Greg Brown <[email protected]> wrote:
This approach allows us to combine collection behaviors without
collisions on the Iterable type (for example,
org.apache.pivot.xml.Element implements List<Node> and
Dictionary<String, String>, which wouldn't compile if Dictionary
also implemented Iterable).
I didn't suggest that Dictionary<K,V> should implement Iterable.
I would not be feasible anyway: should it iterate on the keys or the values?
Map<K, V> iterates over keys (since it extends Collection<K>).
Pivot's collections all follow the same pattern:
List<T> : Sequence<T>, Collection<T>
Map<K, V> : Dictionary<K, V>, Collection<K>
Set<E> : Group<E>, Collection<E>
I see. I still fail to see the collision, but I see now that you have
a different understanding, or rather a different "vision", of how a
collection library should look like. See, my understanding is that
(almost) everything is a sequence, with maps being sequences of pairs,
and a collection is an enhanced sequence which can be updated. So IMHO
it would look like this:
List<T> extends Sequence<T> extends Iterable<T>, Collection<T>
Map<K, V> extends Dictionary<K, V> extends Sequence<Pair<K,V>>,
Collection<K>
Set<E> extends Group<E> extends Iterable<E>, Collection<E>
But I'm not a library designer, so I should probably keep my mouth
shut. I'll stop babbling about it and won't raise this issue again.
Thanks, Greg, for your detailed explanations!
It wouldn't make sense to make Sequence iterable
You're the first person I get to know who says that sequences are not
iterable. ;-)
Iterating over a list using indices is sooo 90ies. Why can't I simply write:
for (Object row : tableView.getSelectedRows()) {
...
}
That's true, but getSelectedRows() is primarily meant to be a
convenience method. The primary means of obtaining a table view's
selection is getSelectedRanges(). This method returns an instance of
ListSelectionSequence, which could (and probably should) implement
Iterable.
That's ok, it would help in this case. Note that you need to make
getSelectedRanges() return ListSelectionSequence instead of
Sequence<Span>. And ListSelectionSequence needs to be public. (And,
btw., you are making just one more class, which is implementing
Sequence directly (but not List), implement Iterable. ;-)
Please don't forget ListView.getSelectedRanges(), too.
Uh, and TreeView.getSelectedPaths(). And
FileBrowser(Sheet).getSelectedFiles().
You might suggest that getSelectedRows() return a List. We don't do
this because it might imply that the return value is a "live"
collection to which the caller can listen for updates, which is not
the case.
So you're saying that any list that is not "live" is a sequence and is
not iterable?!? That's odd. (Sorry, can't stop :-)
Regards,
Dirk.
