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# (C) Copyright 2005-2023 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" Test whether HasTraits objects with cycles can be garbage collected.
"""
# Standard library imports
import unittest
# Enthought library imports
from traits.api import HasTraits, Instance, Int
class TestCase(unittest.TestCase):
""" Tests the 'target' argument for on_traits_change. """
def test_simple(self):
""" Tests a simple dynamic trait change handler. """
class Test(HasTraits):
i = Int
# Create objects
obj = Test()
target = HasTraits()
# Set up to count changes in i
self.count = 0
def count_notifies():
self.count += 1
obj.on_trait_change(count_notifies, "i", target=target)
# Change the trait
obj.i = 10
# Delete the target and change it again
del target
obj.i = 0
# The count should be 1
self.assertEqual(self.count, 1)
def test_extended(self):
""" Tests a dynamic trait change handler using extended names. """
class Child(HasTraits):
i = Int
class Parent(HasTraits):
child = Instance(Child)
# Create objects
parent = Parent(child=Child())
target = HasTraits()
# Set up to count changes in i
self.count = 0
def count_notifies():
self.count += 1
parent.on_trait_change(count_notifies, "child:i", target=target)
# Change the trait
parent.child.i = 10
# Delete the target and change it again
del target
parent.child.i = 0
# The count should be 1
self.assertEqual(self.count, 1)
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