Part 7: Other Changes¶
When the app does not work as expected, the user should know what is happening with the app. FreedomBox framework provides an API for running and showing diagnostics results. Most of the common diagnostic tests are implemented by the framework as part of the components used by an app. FreedomBox takes care of calling the diagnostics method and displaying the list in a formatted manner.
To implement additional diagnostic tests on top of those provided by the
framework, the method
plinth.app.App.diagnose() has to be overridden or in
a component that belongs to the app, the method
plinth.app.Component.diagnose() has to be overridden. The methods must
return a list in which each item is the result of a test performed. The item
itself is a two-tuple containing the display name of the test followed by the
class TransmissionAppView(views.AppView): ... def diagnose(): """Run diagnostics and return the results.""" results = super().diagnose() results.append(['Example test', 'passed']) return results
The user can trigger the diagnostics test by going to System -> Diagnostics
page. This runs diagnostics for all the applications. Users can also run
diagnostics specifically for this app from the app’s page. A diagnostics menu
item is shown by the
plinth.views.AppView and app.html template
diagnose() method is overridden in the app or a
Sometimes we may feel the need to write some debug messages to the console and system logs. Doing this in FreedomBox is just like doing this any other Python application.
import logging logger = logging.getLogger(__name__) def example_method(): logger.debug('A debug level message') logger.info('Showing application page - %s', request.method) try: something() except Exception as exception: # Print stack trace logger.exception('Encountered an exception - %s', exception)
For more information see Python logging framework documentation.
Every string message that is visible to the user must be localized to user’s native language. For this to happen, our app needs to be internationalized. This requires marking the user visible messages for translation. FreedomBox apps use the Django’s localization methods to make that happen.
from django.utils.translation import gettext_lazy as _ class TransmissionApp(app_module.App): ... def __init__(self): ... info = app_module.Info(... name=_('Transmission'), ... short_description=_('BitTorrent Web Client'), ...)
Notice that the app’s name, description, etc. are wrapped in the
call. This needs to be done for the rest of our app. We use the
gettext_lazy in some cases and we use the
gettext in other cases. This is
because in the second case the
is made once and reused for every user looking at the interface. These users may
each have a different language set for their interface. Lookup made for one
language for a user should not be used for other users. The
provided by Django makes sure that the return value is an object that will
actually be converted to string at the final moment when the string is being
displayed. In the first case, the lookup is made and string is returned
All of this is the usual way internationalization is done in Django. See Internationalization and localization documentation for more information.