used from an iOS app, its extensions, the Apple Watch extension or even different
apps, as long as they share some sub-state struct.</p>

<p>Some suggestions of middlewares:</p>

<ul>
<li>Run Timers, pooling some external resource or updating some local state at a constant time</li>
<li>Subscribe for <code>CoreData</code>, <code>Realm</code>, <code>Firebase Realtime Database</code> or equivalent database changes</li>
<li>Be a <code>CoreLocation</code> delegate, checking for significant location changes or b