意图:
提供一个创建一系列相关或相互依赖对象的接口,而无需指定它们具体的类。
适用性:
一个系统要独立于它的产品的创建、组合和表示时。
一个系统要由多个产品系列中的一个来配置时。
当你要强调一系列相关的产品对象的设计以便进行联合使用时。
当你提供一个产品类库,而只想显示它们的接口而不是实现时。
#!/usr/bin/python #coding:utf8 ''' Abstract Factory ''' import random class PetShop: """A pet shop""" def __init__(self, animal_factory=None): """pet_factory is our abstract factory. We can set it at will.""" self.pet_factory = animal_factory def show_pet(self): """Creates and shows a pet using the abstract factory""" pet = self.pet_factory.get_pet() print("This is a lovely", str(pet)) print("It says", pet.speak()) print("It eats", self.pet_factory.get_food()) # Stuff that our factory makes class Dog: def speak(self): return "woof" def __str__(self): return "Dog" class Cat: def speak(self): return "meow" def __str__(self): return "Cat" # Factory classes class DogFactory: def get_pet(self): return Dog() def get_food(self): return "dog food" class CatFactory: def get_pet(self): return Cat() def get_food(self): return "cat food" # Create the proper family def get_factory(): """Let's be dynamic!""" return random.choice([DogFactory, CatFactory])() # Show pets with various factories if __name__ == "__main__": shop = PetShop() for i in range(3): shop.pet_factory = get_factory() shop.show_pet() print("=" * 20)