<div dir="ltr">How about using a colon to separate it, to make `completion` look like an argument and to separate it from being a function? Something like this:<div><br></div><div><div><span class="Apple-tab-span" style="white-space:pre"> </span>UIView.animate(withDuration: 0.4) {</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>// animations</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>completion: { finished in</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>// completion</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>}</div></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr">On Thu, Jun 9, 2016 at 1:06 AM Brent Royal-Gordon via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">> Here's a common thing to say:<br>
><br>
> UIView.animate(withDuration:0.4, animations: {<br>
> self.v.backgroundColor = UIColor.red()<br>
> })<br>
><br>
> That's ugly. I'd rather write:<br>
><br>
> UIView.animate(withDuration:0.4) {<br>
> self.v.backgroundColor = UIColor.red()<br>
> }<br>
><br>
> What stops me is that `animations:` is not eligible for trailing closure syntax, because it isn't the last parameter — `completion:` is. But `completion:` has a default value, namely `nil` — that's why I'm allowed to omit it. So why can't the compiler work its way backwards through the parameters, and say to itself: "Well, I see a trailing closure, and I don't see any `animations:` label or any `completion:` label, so this trailing closure must be the `animations:` argument and the `completions:` argument must be `nil`."<br>
<br>
If we may take leave of practical considerations for a moment, I'd like to note that the ideal syntax for a call like this would probably look like:<br>
<br>
UIView.animate(withDuration: 0.4) {<br>
// animations<br>
}<br>
completion { finished in<br>
// completion<br>
}<br>
<br>
And of course, since `completion` has a default value, this would naturally degrade to:<br>
<br>
UIView.animate(withDuration: 0.4) {<br>
// animations<br>
}<br>
<br>
I'm guessing this isn't possible because the `completion` could instead be a call to a separate function with a trailing closure. But is there some way we could get something similar? That could significantly improve our handling of multi-block APIs and give trailing closures the ability to emulate more kinds of syntax.<br>
<br>
--<br>
Brent Royal-Gordon<br>
Architechies<br>
<br>
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</blockquote></div><div dir="ltr">-- <br></div><div data-smartmail="gmail_signature"><div dir="ltr">-Saagar Jha</div></div>