pyqgis - Usage of QgsTask and QgsTaskManager

I'm trying to test the new QgsTask and QgsTaskManager, I found some examples in the PullRequest in github. I modified it slightly and added a print(i) in the code bellow:

from qgis.core import QgsTask, QgsTaskManager
from time import sleep
import random
def run1(task,time):
   wait_time = time / 100.0
   sum = 0
   iterations = 0
   for i in range(101):
       sleep(wait_time)

       print(i)
        # use task.setProgress to report progress
        task.setProgress( i )
        sum += random.randint(0,100)
        iterations += 1
        # check task.isCancelled() to handle cancellation
        if task.isCancelled():
            stopped()
            return
        # raise expections to abort task

        #if random.randint(0,100) == 7:
        #    raise Exception('bad value!')
    # use task object to store results of calculations or operations
    task.result = [sum,iterations]

task=QgsTask.fromFunction('waste cpu', run1, 2)
mgr=QgsTaskManager()
mgr.addTask(task)
task.isFinished()

When I run this code in the Python console it returns 0 two times and then nothing more. I expected 101 printouts (0-100)? Afterwards I tried to see if it was finished with trying to call task.isFinished(), hence that gave me a RuntimeError: wrapped C/C++ object of type QgsTaskWrapper has been deleted.

In the end I would like use one QgsTask to run a time consuming script and one QgsTask to run a dialog (maybe a progressbar) telling the user that script is still running..

Any suggestion what I'm doing/thinking wrong or were to look at other examples?

EDIT: The problem was not only that there was two "L" in isCancel and start of QgsTaskManager, it was also that I tried to use print() within QgsTask. So I tried another approach with two GUIs that I tried in this repo.

EDIT: I updated the github Master repo using a QtTimer, still no 100% success, hence the branch without QgsTask is working as expected. But I really want to understand how QgsTask is to be implemented..

Answer

I kind of made it :) I can run this once, hence when I tries to do it a second time it fails and I need to print(1) in run_counting. The project is uploaded to https://github.com/axelande/QgisTest

def run_counting(self):
    counting = int(self.dlg.LESeconds.text())
    counting_test = CountingTest()

    task1 = QgsTask.fromFunction('counting', counting_test.run_count,
                                 counting,
                                 on_finished=self.stop_from_counting)
    waiting_msg = WaitingMsg()
    task2 = QgsTask.fromFunction('waiting', waiting_msg.run)
    self.tsk_mngr.addTask(task1)
    print(1) #This is required but I don't know why?
    self.tsk_mngr.addTask(task2)

The classes CountingTest and WaitingMsg requires a sleep that is longer than the QtTimer timer.

class WaitingMsg(QtWidgets.QDialog, FORM_CLASS):
    def __init__(self, parent=None):
        """Constructor."""
        super(WaitingMsg, self).__init__(parent)
        self.setupUi(self)
        self.cancel_is_set = False
        self.task = None
        self.my_timer = None

    def set_cancel(self):

        if self.task.isCanceled():
            self.done(0)

    def run(self, task):
        self.task = task
        self.show()
        self.my_timer = QtCore.QTimer(self)
        self.my_timer.timeout.connect(self.set_cancel)
        self.my_timer.start(500)  # 1 sec intervall
        sleep(.6)

        self.exec_()
        self.done(0)

class CountingTest(QtWidgets.QDialog, FORM_CLASS):
    def __init__(self, parent=None):
        """Constructor."""
        super(CountingTest, self).__init__(parent)
        self.setupUi(self)
        self.my_timer = None
        self.task = None

        self.counting = None
        self.t0 = None

    def _update_text(self):
        tid = int(time() - self.t0)
        self.LSeconds.setText(str(tid))
        self.update()
        if tid == self.counting:
            self.done(0)
            return self.counting


    def run_count(self, task, counting):
        self.counting = int(counting)
        print(counting)
        self.t0 = time()
        self.task = task
        self.show()
        self.my_timer = QtCore.QTimer(self)
        self.my_timer.timeout.connect(self._update_text)
        self.my_timer.start(1000)  # 1 sec interval

        sleep(1.1)
        self.exec_()
        self.done(0)
        return counting