2009/12/31 Martin McClure <martin@hand2mouse.com>:
If you run this in 1.1:
| dict | dict := WeakKeyDictionary new. dict at: 'foo' copy put: 'bar'. Smalltalk garbageCollect. dict associationsDo: [:assoc | self halt]. dict do: [:val | self halt]
It stops in the second halt, but not the first.
This is because #associationsDo: does not include associations whose keys have been GCed, but #do: *does* include values whose corresponding keys have been GCed.
This behavior seems inconsistent, and not particularly useful, and also seems to contradict the comments by the author in the Squeak bug from 2007, from which I'd think that #do: would not include the value which it currently does.
It is useful in terms, that sometimes you don't want to see the objects which GCed, but sometimes do. See how WeakRegistry using this. The lack of ephemerons support in VM, forcing us to deal with such things manually.
So I *think* this is an oversight, and is easy to fix by defining WeakKeyDictionary>>do: in terms of self associationsDo:.
But then there's the question of #size. The collection above answers 1 to #size, which also seems wrong.
#size for weak key dict is non-deterministic. Because even if you want to know the exact number of elements, you will need to iterate over the collection, but then, iteration can trigger GC, and you have a big chances to answer wrong value.
Comments?
Regards,
-Martin
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