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Abstract Factory模式
提供一个共同的接口来创建相互关联的多个对象。
抽象工厂模式的用意为:给客户端提供一个接口,可以创建多个产品族中的产品对象。 不过使用抽象工厂是有条件的:
1.系统中有多个产品族,而系统一次只可能消费其中一族产品
2.同属于同一个产品族的产品在一起使用,这一约束必须在系统的设计中体现出来。
定义两个类,Dog和Cat,都拥有speak方法
class Dog(object):
def speak(self):
return "woof"
def __str__(self):
return "Dog"
class Cat(object):
def speak(self):
return "meow"
def __str__(self):
return "Cat"
写一个抽象工厂类PetShop.
class PetShop(object):
"""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()
print("We have a lovely {}".format(pet))
print("It says {}".format(pet.speak()))
初始化时,传一个Dog 或者 Cat,之后就跟普通的调用是一样的。show_pet中,初始化传入的类。
cat_shop = PetShop(Cat)
cat_shop.show_pet()
完整代码如下:
import random
class PetShop(object):
"""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()
print("We have a lovely {}".format(pet))
print("It says {}".format(pet.speak()))
class Dog(object):
def speak(self):
return "woof"
def __str__(self):
return "Dog"
class Cat(object):
def speak(self):
return "meow"
def __str__(self):
return "Cat"
# Additional factories:
# Create a random animal
def random_animal():
"""Let's be dynamic!"""
return random.choice([Dog, Cat])()
# Show pets with various factories
if __name__ == "__main__":
# A Shop that sells only cats
cat_shop = PetShop(Cat)
cat_shop.show_pet()
print("")
# A shop that sells random animals
shop = PetShop(random_animal)
for i in range(3):
shop.show_pet()
print("=" * 20)