Builder（建造者）

意图：

将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。

适用性：

当创建复杂对象的算法应该独立于该对象的组成部分以及它们的装配方式时。

当构造过程必须允许被构造的对象有不同的表示时。

#!/usr/bin/python
#coding:utf8

"""
    Builder
"""

# 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()

# 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)