chrisrowtcliff / mobile-app-documentdb-offlinesync-sample

This is a proof of concept project where we tight up a DocumentDB instance with complex (nested) types with several SQLite mobile clients using Azure Mobile Apps with Offline Sync.

Azure Mobile Apps using DocumentDb + Incremental and offline sync

This is a proof of concept project where we tight up a DocumentDB instance with complex (nested) types with several SQLite mobile clients using Azure Mobile Apps with Offline Sync. In this project we are trying to achieve following features:

• Accessing data from DocumentDB on mobile clients through Azure Mobile Apps
• Ability for mobile clients to work with downloaded data in offline mode
• Incremental sync on client to download only updated/added/data (limits the data transfer)
• Support for flat DocumentDB objects
• Support for more complex nested objects

Key points:

• Custom DomainManager for TableController - it allows us to sync data on client through Azure Mobile Apps Tables to work with DocumentDB objects
• Azure Mobile Apps client SDK with offline sync configuration uses "createdAt" and "updatedAt" attributes to determine which objects needs to be synced. THESE ARE CASE SENSITIVE!! We learned it the hard way...
• At this point of time (16.01.2017), Azure Mobile Apps client SDK offline sync feature works only for flat objects. It's not suitable for more complex and nested types
• Best we could achieve was to implement offline sync for level 1 nested objects similar to this:

{
 "text": "Mew task ios",
 "nested": {
   "nestedText": "144 J B Hazra Road",
   "nestedBool": "false"
 },
 "nestedItems": [
   {
     "nestedText": "xxoxoxoxoxox",
     "nestedBool": "true"
   }
 ],
 "complete": true,
 "id": "8d16700a-fcc0-4453-b740-e3eef8c0c340",
 "version": null,
 "createdat": "2017-01-11T12:27:24.1394782+00:00",
 "updatedat": "2017-01-11T14:24:03.4335527+00:00",
 "deleted": false
}

Unfortunately, nested objects/collections can only be stored as strings/JSON in SQLite store on mobile client:

We achieved this by implementing a custom Expand attribute to include nested objects when sending data from Azure Mobile App to client. We used it in our TableController here