[swift-evolution] [Proposal] Scoped resources (like C# using statement)

Matthew Johnson matthew at anandabits.com
Wed Dec 30 17:23:08 CST 2015

> On Dec 30, 2015, at 5:19 PM, Kevin Ballard via swift-evolution <swift-evolution at swift.org> wrote:
> On Wed, Dec 30, 2015, at 03:12 PM, Kevin Wooten via swift-evolution wrote:
>>>> Another possibility I've thought of is defining `defer { val }` to guarantee that val remains alive until the defer fires on scope exit. That might let us leave `defer` as the one "guarantee something happens exactly at scope exit" language construct.
>> What about this…
>> defer let val = grabOrCreateSomething() {
>>   return;
>> }
>> Seems natural once you learn guard.
> Natural? I have no idea what you're expecting that expression to actually do. What is a "defer let”?

I think the idea is that a local variable declared with a `defer` modifier has its lifetime extended until the scope exits.  It is a slightly more compact version of what Joe suggested.  But I agree that it has potential for confusion - it reads like it is deferring the initialization of `val` until the scope exits which would be rather pointless.

I do like the idea of making the extended lifetime part of the local variable declaration but I’m not sure about how this specific syntax reads.

> -Kevin
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151230/fddb5e37/attachment.html>

More information about the swift-evolution mailing list