Store Latest Observations

[kerryrobinson]

In some use cases, the user needs to persist the last known observations for a feed on disk, so that the next time they open up the app it can be bootstrapped with all of the tracks, which are then updated as the feed connection is restored.

In the Native SDKs, this is particularly useful when using a custom DynamicEntityDataSource, because it's typically not associated with any other persisted cache/layer of the tracks. This is analogous to the KeepLatest archive which is available on an ArcGIS Stream Service. If the service author opts in to creat this archive (a feature layer) on a stream service, clients will automatically load the features from that archive (one per track / Dynamic Entity) and then consume the stream to update observations for that track.

The ability to store latest obervsions is not available in the Native SDKs, but this can be relatively easily accomplished in code by listening to the DynamicEntityDataSource DynamicEntityObservation notification events, and writing/overwriting a feature in a local mobile geodatabase as new observations come in for each Dynamic Entity. When the app is closed and then re-opened, it can first read that feature table and create new observations, then connect to the feed to update the observations.

This request has come from a customer.