Odoo 12 Development Cookbook - Third Edition

How to do it...

We will make a change in 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. Follow these steps to get started:

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

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

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

@api.multidef change_state(self, new_state):    for book in self:        if book.is_allowed_transition(book.state, new_state):            book.state = new_state        else:            msg = _('Moving from %s to %s is not allowed') % (book.state, new_state)            raise UserError(msg)