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