
    // This function gives us back the timer as well as a callback
    // function to call when any interior mutation may have occurred.
    const [timer, timerDidChange] = notify(new Timer());

    this.timer = timer;
    this.timer.onTick(() => {
      // invalidate timer and any nested properties used in a template
      timerDidChange();
    });
  }

  @tracked
  get currentSeconds() {
    return this.timer.seconds;
  }

  @tracked
  get currentMinutes() {
    return this.timer.minutes;
  }
}