Multiple Observers not working on singular State machine

[MKhibkin1]

• Python State Machine version:
• Python version:
• Operating System:

Description

I would like to have multiple observers responding to an event from a statemachine.

What I Did

from statemachine import StateMachine, State


class MyObs(object):

    def __init__(self):
        pass

    def on_move_car(self):
        print("I observed moving from 1")
        return self

class MyObs2(object):
    def __init__(self):
        pass

    def on_move_car(self):
        print("I observed moving from 2")
        return self

class Car(StateMachine):
    def __init__(self):
        super().__init__()

    stopped = State(initial=True)
    moving = State()

    move_car = stopped.to(moving)
    stop_car = moving.to(stopped)

    @move_car.on
    def on_move_car(self):
        print("Im moving")


if __name__ == "__main__":

    car = Car()
    obs = MyObs()
    obs2 = MyObs2()
    car.add_observer(obs)
    car.add_observer(obs2)

    car.move_car()

I would expect to see both "I observed moving from 1" and "I observed moving from 2" but it seems the first observer to encounter the event will swallow the callback.

[fgmacedo]

Hi @MKhibkin1 , I was able to reproduce the issue. Thanks for reporting this.

The problem is that I've implemented an "unique" by name on the callback registry. I use the callback name to know if a callback is already registered.

Here I check if the callback is already in the list:

python-statemachine/statemachine/callbacks.py

Lines 147 to 148 in c60f7fe

	if func in self.items:
	return

And here is how I compare two distinct callbacks (by it's name):

python-statemachine/statemachine/callbacks.py

Lines 29 to 30 in c60f7fe

	def __eq__(self, other):
	return self.func == getattr(other, "func", other)

I'm thinking about using a qualified name to the callback, including a identification of the observer, so even with multiple observers we still get unique names.

[cmutzel]

@fgmacedo - I am really loving your library and excited to see this issue fixed. It looks like you haven't created a release since doing so? Is there a way I could help you to do the release - would like to get this fix.

[fgmacedo]

Hi @cmutzel, thanks for your kind words. I was waiting to deliver a more significant release. But let's release what we already have implemented.

[fgmacedo]

New version 2.1.0 released! 🎉

https://python-statemachine.readthedocs.io/en/latest/releases/2.1.0.html