Abstract factory pattern

维基百科Abstract factory pattern

NOTE: 建议先阅读例子，然后阅读理论描述

Structure

Class diagram example The method createButton on the GUIFactory interface returns objects of type Button. What implementation of Button is returned depends on which implementation of GUIFactory is handling the method call.

NOTE: UML图最能够体现abstract factory pattern

Python example

from abc import ABC, abstractmethod
from sys import platform


class Button(ABC):

    @abstractmethod
    def paint(self):
        pass


class LinuxButton(Button):

    def paint(self):
        return 'Render a button in a Linux style'


class WindowsButton(Button):

    def paint(self):
        return 'Render a button in a Windows style'


class MacOSButton(Button):

    def paint(self):
        return 'Render a button in a MacOS style'


class GUIFactory(ABC):

    @abstractmethod
    def create_button(self):
        pass


class LinuxFactory(GUIFactory):

    def create_button(self):
        return LinuxButton()


class WindowsFactory(GUIFactory):

    def create_button(self):
        return WindowsButton()


class MacOSFactory(GUIFactory):

    def create_button(self):
        return MacOSButton()

def GetFactory():
    if platform == 'linux':
        factory = LinuxFactory()
    elif platform == 'darwin':
        factory = MacOSFactory()
    elif platform == 'win32':
        factory = WindowsFactory()
    else:
        raise NotImplementedError(
            'Not implemented for your platform: {}'.format(platform)
        )
    return factory
if __name__ == '__main__':
    factory = GetFactory()
    button = factory.create_button()
    result = button.paint()
    print(result)

Alternative implementation using the classes themselves as factories:

from abc import ABC, abstractmethod
from sys import platform


class Button(ABC):

    @abstractmethod
    def paint(self):
        pass


class LinuxButton(Button):
    def paint(self):
        return 'Render a button in a Linux style'


class WindowsButton(Button):

    def paint(self):
        return 'Render a button in a Windows style'


class MacOSButton(Button):

    def paint(self):
        return 'Render a button in a MacOS style'

def GetFactory():
    if platform == "linux":
        factory = LinuxButton
    elif platform == "darwin":
        factory = MacOSButton
    elif platform == "win32":
        factory = WindowsButton
    else:
        raise NotImplementedError(
            'Not implemented for your platform: {}'.format(platform)
        )

if __name__ == '__main__':
    factory = GetFactory()
    button = factory.create_button()
    result = button.paint()
    print(result)

NOTE: Everything in python is a object，so do class

下面是上述代码的UML图