Realm: Notification after initial sync

Question

According to the docs Realm can notify you when certain actions are taking place like "every time a write transaction is committed". I am using the Realm Object Server and the first time a user opens my app a large set of data is synched from the server down to the app. I would like to show a loading screen and not present the main UI of my app until Realm has completed its initial sync. Is there a way to be notified / determine when this process is complete?

Answer 1

The realm.io website just posted documentation on how to do this.

Asynchronously Opening Realms

If opening a Realm might require a time-consuming operation, such as applying migrations or downloading the remote contents of a synchronized Realm, you should use the openAsync API to perform all work needed to get the Realm to a usable state on a background thread before dispatching to the given queue. You should also use openAsync with Realms that are set read-only.

For example:

Realm.openAsync({
  schema: [PersonSchema],
  schemaVersion: 42,
  migration: function(oldRealm, newRealm) {
    // perform migration (see "Migrations" in docs)
  }
}, (error, realm) => {
  if (error) {
    return;
  }
  // do things with the realm object returned by openAsync to the callback
  console.log(realm);
})

The openAsync command takes a configuration object as its first parameter and a callback as its second; the callback function receives a boolean error flag and the opened Realm.

Initial Downloads

In some cases, you might not want to open a Realm until it has all remote data available. In such a case, use openAsync. When used with a synchronized Realm, this will download all of the Realm’s contents before the callback is invoked.

var carRealm;
Realm.openAsync({
  schema: [CarSchema],
  sync: {
    user: user,
    url: 'realm://object-server-url:9080/~/cars'
  }
}, (error, realm) => {
  if (error) {
    return;
  }
  // Realm is now downloaded and ready for use
  carRealm = realm;
});