102 lines
3.2 KiB
Python
102 lines
3.2 KiB
Python
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class ValidationError(Exception):
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pass
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class BaseField(object):
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"""A base class for fields in a MongoDB document. Instances of this class
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may be added to subclasses of `Document` to define a document's schema.
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"""
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def __init__(self, name=None, default=None):
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self.name = name
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self.default = default
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def __get__(self, instance, owner):
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"""Descriptor for retrieving a value from a field in a document. Do
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any necessary conversion between Python and MongoDB types.
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"""
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if instance is None:
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# Document class being used rather than a document object
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return self
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# Get value from document instance if available, if not use default
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value = instance._data.get(self.name)
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if value is not None:
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value = self._to_python(value)
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elif self.default is not None:
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value = self.default
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if callable(value):
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value = value()
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return value
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def __set__(self, instance, value):
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"""Descriptor for assigning a value to a field in a document. Do any
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necessary conversion between Python and MongoDB types.
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"""
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if value is not None:
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try:
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value = self._to_python(value)
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self._validate(value)
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value = self._to_mongo(value)
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except ValueError:
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raise ValidationError('Invalid value for field of type "' +
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self.__class__.__name__ + '"')
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instance._data[self.name] = value
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def _to_python(self, value):
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"""Convert a MongoDB-compatible type to a Python type.
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"""
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return unicode(value)
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def _to_mongo(self, value):
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"""Convert a Python type to a MongoDB-compatible type.
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"""
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return self._to_python(value)
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def _validate(self, value):
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"""Perform validation on a value.
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"""
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return value
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class DocumentMetaclass(type):
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"""Metaclass for all documents.
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"""
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def __new__(cls, name, bases, attrs):
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doc_fields = {}
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# Include all fields present in superclasses
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for base in bases:
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if hasattr(base, '_fields'):
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doc_fields.update(base._fields)
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# Add the document's fields to the _fields attribute
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for attr_name, attr_val in attrs.items():
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if issubclass(attr_val.__class__, BaseField):
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if not attr_val.name:
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attr_val.name = attr_name
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doc_fields[attr_name] = attr_val
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attrs['_fields'] = doc_fields
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return type.__new__(cls, name, bases, attrs)
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class BaseDocument(object):
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def __init__(self, **values):
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self._data = {}
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# Assign initial values to instance
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for attr_name, attr_value in self._fields.items():
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if attr_name in values:
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setattr(self, attr_name, values.pop(attr_name))
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else:
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# Use default value
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setattr(self, attr_name, getattr(self, attr_name))
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def __iter__(self):
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# Use _data rather than _fields as iterator only looks at names so
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# values don't need to be converted to Python types
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return iter(self._data)
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