[swift-users] for with optional collection?

[Jacob Bandes-Storch]

To me it would seem more logical as "for x in array? { }" — to parallel
"for case let x? in array { }"


On Fri, Feb 10, 2017 at 1:03 PM, Rick Mann via swift-users <
swift-users at swift.org> wrote:

> I love the idea of for in? (Or even for? In). You should pitch that to
> evolution.
>
> Sent from my iPhone
>
> On Feb 10, 2017, at 07:04, Tino Heth <2th at gmx.de> wrote:
>
>
> Is there any concise way to write the following?
>
> if let collection = someOptionalCollection
> {
>    for item in collection
>    {
>    }
> }
>
> I've been thinking about that lately, but haven't had the time to look
> wether someone on evolution already proposed a "for in?"-loop…
>
> Imho the "forEach" solution is flawed, because you can't break the loop,
> and the "?? []" isn't perfect either:
> I hope the compiler can optimise so that the assembly is as fast as the
> "if let" solution, but even if this is the case, it is not obvious for a
> human reader.
>
> This
>
> extension Optional where Wrapped: Sequence {
> var elements: [Wrapped.Iterator.Element] {
> switch (self) {
> case .none:
> return []
> case .some(let o):
> return Array(o)
> }
> }
> }
>
> let test: [Int]? = nil
> for i in test.elements {
> print(i)
> }
>
> looks nice to me (except the return type — I guess there are better
> options), but I don't expect that the compiler can do much to optimise it.
>
> for i in? test {
> print(i)
> }
>
> Imho looks even better, but this would need an extension of the language
> itself…
>
>
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170210/12eb33e1/attachment.html>