CloudServices/Sync/FxSync/Developer/ClientAPI

Writing an Engine class

Your Engine class serves to tie together your Store, Tracker, and Record classes into a bundle that the Weave sync algorithm can instantiate and use.

You're probably sick of writing subclasses by this point, but don't worry: this one is very easy. I saved it for last because it requires the least code.

Your class must derive from the {{{SyncEngine}}} class, defined in {{{weave/modules/engines.js}}}. {{{SyncEngine}}} contains a lot of code which handles logic for the core sync algorithm, but your subclass won't need to call any of this directly, unless you are overriding part of the sync algorithm to provide custom sync behavior (an advanced technique outside the scope of this article).

A sample Engine class:

const EXPORTED_SYMBOLS = ["FooEngine"];

const Cu = Components.utils;

Cu.import("resource://weave/engines.js");

function FooEngine() {
  this._init(); 
}
FooEngine.prototype = {
  __proto__: SyncEngine.prototype,
  name: "foo",
  displayName: "Foo",
  logName: "Foo",
  _storeObj: FooStore,
  _trackerObj: FooTracker
};

As you can see, there isn't actually any new code here at all; the prototype simply defines some metadata such as the Store and Tracker classes to use, and the human-readable name that will be used in the log files to identify errors and status messages coming from this engine.