编程思想设计模式创建模式creational抽象工厂模式abstract_factory

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Python版

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

 

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#!/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
# ====================
Python转载版

 

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