Base Handler

Last updated: 17 Jan 2025

The BaseHandler is the simplest of all handlers. Specify which events you are interested in, then provide the code to execute when one of those events is emitted. All the handlers inherit from BaseHandler, and many of yours will too.

Handling Events With BaseHandler #

To create a class that responds to one or more events, inherit from BaseHandler, set the RESPONDS_TO constant, and implement the compute() method.

from canvas_sdk.events import EventType
from canvas_sdk.handlers.base import BaseHandler

class MyEventHandler(BaseHandler):

    RESPONDS_TO = EventType.Name(EventType.TASK_CREATED)

    def compute(self):
        # Your code goes here!
        return []

You can respond to one event, or several. To respond to multiple events, set RESPONDS_TO to a list of event types.

# Respond when tasks are created:
RESPONDS_TO = EventType.Name(EventType.TASK_CREATED)

# Respond when tasks are created OR updated:
RESPONDS_TO = [
    EventType.Name(EventType.TASK_CREATED),
    EventType.Name(EventType.TASK_UPDATED),
]

The compute() method must return a list of Effects. That list can be empty, of course. You have access to event information with self.event, self.target, andself.context, as well as configuration information for your plugin with self.secrets. You can use our Data Module to retrieve additional information at runtime.