Python与设计模式（二）——builder

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/foolish0421/article/details/78042981

首先看源码：

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

"""
@author: Diogenes Augusto Fernandes Herminio <[email protected]>
https://gist.github.com/420905#file_builder_python.py
"""


# Director
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()

    def build_floor(self):
        raise NotImplementedError

    def build_size(self):
        raise NotImplementedError

# 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: {0.floor} | Size: {0.size}'.format(self)


# 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)

### OUTPUT ###
# Floor: One | Size: Big
# Floor: More than One | Size: Small

大致的类图如下：

建造者类BuilderHouse和BuilderFloor都派生自建造者Builder，分贝可以生成house和floor的对象。Director中持有Builder的引用，具体是那种Builder可以有client指定。

Director的construct_building方法，会生成新的Building对象，并用对应的构建者类对building的floor和size进行初始化。