OneShot class

[dlech]

(followup to #487)

Since Pybricks is currently poll-based rather than event-based (i.e. we check if a button is currently pressed rather than having button state changed event), it would be useful to have a OneShot class to help detect changes in state.

it might look something like this:

from pybricks.pupdevices import Remote
from pybricks.parameters import Button
from pybricks.tools import wait

# Connect to the remote.
my_remote = Remote()

# global program state
state = {
    "gear_angle": 0
}

class OneShot:
    def __init__(self, callback):
        """
        Args:
            callback: a callable that will be invoked when the one-shot is triggered.
        """
        self.callback = callback
        self.state = False

    def set(self):
        """
        If the one-shot was already triggered, does nothing, otherwise triggers
        the oneshot and calls the callback.
        """
        if not self.state:
            self.state = True
            callback()

    def reset(self):
        """
        Resets the one-shot trigger.
        """
        self.state = False

def shift_gears(delta):
    # TODO: add check to ensure new gear_angle is in range
    state["gear_angle"] += delta


gear_up = OneShot(lambda: shift_gears(90))
gear_down = OneShot(lambda: shift_gears(-90))

while True:
    pressed = my_remote.buttons.pressed()

    if Button.LEFT in pressed:
        gear_up.set()
    else:
        gear_up.reset()

    if Button.RIGHT in pressed:
        gear_down.set()
    else:
        gear_down.reset()

    wait(10)

[laurensvalk]

I like it.

This could be a good fit for pybricks.tools.