Async Module

Helper utils for Orange GUI programming.

Provides asynchronous() decorator for making methods calls in async mode. Once method is decorated it will have task.on_start(), task.on_result() and task.callback() decorators for callbacks wrapping.

• on_start must take no arguments
• on_result must accept one argument (the result)
• callback can accept any arguments

For instance:

class Widget(QObject):
    def __init__(self, name):
        super().__init__()
        self.name = name

    @asynchronous
    def task(self):
        for i in range(3):
            time.sleep(0.5)
            self.report_progress(i)
        return 'Done'

    @task.on_start
    def report_start(self):
        print('`{}` started'.format(self.name))

    @task.on_result
    def report_result(self, result):
        print('`{}` result: {}'.format(self.name, result))

    @task.callback
    def report_progress(self, i):
        print('`{}` progress: {}'.format(self.name, i))

Calling an asynchronous method will launch a daemon thread:

first = Widget(name='First')
first.task()
second = Widget(name='Second')
second.task()

first.task.join()
second.task.join()

A possible output:

`First` started
`Second` started
`Second` progress: 0
`First` progress: 0
`First` progress: 1
`Second` progress: 1
`First` progress: 2
`First` result: Done
`Second` progress: 2
`Second` result: Done

In order to terminate a thread either call stop() method or raise StopExecution exception within task():

first.task.stop()