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50633e7353
The SubfieldBase's descriptor caused an AttributeError when accessed from the class. Introspection didn't like that. Patch by Trac alias supervacuo.
57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
"""
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Convenience routines for creating non-trivial Field subclasses, as well as
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backwards compatibility utilities.
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Add SubfieldBase as the metaclass for your Field subclass, implement
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to_python() and the other necessary methods and everything will work
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seamlessly.
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"""
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class SubfieldBase(type):
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"""
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A metaclass for custom Field subclasses. This ensures the model's attribute
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has the descriptor protocol attached to it.
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"""
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def __new__(cls, name, bases, attrs):
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new_class = super(SubfieldBase, cls).__new__(cls, name, bases, attrs)
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new_class.contribute_to_class = make_contrib(
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new_class, attrs.get('contribute_to_class')
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)
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return new_class
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class Creator(object):
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"""
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A placeholder class that provides a way to set the attribute on the model.
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"""
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def __init__(self, field):
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self.field = field
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def __get__(self, obj, type=None):
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if obj is None:
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return self
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return obj.__dict__[self.field.name]
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def __set__(self, obj, value):
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obj.__dict__[self.field.name] = self.field.to_python(value)
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def make_contrib(superclass, func=None):
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"""
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Returns a suitable contribute_to_class() method for the Field subclass.
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If 'func' is passed in, it is the existing contribute_to_class() method on
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the subclass and it is called before anything else. It is assumed in this
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case that the existing contribute_to_class() calls all the necessary
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superclass methods.
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"""
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def contribute_to_class(self, cls, name):
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if func:
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func(self, cls, name)
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else:
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super(superclass, self).contribute_to_class(cls, name)
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setattr(cls, self.name, Creator(self))
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return contribute_to_class
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