added builder pattern

pypatterns/creational/builder.py

@@ -0,0 +1,75 @@
+from abc import ABCMeta, abstractmethod
+
+
+class Director(object, metaclass=ABCMeta):
+    """
+    Abstract director class, responsible for using a builder to fully construct an object.
+
+    Part of the builder pattern.
+    """
+    def __init__(self):
+        """
+        Initialize a new Director.
+        """
+        self.builder = None
+
+    @abstractmethod
+    def construct(self):
+        """
+        Abstract class for fully constructing an object.
+
+        Concrete implementations should override this and use a builder to construct the object.
+
+        @raise NotImplementedError: If this method is not overridden.
+        """
+        pass
+
+    def get_constructed_object(self):
+        """
+        Get the object this director is responsible for constructing.
+
+        @return: The object that this director is responsible for constructing.
+        """
+        return self.builder.constructed_object
+
+
+class Builder(object):
+    """
+    Abstract builder class, responsible for constructing various pieces of an object.
+
+    Part of the builder pattern.
+    """
+    def __init__(self, constructed_object):
+        """
+        Initialize a new Builder.
+
+        Concrete Builders should call this method from within their own __init__ method.
+        The concrete __init__ method should also register all build options to build methods,
+        by using the _register method.
+
+        @param constructed_object: An instance of an object this builder is responsible for.
+        """
+        self.constructed_object = constructed_object
+        self.build_methods = dict()
+
+    def build(self, build_option, **kwargs):
+        """
+        Build a piece of the constructed object.
+
+        @param build_option: The part of the object to build. All build options should have been registered in __init__.
+        @type build_option: str
+        @param kwargs: Additional arguments for building.
+        """
+        self.build_methods[build_option](**kwargs)
+
+    def _register(self, build_option, build_method):
+        """
+        Register a build option to a build method.
+
+        All concrete builders should call this method in their constructor at least once.
+
+        @param build_option: A string representing the part of the object to build.
+        @type build_option: str
+        @param build_method: The method to call when given build option is selected.
+        """
+        self.build_methods[build_option] = build_method

tests/creational_tests/test_builder.py

@@ -0,0 +1,146 @@
+from unittest import TestCase
+from pypatterns.creational.builder import Director, Builder
+from abc import ABCMeta, abstractmethod
+
+
+class BuilderTestCase(TestCase):
+    """
+    Unit testing class for the Builder class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Building(object):
+            def __init__(self):
+                self.floor = None
+                self.size = None
+
+            def __repr__(self):
+                return 'Floor: {0.floor} | Size: {0.size}'.format(self)
+
+        class HomeBuilder(Builder, metaclass=ABCMeta):
+
+            def __init__(self):
+                super().__init__(Building())
+                self._register('floor', self._build_floor)
+                self._register('size', self._build_size)
+
+            @abstractmethod
+            def _build_floor(self):
+                pass
+
+            @abstractmethod
+            def _build_size(self):
+                pass
+
+        class HouseBuilder(HomeBuilder):
+
+            def _build_floor(self):
+                self.constructed_object.floor = 'One'
+
+            def _build_size(self):
+                self.constructed_object.size = 'Big'
+
+        class FlatBuilder(HomeBuilder):
+
+            def _build_floor(self):
+                self.constructed_object.floor = 'More than one'
+
+            def _build_size(self):
+                self.constructed_object.size = 'Small'
+
+        self.house_builder = HouseBuilder()
+        self.flat_builder = FlatBuilder()
+
+    def test_builder(self):
+        """
+        Test the build method.
+
+        @raise AssertionError: If the test fails.
+        """
+        self.house_builder.build('floor')
+        self.house_builder.build('size')
+        self.assertEquals('One', self.house_builder.constructed_object.floor)
+        self.assertEquals('Big', self.house_builder.constructed_object.size)
+        self.assertEquals('Floor: One | Size: Big', str(self.house_builder.constructed_object))
+
+        self.flat_builder.build('floor')
+        self.flat_builder.build('size')
+        self.assertEquals('More than one', self.flat_builder.constructed_object.floor)
+        self.assertEquals('Small', self.flat_builder.constructed_object.size)
+        self.assertEquals('Floor: More than one | Size: Small', str(self.flat_builder.constructed_object))
+
+
+class DirectorTestCase(TestCase):
+    """
+    Unit testing class for the Director class
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Building(object):
+            def __init__(self):
+                self.floor = None
+                self.size = None
+
+            def __repr__(self):
+                return 'Floor: {0.floor} | Size: {0.size}'.format(self)
+
+        class HomeBuilder(Builder, metaclass=ABCMeta):
+            def __init__(self):
+                super().__init__(Building())
+                self._register('floor', self._build_floor)
+                self._register('size', self._build_size)
+
+            @abstractmethod
+            def _build_floor(self):
+                pass
+
+            @abstractmethod
+            def _build_size(self):
+                pass
+
+        class HouseBuilder(HomeBuilder):
+            def _build_floor(self):
+                self.constructed_object.floor = 'One'
+
+            def _build_size(self):
+                self.constructed_object.size = 'Big'
+
+        class FlatBuilder(HomeBuilder):
+            def _build_floor(self):
+                self.constructed_object.floor = 'More than one'
+
+            def _build_size(self):
+                self.constructed_object.size = 'Small'
+
+        class HomeDirector(Director):
+            def construct(self):
+                self.builder.build('floor')
+                self.builder.build('size')
+
+        self.house_builder = HouseBuilder()
+        self.flat_builder = FlatBuilder()
+        self.home_director = HomeDirector()
+
+    def test_construct(self):
+        """
+        Test the construct method.
+
+        @raise AssertionError: If the test fails.
+        """
+        self.home_director.builder = self.house_builder
+        self.home_director.construct()
+        house = self.home_director.get_constructed_object()
+        self.assertEquals('One', house.floor)
+        self.assertEquals('Big', house.size)
+        self.assertEquals('Floor: One | Size: Big', str(house))
+
+        self.home_director.builder = self.flat_builder
+        self.home_director.construct()
+        flat = self.home_director.get_constructed_object()
+        self.assertEquals('More than one', flat.floor)
+        self.assertEquals('Small', flat.size)
+        self.assertEquals('Floor: More than one | Size: Small', str(flat))