Events

Introduction

Events allow you to run functions in parallel by using event objects. Instead of calling functions or threads one after another, events let you register functions and then trigger them all at once. Each registered function runs in its own thread, so your robot can do multiple things—like blinking lights and driving—at the same time.

In order to create and then use an Event, follow these steps in order:

1. Create the event with Event.

2. Register a function to trigger when the Event is broadcast using event.

3. Broadcast an Event:

   • broadcast – Triggers all registered functions in an event object to run concurrently.

   • broadcast_and_wait – Triggers all registered functions in an event object and waits for them to finish before continuing.

Create an Event

Event creates an event object that manages function execution in separate threads.

Usage:
Event()

Parameter	Description
	This constructor has no parameters.

def move_square():
    for index in range(4):
        drivetrain.drive_for(FORWARD, 150)
        drivetrain.turn_for(RIGHT, 90)

# *** Creating the move_event Event ***
move_event = Event()

# Register move_square to move_event
move_event(move_square)

# Call all functions registered to move_event
move_event.broadcast()

Register Functions to an Event

When you register a function to an event, it will execute in a separate thread when the event is broadcasted.

Usage:
event(callback, args)

Parameter	Description
event	The name of the previously created event object.
callback	A function that is previously defined to execute when the event is broadcasted.
args	Optional. A tuple containing arguments to pass to the callback function. See Using Functions with Parameters for more information.

def move_square():
    for index in range(4):
        drivetrain.drive_for(FORWARD, 150)
        drivetrain.turn_for(RIGHT, 90)

# Creating the move_event Event
move_event = Event()

# *** Register move_square to move_event ***
move_event(move_square)

# Call all functions registered to move_event
move_event.broadcast()

Broadcast an Event

broadcast

broadcast triggers an event, starting all registered functions in separate threads. This method does not pause execution of any subsequent functions.

Usage:
event.broadcast()

Parameter	Description
event	The name of the previously created event object.

# Build Used: Super Code Base 2.0
def move_square():
    for index in range(4):
        drivetrain.drive_for(FORWARD, 150)
        drivetrain.turn_for(RIGHT, 90)

move_event = Event()
move_event(move_square)
# Broadcasting the move_event Event
move_event.broadcast()
optical_sensor.set_light_power(100, PERCENT)

broadcast_and_wait

broadcast_and_wait starts an event but waits for all registered functions to finish before continuing with subsequent functions.

Usage:
event.broadcast_and_wait()

Parameter	Description
event	The name of the previously created event object.

def move_square():
    for index in range(4):
        drivetrain.drive_for(FORWARD, 150)
        drivetrain.turn_for(RIGHT, 90)

# Set up and call the move_square event
move_event = Event()
move_event(move_square)
# Broadcast the move_event Event and wait
move_event.broadcast_and_wait()
optical_sensor.set_light_power(100, PERCENT)