[swift-evolution] Guaranteed closure execution

[Gwendal Roué]

> Le 1 févr. 2016 à 18:29, Félix Cloutier via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> @Gwendal: that's one solution. A third solution would be to enforce that @noescape(once) parameters are executed in parameter order.
> 
> Do you have any example of UIKit where a function accepts two closures that could reasonably be marked @noescape(once)?

No Félix, no example in UIKit itself. I was thinking of higher-order applications or library functions that wrap any stateful API. A very artificial example involving UIKit :

	func f(@noescape(once) closure1: () -> (), @noescape(once) closure2: () -> (), @noescape(once) closure3: () -> ()) {
		closure1()
		tableView.beginUpdates()
		closure2()
		tableView.endUpdates()
		closure3()
	}

So unless it would be too complex to implement, I would support letting the compiler accept several once closures, without requiring any execution order, and without double-guessing the needs of the developer.

Gwendal
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