Preparing Soups for Mobile Sync

Soups that exchange information with the Salesforce cloud typically use Mobile Sync for synchronization. To support Mobile Sync, most app types require you to create and manage special soup fields for “sync up” operations.

Types of apps that require you to code these special fields include:

Hybrid apps that do not use Force.SObject (from mobilesync.js) to create and manage local records
Native apps
React Native apps

If your hybrid app uses Force.SObject for local records, Mobile Sync automatically creates and manages these fields for you. You can ignore the rest of this discussion.

Add the following fields to your soup elements. Be sure to set the appropriate field to true for every create, update, or delete operation. The first three are operation type fields:
__locally_created__
- Type: string
- Set this field to true on elements that your app creates locally.
__locally_updated__
- Type: string
- Set this field to true after your app updates an element locally.
__locally_deleted__
- Type: string
- Set this field to true when your app is deleting an element locally.
The other fields to add are control fields:
__local__
- Type: string
- This field indicates that some local change has occurred. You’re required to:
  - Set this field to true when any of the operation type fields is true.
  - Add a string index spec on this field.
__sync_id__
- Type: integer
- This field ensures that the cleanResyncGhosts() method removes only the desired soup elements. Mobile Sync manages the content of this field for you.
Add a soup index for each of the operation and control fields. See Registering Soups with Configuration Files.

During sync up operations, Mobile Sync looks for soup elements with __local__ set to true. For each match, it evaluates the operation type fields and then performs the operation indicated by the following precedence hierarchy.

Precedence	Field	If set to true...
1 (highest)	`__locally_deleted__`	`__locally_created__` and `__locally_updated__` flags are ignored. Mobile Sync deletes the local record and, if it exists, the server record. If the server record does not exist, no remote action occurs.
2	`__locally_created__`	`__locally_updated__` flag is ignored. If `__locally_deleted__` is not true, Mobile Sync creates the record on the server.
3	`__locally_updated__`	Ignored if either `__locally_deleted__` or `__locally_created__` is true. Otherwise, Mobile Sync writes the updated record to the server.

Finally, Mobile Sync resets all four fields to false.

The following examples are taken from the various language versions of the MobileSyncExplorer sample app.

iOS Native

This Objective-C example sets system fields by sending updateSoupForFieldName:fieldValue: messages to an SObjectData object. Using SFMobileSyncSyncManager constants for the field names, it sets the __local__ and __locally_created__ fields before upserting the new element. You can find the SObjectData definition in the iOS sample app.

Android Native

The following Java example handles created and updated elements, but not deletions. It calls the JSONObject put() method to create and initialize the system fields, using SyncManager constants for the field names. After the fields are properly assigned, it either creates or upserts the element based on the isCreate control flag.

Hybrid with the Mobile Sync Plug-in and React Native

The following React Native code can easily be adapted for hybrid apps that use the Mobile Sync plug-in. This example shows how to update and delete—or undelete—a contact. The onSaveContact() function marks the record as updated, sets __local__ to true, and then saves the changes. The onDeleteUndeleteContact() function flips the __locally_deleted__ field. It then sets the __local__ field to match the operation type value and saves the changes.

The storeMgr object is defined in the sample project as a wrapper around SmartStore and the Mobile Sync plug-in. Its saveContact() function accepts a contact object and a callback, and upserts the contact into the soup. The callback shown here calls navigator.pop(), which is specific to React Native. Hybrid apps can replace the saveContact() function with any code that calls the SmartStore upsert() function.