[swift-evolution] The bind thread
Erica Sadun
erica at ericasadun.com
Mon Feb 1 13:27:32 CST 2016
It would have to be something along the lines of $0 wouldn't it? If there was no clear single symbol to shadow?
That's a very good point, and thank you for bringing it up.
-- Erica
> On Feb 1, 2016, at 12:22 PM, T.J. Usiyan <griotspeak at gmail.com> wrote:
>
> This is interesting. What name is created by
>
> if bind foo.somethingReturningAnOptional {
> // ???
> }
>
> On Mon, Feb 1, 2016 at 2:18 PM, Erica Sadun via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> Joe says "If you all are serious about this, I think you should start a new thread about it."
> I think it's worth a serious discussion just so it can be evaluated and either adopted or discarded
> and dropped forever. Here goes.
>
> INTRO
>
> The if let x = x {...} and guard let x = x else {...} constructs do something with let (and var) that's
> fundamentally different from let (and var) elsewhere in the language. The same keywords are used to conditionally unwrap
> and bind an item, not just shadow that item's current value.
>
> Introducing a new bind keyword to indicate unwrapping and binding would disambiguate these uses.
>
> DETAIL DESIGN:
>
> Jacob Bandes-Storch offers two common use-cases. I prefer his "if bind foo" to my original "if bind foo = foo":
>
> if bind foo {
> // foo is non-optional in here
> }
>
> somethingAsync { [weak self] in
> guard bind self else { return }
> // ...
> }
>
> JBS's approach offers my original "bind" keyword to unwrap and shadow bind, but also provides a way to
> strongly bind a weak reference to self, which (presumably) would allow self semantics in the remaining
> lifetime of that scope.
>
> ALTERNATIVE PROPOSALS:
>
> Tino Heth proposes a second use-case one with different semantics. This case, it seems to make an
> alias rather than using binding for shadowing:
>
> bind x = a.property.with.a.long.path
> print x // 42
> print(a.property.with.a.long.path == 42) => true
>
> presumably this means:
>
> x += 1
> print(a.property.with.a.long.path) // 43
>
> DISCUSSION
>
> I'm throwing these both out there. I have nothing to really say about Tino's but I do think my and Jacob's
> proposal has the advantages of:
>
> * Simplifying an mildly complex and potentially misleading statement
> * Creating a deliberate and controlled rather than accidental shadowing style
>
> Have at it.
>
> -- Erica
>
>
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160201/656880af/attachment.html>
More information about the swift-evolution
mailing list