工厂模式形式
- 工厂方法：对不同的输入参数返回不同对象;
- 抽象工厂：是一组用于创建一系列相关事物对象的工厂方法。
工厂方法
数据来源形式：
- 人们可读文件：XML、Atom、YAML、JSON等
- 二进制文件：.sq3、.mp3
问题：
- 有一些数据存储在XML和JSON文件中，对这两个文件进行解析，获取一些信息;
- 对这些外部服务进行集中式的客户端连接。
数据形式：
- JSON
[
{
"id": "0001",
"type": "donut",
"name": "Cake",
"ppu": 0.55,
"batters": {
"batter": [
{
"id": "1001",
"type": "Regular"
},
{
"id": "1002",
"type": "Chocolate"
},
{
"id": "1003",
"type": "Blueberry"
},
{
"id": "1004",
"type": "Devil's Food"
}
]
},
"topping": [
{
"id": "5001",
"type": "None"
},
{
"id": "5002",
"type": "Glazed"
},
{
"id": "5005",
"type": "Sugar"
},
{
"id": "5007",
"type": "Powdered Sugar"
},
{
"id": "5006",
"type": "Chocolate with Sprinkles"
},
{
"id": "5003",
"type": "Chocolate"
},
{
"id": "5004",
"type": "Maple"
}
]
},
{
"id": "0002",
"type": "donut",
"name": "Raised",
"ppu": 0.55,
"batters": {
"batter": [
{
"id": "1001",
"type": "Regular"
}
]
},
"topping": [
{
"id": "5001",
"type": "None"
},
{
"id": "5002",
"type": "Glazed"
},
{
"id": "5005",
"type": "Sugar"
},
{
"id": "5003",
"type": "Chocolate"
},
{
"id": "5004",
"type": "Maple"
}
]
},
{
"id": "0003",
"type": "donut",
"name": "Old Fashioned",
"ppu": 0.55,
"batters": {
"batter": [
{
"id": "1001",
"type": "Regular"
},
{
"id": "1002",
"type": "Chocolate"
}
]
},
"topping": [
{
"id": "5001",
"type": "None"
},
{
"id": "5002",
"type": "Glazed"
},
{
"id": "5003",
"type": "Chocolate"
},
{
"id": "5004",
"type": "Maple"
}
]
}
]- XML
<persons>
<person>
<firstName>John</firstName>
<lastName>Smith</lastName>
<age>25</age>
<address>
<streetAddress>21 2nd Street</streetAddress>
<city>New York</city>
<state>NY</state>
<postalCode>10021</postalCode>
</address>
<phoneNumbers>
<phoneNumber type="home">212 555-1234</phoneNumber>
<phoneNumber type="fax">646 555-4567</phoneNumber>
</phoneNumbers>
<gender>
<type>male</type>
</gender>
</person>
<person>
<firstName>Jimy</firstName>
<lastName>Liar</lastName>
<age>19</age>
<address>
<streetAddress>18 2nd Street</streetAddress>
<city>New York</city>
<state>NY</state>
<postalCode>10021</postalCode>
</address>
<phoneNumbers>
<phoneNumber type="home">212 555-1234</phoneNumber>
</phoneNumbers>
<gender>
<type>male</type>
</gender>
</person>
<person>
<firstName>Patty</firstName>
<lastName>Liar</lastName>
<age>20</age>
<address>
<streetAddress>18 2nd Street</streetAddress>
<city>New York</city>
<state>NY</state>
<postalCode>10021</postalCode>
</address>
<phoneNumbers>
<phoneNumber type="home">212 555-1234</phoneNumber>
<phoneNumber type="mobile">001 452-8819</phoneNumber>
</phoneNumbers>
<gender>
<type>female</type>
</gender>
</person>
</persons>实现
import xml.etree.ElementTree as etree#导入python自带库，用来处理XML
import json#处理JSON
class JSONConnector:#类JSONConnector解析JSON文件
def __init__(self, filepath):
self.data = dict()
with open(filepath, mode='r', encoding='utf-8') as f:
self.data = json.load(f)
@property
def parsed_data(self):
return self.data
class XMLConnector:#类XMLConnector解析XML文件
def __init__(self, filepath):
self.tree = etree.parse(filepath)
@property
def parsed_data(self):
return self.tree
def connection_factory(filepath):#工厂方法，基于输入文件路径的扩展名返回一个JSONConnector或XMLConnector的实例
if filepath.endswith('json'):
connector = JSONConnector
elif filepath.endswith('xml'):
connector = XMLConnector
else:
raise ValueError('Cannot connect to {}'.format(filepath))
return connector(filepath)
def connect_to(filepath):
factory = None
try:
factory = connection_factory(filepath)
except ValueError as ve:
print(ve)
return factory
def main():
sqlite_factory = connect_to('/home/spark/下载/mpdp-code-master/chapter1/data/person.sq3')#确认异常处理是否有效，应返回“Cannot connect to /home/spark/下载/mpdp-code-master/chapter1/data/person.sq3
”
print()
xml_factory = connect_to('/home/spark/下载/mpdp-code-master/chapter1/data/person.xml')
