Reporting errors to the user

During method execution, it is sometimes necessary to abort processing because the action that's requested by the user isn't valid or an error condition has been met. This recipe shows you how to manage these cases by showing a helpful error message.

Getting ready

This recipe assumes that you have an instance ready, with the my_library add-on module available, as described in the previous recipe.

How to do it...

We will make a change to the change_state method from the previous recipe and display a helpful message when the user is trying to change the state that is not allowed by the is_allowed_transition method. Perform the following steps to get started:

1. Add the following import at the beginning of the Python file:

   from odoo.exceptions import UserError
   from odoo.tools.translate import _

2. Modify the change_state method and raise a UserError exception from the else part:

   def change_state(self, new_state):
      ...