工廠方法

使用相同的介面，來處理不同的事情。

在工廠設計模式中，客戶端可以請求一個物件，無需知道這個物件來自哪裡（使用具體的哪個類來生成的，使用者只是呼叫同一個方法就能實現）

工廠通常有兩種形式，

一種是工廠方法

一種是抽象工廠

以下 是工廠方法的程式碼

使用者通過connect_to這個方法，來生成一個物件，獲取xml或者json資料，而無需關心其他細節。

data目錄下

donut.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"
            }
        ]
    }
]
 

data目錄下

person.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>
 

工廠模式程式碼

factory_method.py

import xml.etree.ElementTree as etree
import json


class JSONConnector:

    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:

    def __init__(self, filepath):
        self.tree = etree.parse(filepath)

    @property
    def parsed_data(self):
        return self.tree


def connection_factory(filepath):
    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('data/person.sq3')
    print()

    xml_factory = connect_to('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('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()