Python: Factory Method Pattern

 

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193

# Python 3.9 # 工厂方法模式 Factory Method Pattern   from __future__ import annotations from abc import ABC, abstractmethod import pygame  # pip install pygame -i https://pypi.tuna.tsinghua.edu.cn/simple     class Shape(object):     def __init__(self, x, y):         self.x = x         self.y = y       def draw(self):         raise NotImplementedError()       def move(self, direction):         if direction == 'up':             self.y -= 4         elif direction == 'down':             self.y += 4         elif direction == 'left':             self.x -= 4         elif direction == 'right':             self.x += 4       @staticmethod     def factory(shape_type, pos_x, pos_y):         if shape_type == 'Circle':             return Circle(pos_x, pos_y)         if shape_type == 'Square':             return Square(pos_x, pos_y)         assert 0, "Bad shape requested:" + type     class Square(Shape):     def __init__(self, x, y):         if x < 0:             x = 0         elif x > 780:             x = 780         if y < 0:             y = 0         elif y > 580:             y = 580         super(Square, self).__init__(x,y)       def draw(self):         pygame.draw.rect(             screen,             (255, 255, 0),             pygame.Rect(self.x, self.y, 20, 20)         )       def move(self, direction):         if direction == 'up' and self.y > 0:             super(Square, self).move('up')         elif direction == 'down' and self.y < 580:             super(Square, self).move('down')         elif direction == 'left' and self.x > 0:             super(Square, self).move('left')         elif direction == 'right' and self.x < 780:             super(Square, self).move('right')     class Circle(Shape):     def __init__(self, x, y):         if x < 10:             x = 10         elif x > 790:             x = 790         if y < 10:             y = 10         elif y > 590:             y = 590         super(Circle, self).__init__(x, y)       def draw(self):         pygame.draw.circle(             screen,             (0, 255, 255),             (self.x, self.y),             10         )       def move(self, direction):         if direction == 'up' and self.y > 10:             super(Circle, self).move('up')         elif direction == 'down' and self.y < 590:             super(Circle, self).move('down')         elif direction == 'left' and self.x > 10:             super(Circle, self).move('left')         elif direction == 'right' and self.x < 790:             super(Circle, self).move('right')       class Creator(ABC):     """     The Creator class declares the factory method that is supposed to return an     object of a Product class. The Creator's subclasses usually provide the     implementation of this method.     """       @abstractmethod     def factory_method(self):         """         Note that the Creator may also provide some default implementation of         the factory method.         """         pass       def some_operation(self) -> str:         """         Also note that, despite its name, the Creator's primary responsibility         is not creating products. Usually, it contains some core business logic         that relies on Product objects, returned by the factory method.         Subclasses can indirectly change that business logic by overriding the         factory method and returning a different type of product from it.         """           # Call the factory method to create a Product object.         product = self.factory_method()           # Now, use the product.         result = f"Creator: The same creator's code has just worked with {product.operation()}"           return result     """ Concrete Creators override the factory method in order to change the resulting product's type. """     class ConcreteCreator1(Creator):     """     Note that the signature of the method still uses the abstract product type,     even though the concrete product is actually returned from the method. This     way the Creator can stay independent of concrete product classes.     """       def factory_method(self) -> Product:         return ConcreteProduct1()     class ConcreteCreator2(Creator):     def factory_method(self) -> Product:         return ConcreteProduct2()     class Product(ABC):     """     The Product interface declares the operations that all concrete products     must implement.     """       @abstractmethod     def operation(self) -> str:         pass     """ Concrete Products provide various implementations of the Product interface. """     class ConcreteProduct1(Product):     def operation(self) -> str:         return "{Result of the ConcreteProduct1}"     class ConcreteProduct2(Product):     def operation(self) -> str:         return "{Result of the ConcreteProduct2}"     def client_code(creator: Creator) -> None:     """     The client code works with an instance of a concrete creator, albeit through     its base interface. As long as the client keeps working with the creator via     the base interface, you can pass it any creator's subclass.     """       print(f"Client: I'm not aware of the creator's class, but it still works.\n"           f"{creator.some_operation()}", end="")       def print_hi(name):     # Use a breakpoint in the code line below to debug your script.     print(f'Hi, {name}')  # Press Ctrl+F8 to toggle the breakpoint.

　　

　

调用：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

# 调用 工厂方法模式 Factory Method Pattern # Press the green button in the gutter to run the script. if __name__ == '__main__':     print_hi('geovindu')     window_dimensions = 800, 600         print("App: Launched with the ConcreteCreator1.")     client_code(ConcreteCreator1())     print("\n")       print("App: Launched with the ConcreteCreator2.")     client_code(ConcreteCreator2())       window_dimensions = 800, 600     screen = pygame.display.set_mode(window_dimensions)       obj = Shape.factory('Square', 100, 100)       player_quits = False       while not player_quits:         for event in pygame.event.get():             if event.type == pygame.QUIT:                 player_quits = True               pressed = pygame.key.get_pressed()             if pressed[pygame.K_c]:                 obj = Shape.factory('Circle', obj.x, obj.y)             if pressed[pygame.K_s]:                 obj = Shape.factory('Square', obj.x, obj.y)             if pressed[pygame.K_UP]:                 obj.move('up')             if pressed[pygame.K_DOWN]:                 obj.move('down')             if pressed[pygame.K_LEFT]:                 obj.move('left')             if pressed[pygame.K_RIGHT]:                 obj.move('right')               screen.fill((0, 0, 0))             obj.draw()         pygame.display.flip()

 

输出：

 

 

?

1 2 3 4 5 6 7 8 9

Hi, geovindu App: Launched with the ConcreteCreator1. Client: I'm not aware of the creator's class, but it still works. Creator: The same creator's code has just worked with {Result of the ConcreteProduct1}   App: Launched with the ConcreteCreator2. Client: I'm not aware of the creator's class, but it still works. Creator: The same creator's code has just worked with {Result of the ConcreteProduct2} Process finished with exit code 0