61 lines
1.5 KiB
Python
61 lines
1.5 KiB
Python
import abc
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class AutoStorage:
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__counter = 0
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def __init__(self):
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cls = self.__class__
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prefix = cls.__name__
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index = cls.__counter
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self.storage_name = '_{}#{}'.format(prefix, index)
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cls.__counter += 1
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def __get__(self, instance, owner):
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if instance is None:
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return self
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else:
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return getattr(instance, self.storage_name)
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def __set__(self, instance, value):
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setattr(instance, self.storage_name, value)
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class Validated(abc.ABC, AutoStorage):
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def __set__(self, instance, value):
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value = self.validate(instance, value)
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super().__set__(instance, value)
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@abc.abstractmethod
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def validate(self, instance, value):
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"""return validated value or raise ValueError"""
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class Quantity(Validated):
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"""a number greater than zero"""
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def validate(self, instance, value):
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if value <= 0:
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raise ValueError('value must be > 0')
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return value
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class NonBlank(Validated):
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"""a string with at least one non-space character"""
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def validate(self, instance, value):
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value = value.strip()
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if len(value) == 0:
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raise ValueError('value cannot be empty or blank')
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return value
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# tag::MODEL_V6[]
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def entity(cls): # <1>
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for key, attr in cls.__dict__.items(): # <2>
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if isinstance(attr, Validated): # <3>
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type_name = type(attr).__name__
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attr.storage_name = '_{}#{}'.format(type_name, key) # <4>
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return cls # <5>
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# end::MODEL_V6[]
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