xml_data = xml_factory.parsed_data
liars = xml_data.findall(".//{}[{}='{}']".format('person',
'lastName', 'Liar'))
print('found: {} persons'.format(len(liars)))
for liar in liars:
print('first name: {}'.format(liar.find('firstName').text))
print('last name: {}'.format(liar.find('lastName').text))
[print('phone number ({})'.format(p.attrib['type']),
p.text) for p in liar.find('phoneNumbers')]
print()
json_factory = connect_to('/home/spark/下载/mpdp-code-master/chapter1/data/donut.json')
json_data = json_factory.parsed_data
print('found: {} donuts'.format(len(json_data)))
for donut in json_data:
print('name: {}'.format(donut['name']))
print('price: ${}'.format(donut['ppu']))
[print('topping: {} {}'.format(t['id'], t['type'])) for t in donut['topping']]
if __name__ == '__main__':
main()输出
Cannot connect to /home/spark/下载/mpdp-code-master/chapter1/data/person.sq3
found: 2 persons
first name: Jimy
last name: Liar
phone number (home) 212 555-1234
first name: Patty
last name: Liar
phone number (home) 212 555-1234
phone number (mobile) 001 452-8819
found: 3 donuts
name: Cake
price: $0.55
topping: 5001 None
topping: 5002 Glazed
topping: 5005 Sugar
topping: 5007 Powdered Sugar
topping: 5006 Chocolate with Sprinkles
topping: 5003 Chocolate
topping: 5004 Maple
name: Raised
price: $0.55
topping: 5001 None
topping: 5002 Glazed
topping: 5005 Sugar
topping: 5003 Chocolate
topping: 5004 Maple
name: Old Fashioned
price: $0.55
topping: 5001 None
topping: 5002 Glazed
topping: 5003 Chocolate
topping: 5004 Maple
抽象工厂
问题
- 创造一个游戏。至少包含两个游戏，一个面向孩子，一个面向成人;
- 在运行时，基于用户输入，决定该创建哪个游戏并运行。
实现
class Frog:
def __init__(self, name):
self.name = name
def __str__(self):
return self.name
def interact_with(self, obstacle):
print('{} the Frog encounters {} and {}!'.format(self,
obstacle, obstacle.action()))
class Bug:
def __str__(self):
return 'a bug'
def action(self):
return 'eats it'
class FrogWorld:
def __init__(self, name):
print(self)
self.player_name = name
def __str__(self):
return '\n\n\t------ Frog World ———'
def make_character(self):
return Frog(self.player_name)
def make_obstacle(self):
return Bug()
class Wizard:
def __init__(self, name):
self.name = name
def __str__(self):
return self.name
def interact_with(self, obstacle):
print('{} the Wizard battles against {} and {}!'.format(self, obstacle, obstacle.action()))
class Ork:
def __str__(self):
return 'an evil ork'
def action(self):
return 'kills it'
class WizardWorld:
def __init__(self, name):
print(self)
self.player_name = name
def __str__(self):
return '\n\n\t------ Wizard World ———'
def make_character(self):
return Wizard(self.player_name)
def make_obstacle(self):
return Ork()
class GameEnvironment:
def __init__(self, factory):
self.hero = factory.make_character()
self.obstacle = factory.make_obstacle()
def play(self):
self.hero.interact_with(self.obstacle)
def validate_age(name):
try:
age = input('Welcome {}. How old are you? '.format(name))
age = int(age)
except ValueError as err:
print("Age {} is invalid, please try \
again…".format(age))
return (False, age)
return (True, age)
def main():
name = input("Hello. What's your name? ")
valid_input = False
while not valid_input:
valid_input, age = validate_age(name)
game = FrogWorld if age < 18 else WizardWorld
environment = GameEnvironment(game(name))
environment.play()
if __name__ == '__main__':
main()输出
Hello. What's your name? du
Welcome du. How old are you? 10
------ Frog World ———
du the Frog encounters a bug and eats it!
----------
Hello. What's your name? du
Welcome du. How old are you? 20
------ Wizard World ———
du the Wizard battles against an evil ork and kills it!
总结
两种模式都可以应用于一下场景：
- 想要追踪对象的创建时;
- 想要将对象的创建与应用解耦时;
- 想要优化应用的性能和资源占用时。
工厂方法设计模式的实现，是一个不属于任何类的单一函数，负责单一种类对象的创建；抽象工厂设计模式的实现，是同属于单个类的许多个工厂方法用于创建一系列种类的相关对象。
