设计模式- 创建型模式， 建造者模式(2)

java23种设计模式之一，英文叫Builder Pattern。其核心思想是将一个“复杂对象的构建算法”与它的“部件及组装方式”分离，使得构件算法和组装方式可以独立应对变化；复用同样的构建算法可以创建不同的表示，不同的构建过程可以复用相同的部件组装方式。

# coding: utf-8

from enum import Enum
import time

PizzaProgress = Enum('PizzaProgress', 'queued preparation baking ready')
PizzaDough = Enum('PizzaDough', 'thin thick')
PizzaSauce = Enum('PizzaSauce', 'tomato creme_fraiche')
PizzaTopping = Enum('PizzaTopping', 'mozzarella double_mozzarella bacon ham mushrooms red_onion oregano')
STEP_DELAY = 3          # 考虑是示例，单位为秒


class Pizza:

    def __init__(self, name):
        self.name = name
        self.dough = None
        self.sauce = None
        self.topping = []

    def __str__(self):
        return self.name

    def prepare_dough(self, dough):
        self.dough = dough
        print('preparing the {} dough of your {}...'.format(self.dough.name, self))
        time.sleep(STEP_DELAY)
        print('done with the {} dough'.format(self.dough.name))


class MargaritaBuilder:

    def __init__(self):
        self.pizza = Pizza('margarita')
        self.progress = PizzaProgress.queued
        self.baking_time = 5        # 考虑是示例，单位为秒

    def prepare_dough(self):
        self.progress = PizzaProgress.preparation
        self.pizza.prepare_dough(PizzaDough.thin)

    def add_sauce(self):
        print('adding the tomato sauce to your margarita...')
        self.pizza.sauce = PizzaSauce.tomato
        time.sleep(STEP_DELAY)
        print('done with the tomato sauce')

    def add_topping(self):
        print('adding the topping (double mozzarella, oregano) to your margarita')
        self.pizza.topping.append([i for i in
                                   (PizzaTopping.double_mozzarella, PizzaTopping.oregano)])
        time.sleep(STEP_DELAY)
        print('done with the topping (double mozzarrella, oregano)')

    def bake(self):
        self.progress = PizzaProgress.baking
        print('baking your margarita for {} seconds'.format(self.baking_time))
        time.sleep(self.baking_time)
        self.progress = PizzaProgress.ready
        print('your margarita is ready')


class CreamyBaconBuilder:

    def __init__(self):
        self.pizza = Pizza('creamy bacon')
        self.progress = PizzaProgress.queued
        self.baking_time = 7        # 考虑是示例，单位为秒

    def prepare_dough(self):
        self.progress = PizzaProgress.preparation
        self.pizza.prepare_dough(PizzaDough.thick)

    def add_sauce(self):
        print('adding the crème fraîche sauce to your creamy bacon')
        self.pizza.sauce = PizzaSauce.creme_fraiche
        time.sleep(STEP_DELAY)
        print('done with the crème fraîche sauce')

    def add_topping(self):
        print('adding the topping (mozzarella, bacon, ham, mushrooms, red onion, oregano) to your creamy bacon')
        self.pizza.topping.append([t for t in
                                   (PizzaTopping.mozzarella, PizzaTopping.bacon,
                                    PizzaTopping.ham, PizzaTopping.mushrooms,
                                    PizzaTopping.red_onion, PizzaTopping.oregano)])
        time.sleep(STEP_DELAY)
        print('done with the topping (mozzarella, bacon, ham, mushrooms, red onion, oregano)')

    def bake(self):
        self.progress = PizzaProgress.baking
        print('baking your creamy bacon for {} seconds'.format(self.baking_time))
        time.sleep(self.baking_time)
        self.progress = PizzaProgress.ready
        print('your creamy bacon is ready')


class Waiter:

    def __init__(self):
        self.builder = None      ## 实例属性最好写在__init__里面，哪怕属性不是在初始化时候绑定或者建立，也有写个None，声明一下属性，否则直接在普通方法生成一个实例属性，不符合pycharm的pep8。

    def construct_pizza(self, builder):
        self.builder = builder
        [step() for step in (builder.prepare_dough,
                             builder.add_sauce, builder.add_topping, builder.bake)]

    @property
    def pizza(self):
        return self.builder.pizza


def validate_style(builders):
    try:
        pizza_style = input('What pizza would you like, [m]argarita or [c]reamy bacon? ')
        builder = builders[pizza_style]()
        valid_input = True
    except KeyError as err:
        print('Sorry, only margarita (key m) and creamy bacon (key c) are available')
        return (False, None)
    return (True, builder)


def main():
    builders = dict(m=MargaritaBuilder, c=CreamyBaconBuilder)
    valid_input = False
    while not valid_input:
        valid_input, builder = validate_style(builders)
    print()
    waiter = Waiter()
    waiter.construct_pizza(builder)
    pizza = waiter.pizza
    print()
    print('Enjoy your {}!'.format(pizza))

if __name__ == '__main__':
    main()

看代码先从main函数看起，不是从上往下一行行看，通过。

 waiter在其他例子中通常也会叫director。例如下面。一个产品类，通过把不同的构建者传给导演类创造不同属性的产品对象。

class Director(object):
    def __init__(self):
        self.builder = None
 
    def construct_building(self):
        self.builder.new_building()
        self.builder.build_floor()
        self.builder.build_size()
 
    def get_building(self):
        return self.builder.building
 
 
# Abstract Builder
class Builder(object):
    def __init__(self):
        self.building = None
 
    def new_building(self):
        self.building = Building()
 
 
# Concrete Builder
class BuilderHouse(Builder):
    def build_floor(self):
        self.building.floor = 'One'
 
    def build_size(self):
        self.building.size = 'Big'
 
 
class BuilderFlat(Builder):
    def build_floor(self):
        self.building.floor = 'More than One'
 
    def build_size(self):
        self.building.size = 'Small'
 
 
# Product
class Building(object):
    def __init__(self):
        self.floor = None
        self.size = None
 
    def __repr__(self):
        return 'Floor: %s | Size: %s' % (self.floor, self.size)
 
 
# Client
if __name__ == "__main__":
    director = Director()
    director.builder = BuilderHouse()
    director.construct_building()
    building = director.get_building()
    print(building)
    director.builder = BuilderFlat()
    director.construct_building()
    building = director.get_building()
    print(building)