def with_properties(cls, **properties):
"""
Returns a clone of the class whose :attr:`properties` contain the given
`properties` in addition to the ones inherited from this one.
"""
return cls.using(
properties=InheritingDictDescriptor('properties', **properties))
class BaseElement(object):
"""
A base class for elements, that allows describing python objects or
meta-elements - elements that affect other elements but do not themselves
describe data.
.. versionadded:: 2.1.0
Was previously part of :class:`Element`, is now split up into a separate
class.
"""
#: A dictionary whose contents are inherited by subclasses, which should be
#: used for application-specific information associated with an element.
properties = InheritingDictDescriptor('properties')
name = Unnamed
@class_cloner
def using(cls, **kwargs):
"""
Returns a clone of the class whose attributes have been overwritten
with the given keyword arguments.
"""
for key, value in iteritems(kwargs):
if not hasattr(cls, key):
raise TypeError("unexpected keyword argument %r" % key)
setattr(cls, key, value)
return cls
@classmethod
def with_properties(cls, **properties):
"""
Returns a clone of the class whose :attr:`properties` contain the given
`properties` in addition to the ones inherited from this one.
"""
return cls.using(
properties=InheritingDictDescriptor('properties', **properties))
def __init__(self, value=Unspecified):
#: Defines the validation state of the element, may be one of the
#: following values:
#:
#: `None`
#: The element has not been validated, yet.
#:
#: `True`
#: The element is valid.
#:
#: `False`
#: The element is not valid.
self.is_valid = None
#: The unserialized concrete value this element represents. May also be
#: :data:`~relief.Unspecified` if the value has not been set or
#: :data:`~relief.NotUnserializable` if :meth:`unserialize` was unable
#: to unserialize the value.
self.value = Unspecified
#: The concrete value this element represents. May also be
#: :data:`~relief.Unspecified` if the value has not been set. This may
#: be helpful to look at if :attr:`value` is
#: :data:`~relief.NotUnserializable`.
self.raw_value = Unspecified
self.set_from_raw(value)
def set_from_native(self, value):
"""
Sets :attr:`value` to the given `value` and sets attr:`raw_value` to
the serialized form of `value`.
.. versionadded:: 1.0.0
"""
self.value = value
self.raw_value = self.serialize(value)
self.is_valid = None
def set_from_raw(self, raw_value):
"""
Sets :attr:`raw_value` with the given `raw_value` and sets
:attr:`value` to the unserialized form of `raw_value` if applicable.
.. versionadded:: 1.0.0
Was previously named :meth:`set`.
"""
self.raw_value = raw_value
self.value = self.unserialize(raw_value)
self.is_valid = None
def serialize(self, value):
"""
Tries to serialize the given `value` and returns an object than can be
unserialized with :meth:`unserialize`.
.. versionadded:: 1.0.0
"""
return value
def unserialize(self, raw_value):
"""
Tries to unserialize the given `raw_value` and returns an object whose
type matches the type described by the element.
return raw_value
"""
return raw_value
def __str__(self):
return str(self.value)
class Foo(object):
properties = InheritingDictDescriptor('properties', foo=1)