Implemented Memento design pattern.

pypatterns/structural/memento.py

@@ -0,0 +1,41 @@
+from copy import deepcopy
+
+
+class Memento(object):
+    """
+    Memento class as part of the Memento design pattern.
+    """
+    def __init__(self, state):
+        """
+        Initialize a new Memento instance.
+
+        @param state: The state to save in this Memento.
+        @type state: dict
+        """
+        self.__state = state
+
+    @property
+    def state(self):
+        return self.__state
+
+
+class Originator(object):
+    """
+    Originator base class as part of the Memento design pattern.
+    """
+    def commit(self):
+        """
+        Commit this objects state to a memento.
+
+        @return: A memento instance with this objects state.
+        """
+        return Memento(deepcopy(self.__dict__))
+
+    def rollback(self, memento):
+        """
+        Rollback this objects state to a previous state.
+
+        @param memento: The memento object holding the state to rollback to.
+        @type memento: Memento
+        """
+        self.__dict__ = memento.state

tests/structural_tests/test_memento.py

@@ -0,0 +1,64 @@
+from unittest import TestCase
+from pypatterns.structural.memento import Memento, Originator
+
+
+class MementoTestCase(TestCase):
+    """
+    Unit testing class for the Memento Class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        self.state = {'foo': 'bar'}
+
+    def test_init(self):
+        """
+        Test the __init__ method.
+
+        @raise AssertionError: If the test fails.
+        """
+        memento = Memento(self.state)
+
+        self.assertEqual(memento.state, self.state)
+
+
+class OriginatorTestCase(TestCase):
+    """
+    Unit testing class for the Originator class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Cat(Originator):
+
+            def __init__(self, name):
+                self.name = name
+
+        self.cat_class = Cat
+
+    def test_commit(self):
+        """
+        Test the commit method.
+
+        @raise AssertionError: If the test fails.
+        """
+        cat = self.cat_class('Tom')
+        cat_memento = cat.commit()
+
+        self.assertDictEqual(cat.__dict__, cat_memento.state)
+
+    def test_rollback(self):
+        """
+        Test the rollback method.
+
+        @raise AssertionError: If the test fails.
+        """
+        cat = self.cat_class('Tom')
+        cat_memento = cat.commit()
+
+        cat.name = 'jerry'
+        cat.rollback(cat_memento)
+
+        self.assertEqual('Tom', cat.name)