Extrinsic reference registries
Project description
Extrinsic Key References
See src/zc/extrinsicreference/README.txt for details.
Detailed Documentation
Extrinsic References
Extrinsic reference registries record a key and one or more values to which they refer. The key and all values must be adaptable to zope.app.keyreference.interfaces.IKeyReference.
>>> import zc.extrinsicreference >>> references = zc.extrinsicreference.ExtrinsicReferences() >>> references.add(1, 2) Traceback (most recent call last): ... TypeError: ('Could not adapt', 1... >>> from zope import interface, component >>> from zope.app.keyreference.interfaces import IKeyReference >>> class IMyObject(interface.Interface): ... "An interface for which we register an IKeyReference adapter" ... id = interface.Attribute("An id unique to IMyObject instances") ... >>> class MyObject(object): ... interface.implements(IMyObject) ... _id_counter = 0 ... @classmethod ... def _getId(cls): ... val = cls._id_counter ... cls._id_counter += 1 ... return val ... def __init__(self): ... self.id = self._getId() ... >>> class DummyKeyReference(object): ... interface.implements(IKeyReference) ... component.adapts(IMyObject) ... key_type_id = 'zc.extrinsicreference.doctest' ... def __init__(self, obj): ... self.object = obj ... def __call__(self): ... """Get the object this reference is linking to. ... """ ... return self.object ... def __hash__(self): ... """Get a unique identifier of the referenced object. ... """ ... return hash(self.object.id) ... def __cmp__(self, other): ... """Compare the reference to another reference. ... """ ... if self.key_type_id == other.key_type_id: ... return cmp(self.object.id, other.object.id) ... return cmp(self.key_type_id, other.key_type_id) ... >>> component.provideAdapter(DummyKeyReference) >>> object1 = MyObject() >>> references.add(object1, 2) Traceback (most recent call last): ... TypeError: ('Could not adapt', 2... >>> value1 = MyObject() >>> value2 = MyObject() >>> references.add(object1, value1) >>> references.add(object1, value2)
Values can be retrieved by their key:
>>> set(references.get(object1)) == set((value1, value2)) True
References can be removed:
>>> references.remove(object1, value1) >>> list(references.get(object1)) == [value2] True
But if the reference is not registered, removing it raises a KeyError.
>>> references.remove(object1, value1) Traceback (most recent call last): ... KeyError:... >>> object2 = MyObject() >>> references.remove(object2, value2) Traceback (most recent call last): ... KeyError:...
If you prefer to silently ignore these errors, use discard.
>>> references.discard(object1, value1) >>> references.discard(object2, value2)
Otherwise, you can use contains to determine if the reference exists:
>>> references.contains(object1, value1) False >>> references.contains(object2, value2) False >>> references.contains(object1, value2) True
If a key has no associated values, an empty iterable is returned:
>>> references.discard(object1, value2) >>> list(references.get(object1)) []
Adding a value more than once does not cause the value to be included in the result sequence more than once:
>>> references.add(object1, value1) >>> references.add(object1, value1) >>> list(references.get(object1)) == [value1] True
The set method destructively sets the given values for the object. Repeated objects are collapsed to a single instance.
>>> references.set(object1, (value2, object2, value2, value2, object2)) >>> references.contains(object1, value1) False >>> len(list(references.get(object1))) 2 >>> set(references.get(object1)) == set((value2, object2)) True >>> references.set(object1, ()) >>> len(list(references.get(object1))) 0
The update method adds values to the previous values, non-destructively.
>>> references.add(object1, value1) >>> references.update(object1, (value2, object2, value2)) >>> len(list(references.get(object1))) 3 >>> set(references.get(object1)) == set((value1, value2, object2)) True
CHANGES
0.3.0 (2009-08-27)
Fix errors introduced in 0.2.0 refactoring:
Stop referring to extrinsicreference module from ZCML. The code is now in __init__.py.
Revert registerShortcut and unregisterShortcut changes. These two functions are handlers in track_shortcuts.zcml.
Add more package infrastructure, such as this file.
0.2.0 (2009-08-26)
Refactored an existing stable code.
Initial release as an egg.
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