59 lines
1.8 KiB
Python
59 lines
1.8 KiB
Python
import weakref
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__all__ = ['WeakMethod']
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__version__ = '1.0.0'
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class WeakMethod(weakref.ref):
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"""
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A custom 'weakref.ref' subclass which simulates a weak reference to
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a bound method, working around the lifetime problem of bound methods
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"""
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__slots__ = '_func_ref', '_meth_type', '_alive', '__weakref__'
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def __new__(cls, meth, callback=None):
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try:
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obj = meth.__self__
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func = meth.__func__
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except AttributeError:
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raise TypeError('argument should be a bound method, not {}'.format(type(meth)))
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def _cb(arg):
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# The self-weakref trick is needed to avoid creating a reference cycle.
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self = self_wr()
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if self._alive:
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self._alive = False
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if callback is not None:
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callback(self)
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self = weakref.ref.__new__(cls, obj, _cb)
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self._func_ref = weakref.ref(func, _cb)
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self._meth_type = type(meth)
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self._alive = True
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self_wr = weakref.ref(self)
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return self
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def __call__(self):
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obj = super(WeakMethod, self).__call__()
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func = self._func_ref()
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if obj is None or func is None:
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return None
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return self._meth_type(func, obj)
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def __eq__(self, other):
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if isinstance(other, WeakMethod):
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if not self._alive or not other._alive:
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return self is other
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return weakref.ref.__eq__(self, other) and self._func_ref == other._func_ref
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return False
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def __ne__(self, other):
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if isinstance(other, WeakMethod):
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if not self._alive or not other._alive:
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return self is not other
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return weakref.ref.__ne__(self, other) or self._func_ref != other._func_ref
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return True
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__hash__ = weakref.ref.__hash__
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