Qt - WebKit - Promise implementation

drive.js

_promises = [];
promise_success = function(uid, result) {
  if (_promises[uid] == undefined || _promises[uid]._success_callback == undefined) {
    return;
  }
  _promises[uid]._success_callback(result);
  delete _promises[uid];
}
promise_error = function(uid, err) {
  if (_promises[uid] == undefined || _promises[uid]._error_callback == undefined) {
    return;
  }
  _promises[uid]._error_callback(err);
  delete _promises[uid];
}
when = function(result) {
  return {
    then: function(callback, error_callback) {
      if (result && result['_promise_success'] !== undefined && result['_promise_error'] !== undefined) {
        uid = result['_promise_uid']();
        if (_promises[uid] == undefined) {
          console.log("set the promises for " + uid);
          _promises[uid] = self
        }
        _promises[uid]._success_callback = callback;
        _promises[uid]._error_callback = error_callback;
        result._promise_success.connect(promise_success);
        result._promise_error.connect(promise_error);
        result.start();
      } else {
        callback(result);
      }
    }
  };
}

// Usage of the Promise

when( drive.update_password_async(uid, password) ).then(
		function (res) {
			if (res == "") {
				$scope.update_password_error = null;
				$scope.engines = this.getEngines();
				// Waiting for better solution
				top.location.reload();
			} else {
				$scope.update_password_error = res;
				$scope.password = "";
			}
			$scope.currentAction = "";
			$scope.$apply();
		}
	);

drive_api.py

class Api(QObject)
  ...
  @QtCore.pyqtSlot(str, str, result=str)
  def update_password(self, uid, password):
    return self._update_password(uid, password)
  ...

class Promise(Worker):
  _promise_success = QtCore.pyqtSignal(str, str)
  _promise_error = QtCore.pyqtSignal(str, str)

  def __init__(self, runner, *args, **kwargs):
    self._uid = uuid.uuid1().hex
    self._runner = runner
    self._kwargs = kwargs
    self._args = args
    super(Promise, self).__init__(name="Promise_" + self._uid)
    self._result = None

  @QtCore.pyqtSlot(result=str)
  def _promise_uid(self):
    return self._uid

  @QtCore.pyqtSlot()
  def start(self):
    self._thread.started.connect(self.run)
    self._thread.start()

  def _execute(self):
    try:
      result = self._runner(*self._args, **self._kwargs)
      self._promise_success.emit(self._uid, result)
    except Exception as e:
      self._promise_error.emit(self._uid, repr(e))

drive_api_final.py

class Api(QObject)
  # ...
  @QtCore.pyqtSlot(str, str, result=str)
  def update_password(self, uid, password):
    return self._update_password(uid, password)

  @QtCore.pyqtSlot(str, str, result=QtCore.QObject)
  def update_password_async(self, uid, password):
    return Promise(self._update_password, uid, password)
  # ...

class PromiseWrapper(QtCore.QObject):
  def __init__(self, promise):
    super(PromiseWrapper, self).__init__()
    self._promise = promise

  @QtCore.pyqtSlot()
  def run(self):
    self._promise.run()

class Promise(Worker):
  _promise_success = QtCore.pyqtSignal(str, str)
  _promise_error = QtCore.pyqtSignal(str, str)

  def __init__(self, runner, *args, **kwargs):
    self._uid = uuid.uuid1().hex
    self._runner = runner
    self._kwargs = kwargs
    self._args = args
    super(Promise, self).__init__(name="Promise_" + self._uid)
    self._result = None
    self._wrapper = PromiseWrapper(self)
    self._wrapper.moveToThread(self._thread)

  def moveToThread(self, QThread):
    # Prevent this object to be move to other threads
    pass

  @QtCore.pyqtSlot(result=str)
  def _promise_uid(self):
    return self._uid

  @QtCore.pyqtSlot()
  def start(self):
    self._thread.started.connect(self._wrapper.run)
    self._thread.start()

  def _execute(self):
    try:
      result = self._runner(*self._args, **self._kwargs)
      self._promise_success.emit(self._uid, result)
    except Exception as e:
      self._promise_error.emit(self._uid, repr(e))

Thanks for the examples. But how should the Worker class look like? Just like this one: https://github.com/nuxeo/nuxeo-drive/blob/0737527b7d75d5c5b5e6047e5e6c01e0c9f6548e/nuxeo-drive-client/nxdrive/engine/workers.py#L26 ?