【编程思想】【设计模式】【创建模式creational】抽象工厂模式abstract_factory

Python版

https://github.com/faif/python-patterns/blob/master/creational/abstract_factory.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
*What is this pattern about?

In Java and other languages, the Abstract Factory Pattern serves to provide an interface for
creating related/dependent objects without need to specify their
actual class.
>>在Java和其他语言中，抽象工厂模式为创建相关联的对象提供借口，而不用制定他们的实体类

The idea is to abstract the creation of objects depending on business
logic, platform choice, etc.
>>这是为了抽象创建基于业务逻辑和用户选择而创建的

In Python, the interface we use is simply a callable, which is "builtin" interface
in Python, and in normal circumstances we can simply use the class itself as
that callable, because classes are first class objects in Python.
>>在python中，我们使用的接口是可调用的，是一个可创建的借口
>>在python中，通常情况下，我们只使用类本身作为可调用的接口，因为类是第一个对象

*What does this example do?
This particular implementation abstracts the creation of a pet and
does so depending on the factory we chose (Dog or Cat, or random_animal)
This works because both Dog/Cat and random_animal respect a common
interface (callable for creation and .speak()).
>>这个抽象的实现了创造一个宠物，然后基于我们选择的工厂类型（狗或者猫或者其他随意的动物）
>>这个可以实现因为猫，狗或者其他的动物都遵照这个接口（可调用创造和说话）
Now my application can create pets abstractly and decide later,
based on my own criteria, dogs over cats.
>>现在我的应用可以抽象创造宠物然后再根据我个人的准早来创造狗，而不是猫

*Where is the pattern used practically?

*References:
https://sourcemaking.com/design_patterns/abstract_factory
http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/

*TL;DR80
Provides a way to encapsulate a group of individual factories.
"""

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)

### OUTPUT ###
# We have a lovely Cat
# It says meow
# 
# We have a lovely Dog
# It says woof
# ====================
# We have a lovely Cat
# It says meow
# ====================
# We have a lovely Cat
# It says meow
# ====================