The mobile service solution manages the synchronization of the offline data.

Requirements:
# Needs a form with name "offline_data"
# The form offline_data needs a method ws_read(version,name)
# If the data shown in mobile app is user specific the form offline_data needs a method ws_authenticate(useruid,password)
# The mobile_service and rest_ws plugin to be installed

By default Servoy will load the first 200 pks when a form is used. This is not needed in the service solution and can be prevented by calling databaseManager.setCreateEmptyFormFoundsets() in the solution onopen global method:
{code}
function onSolutionOpen() {
	// prevent prefilling of form foundsets with default query
	databaseManager.setCreateEmptyFormFoundsets()
}
{code}

h3. Constructing a offline data package for the mobile client

The ws_read(version,name) on the offline_data form has to return an OfflineDataDescription (=JSON) object filled with foundset data the developer wants the mobile client to retrieve.
An OfflineDataDescription instance is created with:
{code}
var retval = plugins.mobileservice.createOfflineDataDescription('data_');
{code}
Note: the argument is optional and is used to call rest endpoints for row data at forms starting with this prefix

Then we need to provide a list of relation names which should be used in traversal to find all data, like:
{code}
var traverse = new Array();
traverse.push('accountmanager_to_companies');
traverse.push('companies_to_contacts');
{code}

Lastly we have instruct the OfflineDataDescription to collect the data, starting with root foundset (containing records) and return.
{code}
retval.addFoundSet(fs_contact, traverse);
return retval;
{code}
Basically addFoundSet in the service solution exposes an unrelated foundset to the mobile client, which can be used in an unrelated way like in a (first) form or databaseManager.getFoundset(...)
For each record in the provided (unrelated) foundset the specified relations are traversed and all data taken.

h3. User specific data

In order to provide a mobile client with user specific data the ws_authenticate(useruid,password) method should be added:
{code}
function ws_authenticate(useruid,password)
{
	//TODO find user and check password against pwhash column
	if (password == 'demo')//static demo check
	{
		var retval = new Object();
		retval.username = useruid;
		return retval;
	}
	return false;
}
{code}

In the ws_read method we can utilize the authenticate username variable via
{code}
var authenticate_info = questionParams.ws_authenticate[0];
globals.username = authenticate_info.username;
{code}
Here the authenticate username is put into a global variable which in turn can be used like:
{code}
//prepare personal data
var fs_contact = globals.contact_data$username;//global related foundset using username global var, containing the account manager contact
{code}

Full ws_read method for personalized data.
{code}
function ws_read(version,name)
{
	var questionParams = arguments[arguments.length-1];

	//create return value
	var retval = plugins.mobileservice.createOfflineDataDescription('data_');

	//setting the key for user_select relation
	var authenticate_info = questionParams.ws_authenticate[0];
	globals.username = authenticate_info.username;

	//prepare personal data
	var fs_contact = globals.contact_data$username;//global related foundset using username global var, containing the account manager contact

	/**
	 * @type {Array<String>}
	 */
	var traverse = new Array();
	traverse.push('accountmanager_to_companies');
	traverse.push('companies_to_contacts');

	retval.addFoundSet(fs_contact, traverse);
	return retval;
}
{code}

h3. Providing/retrieving entity(=table) row data

Row/record data is retrieved in separate calls for each entity, for example for "orders" row data results in a call to "orders" form is made on ws_read method.
Note: If a prefix is provided in the offlinedata the call will end up at prefix+entityname, example for prefix "data_" the call happens on form "data_orders"

ws_read is with a list of pks it wants as row data for, example code:
{code}
function ws_read(version,method)
{
	var questionParams = arguments[arguments.length-1];

	if (method == 'list')
	{
		/**
		 * @type {String}
		 */
		var ids = questionParams.ids[0];
		if (ids != null && ids != '')
		{
			var idsa = ids.split(',', -1);
			if (idsa.length > 0)
			{
				var json = plugins.mobileservice.getRowDescriptions(foundset.getDataSource(), idsa)
				return json;
			}
		}
	}

	throw 404;
}
{code}
TIP: since ws_read for entities is likely the same, it might be beneficial to create a base form containing this logic and extend from this form

h3. Syncing back the changes from the mobile client

ws_update is called for changes made by mobile client, example code:
{code}
function ws_update(data,version,pk)
{
	if (foundset.find())
	{
		foundset.contact_id = pk;
		var count = foundset.search();
		if (count > 0)
		{
			var rec = foundset.getRecord(1);
			databaseManager.copyMatchingFields(data,rec,true);
			databaseManager.saveData(rec);
		}
	}
}
{code}

ws_create is called for new records on the mobile client, example code:
{code}
function ws_create(data,version,pk)
{
	var rec = foundset.getRecord(foundset.newRecord());

	databaseManager.copyMatchingFields(data,rec,true);
	databaseManager.saveData(rec);

}
{code}
Note: the retrieved PK (and derived FK's) is always UUID's if the underlaying datamodel is not UUID based, keep and apply a mapping\!

ws_delete is called for deleted record in the mobile client, example code:

{code}
function ws_delete(version,pk)
{
   if (foundset.find())
   {
     var table = databaseManager.getTable(controller.getDataSource());
     var pkname = table.getRowIdentifierColumnNames()[0]
     foundset[pkname] = pk;
     var count = foundset.search();
     if (count > 0)
     {
       var rec = foundset.getRecord(1);
       foundset.deleteRecord(rec);
     }
   }
}
{code}

h5. Transaction based syncing

By default the mobile client will do a rest call per changed row, these are separated calls so every call will be on a fresh new client on the serverside.

Because of this a transaction can't be used for all the changes of 1 mobile client and then fail a sync when something goes wrong. If the sync should be in 1 call, so that a transaction can be used over all the calls to the above ws_update/ws_create/ws_delete methods, a ws_update method must be created on the offline_data form.

This ws_update method then gets a full data package of all the changes that a mobile client has, this will then be dispatched over all the methods that are described above.

An example of a ws_update method on the offline_data form:

{code}
function ws_update(data,version,authenticateResult)
{
	try {
		databaseManager.startTransaction();
		plugins.mobileservice.performSync(data,version,authenticateResult);
		databaseManager.commitTransaction();
	} catch (e) {
		databaseManager.rollbackTransaction();
		// log the error and return false to that the mobile client will know the sync did fail.
		application.output(e,LOGGINGLEVEL.ERROR);
		return false;
	}
}
{code}



This code above starts a transaction then calls the performSync method of the mobile service plugin. This plugin will dispatch all the changes to the various ws_update/create/delete methods of the entity forms. If something goes wrong then an exception will be thrown and the transaction will rollback.

h5. Other pages

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