Signals (event hooking)

Flask Applications that want to be kept informed about certain actions that took place in the underlying Flask-User extensions can do so by subscribing ‘signals’ to receive event notification.

Flask-User defines the following signals:

# Signal                    # Sent when ...
user_changed_password       # a user changed their password
user_changed_username       # a user changed their username
user_confirmed_email        # a user confirmed their email
user_forgot_password        # a user submitted a reset password request
user_logged_in              # a user logged in
user_logged_out             # a user logged out
user_registered             # a user registered for a new account
user_reset_password         # a user reset their password (forgot password)

See the http://flask.pocoo.org/docs/signals/

Installing Blinker – REQUIRED!

NB: Flask-User relies on Flask signals, which relies on the ‘blinker’ package. Event notification WILL NOT WORK without first installing the ‘blinker’ package.

pip install blinker

See http://pythonhosted.org/blinker/

Subscribing to Signals

AFTER BLINKER HAS BEEN INSTALLED, An application can receive event notifications by using the event signal’s connect_via() decorator:

from flask_user import user_logged_in

@user_logged_in.connect_via(app)
def _after_login_hook(sender, user, **extra):
    sender.logger.info('user logged in')

For all Flask-User event signals:

- sender points to the app, and

- user points to the user that is associated with this event.

See Subscribing to signals

Troubleshooting

If the code looks right, but the tracking functions are not called, make sure to check to see if the ‘blinker’ package has been installed (analyze the output of pip freeze).