Observe Example¶

#------------------------------------------------------------------------------
# Copyright (c) 2013, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#------------------------------------------------------------------------------
""" Demonstrate the observe behavior of Atom objects.

<< autodoc-me >>
"""
from __future__ import print_function

from atom.api import Atom, Unicode, Range, Typed, observe


class Dog(Atom):

    name = Unicode()


class Person(Atom):
    """ A simple class representing a person object.

    """
    name = Unicode()

    age = Range(low=0)

    dog = Typed(Dog, ())

    def _observe_age(self, change):
        print('Age changed: {0}'.format(change['value']))

    @observe('name')
    def any_name_i_want(self, change):
        print('Name changed: {0}'.format(change['value']))

    @observe('dog.name')
    def another_random_name(self, change):
        print('Dog name changed: {0}'.format(change['value']))


def main():
    bob = Person(name='Robert Paulson', age=40)
    bob.name = 'Bobby Paulson'
    bob.age = 50
    bob.dog.name = 'Scruffy'

    def watcher_func(change):
        print('Watcher func change: {0}'.format(change['value']))

    bob.observe('age', watcher_func)
    bob.age = 51
    bob.unobserve('age', watcher_func)
    bob.age = 52  # No call to watcher func


if __name__ == '__main__':
    main()

Age changed: 40
Name changed: Robert Paulson
Name changed: Bobby Paulson
Age changed: 50
Dog name changed: Scruffy
Age changed: 51
Watcher func change: 51
Age changed: 52