You say "and you're searching for them in JS (as I was)". Had the abstraction been called ObjectMap or ObjectRegistry, would you have found it?
I don't think the API name is the only way someone can discover what they're looking for. Proper documentation for "ObjectMap" which said "keyrefs are held weakly" or something to that respect would probably have ended up on my search radar.
Of course, if the WeakMap really was both weak-key and weak-value, then I'd absolutely expect the name to be WeakMap (I think "weak" in this case is a useful and non-trivial part of the behavior). So my complaint is not "Weak", but that "Weak" implies something more comprehensive than is actually the case. It over-promises and under-delivers, so to speak.
I should also clarify my process for how I found this API (I over-simplified in my previous email). I actually started out with both the weakref need AND the object-as-key ("map") need. For the object-as-key need, I had already constructed a dual-numerically-indexed-array solution to associating an object with a value. But then, realizing that this was not only clunky, but also was going to make manual GC (that is, cleaning up the entries if the object is removed) also more awkward/less performant, I started looking for an API that would do both: Map (object-as-key) and automatically clean up the entries in the Map if either the key-object or the value-object (in my case, both DOM objects) were GC'd.
In that context (and in support of Allen's early assertions), "Map" in the name was most important to focus me into a (theoretical) class of APIs (if there were indeed several different kinds of maps). Then I would have searched through the documentation to see if any of the Maps had the "weak" behavior I was looking for.
OTOH, had I *only* been looking for pure Weak References, and not a Map structure, then I'd have been looking for some API like "WeakRef", and actually "Map" probably would have been confusing or ignorable noise.
As it was, you found the right thing to look at and think about, but you needed to read more before you understood whether it serves your actual purpose.
I found it because a fellow Mozilla dev said "hey, that sounds like WeakMaps" and I thought "awesome, ask and ye shall find". Of course, the devil was in the details, because it wasn't actually what I needed completely. This was compounded by the fact that the MDN documentation (at least at the time) was ambiguous and didn't make it clear that only keys were "weak". So a well-experienced co-worker and the documentation BOTH were confused (as were several others through various IRC chats) as to exactly what was and was not "weak" in the WeakMap.
How did I figure it out? By writing it into my code, and then seeing mem-leak tests fail. Thankfully, I eventually found some IRC people who clarified that what I was seeing was not a bug but was in fact by-design. But, that's a hard way to learn the lesson.
Would a more accurate name have helped? Perhaps. "WeakKeyMap" certainly would have made it obvious that the Map was not fully "weak". Would more accurate documentation have helped? Absolutely. Would naming *and* documentation have helped other co-workers not be misled and consequently point me in the wrong path? I hope so.
That's why I like "WeakMap" best -- it is the mapping that is weak, not the keys or the values.
I understand what you're saying here. But as I mentioned before, the way my (far less informed) brain thinks about it, the "map" or "link" between two objects should in fact be weak and ephemeral enough that either side going away (being GC'd) should be enough to cause the link between the two to be cleaned up. I think it's because I tend to think of "Map" as more 2-way than one-way, though I understand it's technically only 1-way.
Saying it a different way... if the focus is on the map or link itself, and the RHS thing the map/link is pointing to is no longer valid/defined, then what use is there keeping a link that points to something now undefined?
It just seems a little unfortunate/misleading to me that from an implementation perspective, creating the map/link is sufficient to prevent the RHS value in question from ever getting to that "undefined" state. When I create a reference using variables/properties, I *expect* a hard reference that behaves like that. But when I use a specialized API with "Weak" in the name, I definitely expect the opposite.
--Kyle _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
