Chapter 3: Responding to events

Now that our Extension is connected to our dashboard, let’s use an event handler to respond to when user selects a mark on the dashboard.

Tip

An event handler is a method that is called whenever an event occurs, for example, when the user makes a selection on the dashboard. You can create an event handler using the register_event_handler method from Anvil X.

In the code pane for Main, create and register the event handler using the following code (changes highlighted).

from ._anvil_designer import MainTemplate
from anvil import *
from anvil.tables import app_tables
from anvil import tableau

from trexjacket.api import get_dashboard
dashboard = get_dashboard()

class Main(MainTemplate):
  def __init__(self, **properties):
    self.init_components(**properties)
    dashboard.register_event_handler('selection_changed', self.selection_changed_event_handler)

  def selection_changed_event_handler(self, event):
    user_selection = event.worksheet.get_selected_marks()
    print(f"Got a selected record: {user_selection}, with length: ({len(user_selection)})")

register_event_handler takes 2 arguments:

1. The kind of event we want to respond to ('selection_changed' in this case)

2. The method that will execute when the event occurs (self.selection_changed_event_handler)

Now that we’ve created and registered our event handler, let’s test it out! Reload your extension in Tableau and click on a state. Return to the Anvil IDE and see the output in the “Tableau Output 1” pane (see gif).