如何制作Python工厂类 [英] How to make a Python factory class

问题描述

我希望能够基于枚举类创建对象，并使用字典.像这样:

I want to be able to create objects based on an enumeration class, and use a dictionary. Something like this:

class IngredientType(Enum):
    SPAM        = auto() # Some spam
    BAKE_BEANS  = auto() # Baked beans
    EGG         = auto() # Fried egg

class Ingredient(object):
    pass    
class Spam(Ingredient):
    pass
class BakedBeans(Ingredient):
    pass
class Egg(Ingredient):
    pass


class IngredientFactory(object):
    """Factory makes ingredients"""

    choice = {
        IngredientType.SPAM: IngredientFactory.MakeSpam,
        IngredientType.BAKED_BEANS: IngredientFactory.MakeBakedBeans,
        IngredientType.EGG: IngredientFactory.MakeEgg
    }

    @staticmethod
    def make(type):
        method = choice[type]
        return method()

    @staticmethod
    def makeSpam():
        return Spam()

    @staticmethod
    def makeBakedBeans():
        return BakedBeans()

    @staticmethod
    def makeEgg():
        return Egg()

但是我得到了错误:

NameError: name 'IngredientFactory' is not defined

由于某些原因，无法创建字典.我在哪里错了?

For some reason the dictionary can't be created. Where am I going wrong here?

推荐答案

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这使用户可以从枚举中选择类类型，并阻止任何其他类型.这也意味着用户不太可能写出带有拼写错误的坏字符串".他们只是使用枚举.测试的输出如下:

This gets the user to select a class type from the enumeration, and blocks any other type. It also means user's are less likely to write 'bad strings' with spelling mistakes. They just use the enums. The output from the test is then, something like this:

Circle.draw
Circle.erase
Circle.draw
Circle.erase
Square.draw
Square.erase
Square.draw
Square.erase
Circle.draw
Circle.erase
Circle.draw
Circle.erase
Square.draw
Square.erase

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