python设计模式-享元设计模式，抽象工厂设计模式，面向对象设计模式

news2024/11/25 22:47:14

享元设计模式

享元(flyweight)设计模式属于结构设计模式类别。它提供了一种减少对象数的方法。它包含各种有助于改进应用程序结构的功能。享元对象最重要的特性是不可变的。这意味着一旦构建就不能修改它们。该模式使用HashMap来存储引用对象

如何实现享元(flyweight)设计模式？

以下程序演示如何实现享元模式

class ComplexGenetics(object):
   def __init__(self):
      pass

   def genes(self, gene_code):
      return "ComplexPatter[%s]TooHugeinSize" % (gene_code)
class Families(object):
   family = {}

   def __new__(cls, name, family_id):
      try:
         id = cls.family[family_id]
      except KeyError:
         id = object.__new__(cls)
         cls.family[family_id] = id
      return id

   def set_genetic_info(self, genetic_info):
      cg = ComplexGenetics()
      self.genetic_info = cg.genes(genetic_info)

   def get_genetic_info(self):
      return (self.genetic_info)

def test():
   data = (('a', 1, 'ATAG'), ('a', 2, 'AAGT'), ('b', 1, 'ATAG'))
   family_objects = []
   for i in data:
      obj = Families(i[0], i[1])
      obj.set_genetic_info(i[2])
      family_objects.append(obj)

   for i in family_objects:
      print "id = " + str(id(i))
      print i.get_genetic_info()
   print "similar id's says that they are same objects "

if __name__ == '__main__':
   test()

执行上述程序生成以下输出
在这里插入图片描述

抽象工厂设计模式

抽象工厂模式也被称为工厂的工厂。此设计模式属于创建设计模式类别。它提供了创建对象的最佳方法之一。
它包含一个接口，负责创建与工厂相关的对象。

如何实现抽象工厂模式？

参考以下程序，演示如何实现抽象工厂模式。

class Window:
   __toolkit = ""
   __purpose = ""

   def __init__(self, toolkit, purpose):
      self.__toolkit = toolkit
      self.__purpose = purpose

   def getToolkit(self):
      return self.__toolkit

   def getType(self):
      return self.__purpose

class GtkToolboxWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "ToolboxWindow")

class GtkLayersWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "LayersWindow")

class GtkMainWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "MainWindow")

class QtToolboxWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "ToolboxWindow")

class QtLayersWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "LayersWindow")

class QtMainWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "MainWindow")

# Abstract factory class
class UIFactory:
   def getToolboxWindow(self): pass
   def getLayersWindow(self): pass
   def getMainWindow(self): pass

class GtkUIFactory(UIFactory):
   def getToolboxWindow(self):
      return GtkToolboxWindow()
   def getLayersWindow(self):
      return GtkLayersWindow()
   def getMainWindow(self):
      return GtkMainWindow()

class QtUIFactory(UIFactory):
   def getToolboxWindow(self):
      return QtToolboxWindow()
   def getLayersWindow(self):
      return QtLayersWindow()
   def getMainWindow(self):
      return QtMainWindow()

if __name__ == "__main__":
   gnome = True
   kde = not gnome

   if gnome:
      ui = GtkUIFactory()
   elif kde:
      ui = QtUIFactory()

   toolbox = ui.getToolboxWindow()
   layers = ui.getLayersWindow()
   main = ui.getMainWindow()

   print "%s:%s" % (toolbox.getToolkit(), toolbox.getType())
   print "%s:%s" % (layers.getToolkit(), layers.getType())
   print "%s:%s" % (main.getToolkit(), main.getType())

执行上面示例代码，得到以下结果 -
在这里插入图片描述

说明

在上面的程序中，抽象工厂为每个窗口创建对象。它调用每个方法，按预期执行输出。

面向对象设计模式

面向对象的模式是最常用的模式。几乎所有的编程语言都可以找到这种模式。

如何实现面向对象的模式？

下面让我们看看如何实现面向对象的模式。
参考以下实现代码 -

class Parrot:
   # class attribute
   species = "bird"

   # instance attribute
   def __init__(self, name, age):
      self.name = name
      self.age = age

# instantiate the Parrot class
blu = Parrot("Blu", 10)
woo = Parrot("Woo", 15)

# access the class attributes
print("Blu is a {}".format(blu.__class__.species))
print("Woo is also a {}".format(woo.__class__.species))

# access the instance attributes
print("{} is {} years old".format( blu.name, blu.age))
print("{} is {} years old".format( woo.name, woo.age))