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from __future__ import absolute_import
class StateObject(object):
def _get_state(self):
raise NotImplementedError # pragma: nocover
def _load_state(self, state):
raise NotImplementedError # pragma: nocover
@classmethod
def _from_state(cls, state):
raise NotImplementedError # pragma: nocover
# Usually, this function roughly equals to the following code:
# f = cls()
# f._load_state(state)
# return f
def __eq__(self, other):
try:
return self._get_state() == other._get_state()
except AttributeError: # we may compare with something that's not a StateObject
return False
def __ne__(self, other):
return not self.__eq__(other)
class SimpleStateObject(StateObject):
"""
A StateObject with opionated conventions that tries to keep everything DRY.
Simply put, you agree on a list of attributes and their type.
Attributes can either be primitive types(str, tuple, bool, ...) or StateObject instances themselves.
SimpleStateObject uses this information for the default _get_state(), _from_state(s) and _load_state(s) methods.
Overriding _get_state or _load_state to add custom adjustments is always possible.
"""
_stateobject_attributes = None # none by default to raise an exception if definition was forgotten
"""
An attribute-name -> class-or-type dict containing all attributes that should be serialized
If the attribute is a class, this class must be a subclass of StateObject.
"""
def _get_state(self):
return {attr: self._get_state_attr(attr, cls)
for attr, cls in self._stateobject_attributes.iteritems()}
def _get_state_attr(self, attr, cls):
"""
helper for _get_state.
returns the value of the given attribute
"""
val = getattr(self, attr)
if hasattr(val, "_get_state"):
return val._get_state()
else:
return val
def _load_state(self, state):
for attr, cls in self._stateobject_attributes.iteritems():
self._load_state_attr(attr, cls, state)
def _load_state_attr(self, attr, cls, state):
"""
helper for _load_state.
loads the given attribute from the state.
"""
if state.get(attr, None) is None:
setattr(self, attr, None)
return
curr = getattr(self, attr)
if hasattr(curr, "_load_state"):
curr._load_state(state[attr])
elif hasattr(cls, "_from_state"):
setattr(self, attr, cls._from_state(state[attr]))
else:
setattr(self, attr, cls(state[attr]))
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