[swift-evolution] Guaranteed closure execution

[Gwendal Roué]

Hello all,

I was wondering if this topic had evolved in anyway since its original introduction.

@noescape(once) would still be a useful addition to the language!

Gwendal Roué



> Le 3 févr. 2016 à 22:21, Félix Cloutier via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> I updated the proposal to address some concerns. It can be found at: https://github.com/zneak/swift-evolution/blob/master/proposals/00xx-noescape-once.md <https://github.com/zneak/swift-evolution/blob/master/proposals/00xx-noescape-once.md>
> 
> Things that changed:
> 
> It now says that the closure must be called on code paths where the function throws;
> you can have multiple @noescape(once) parameters but they can't make assumptions from one another.
> 
> I'm not 100% convinced that forcing a call on code paths that throw is always desirable. I've changed it because Chris's support probably means that the feature has better chances of making it, but I'm not convinced yet. If throwing allows me to return without calling the closure, I can write this:
> 
> do {
> 	let foo: Int
> 	try withLock(someLock, timeout: 0.5) {
> 		foo = sharedThing.foo
> 	}
> } catch {
> 	print("couldn't acquire lock fast enough")
> }
> 
> which would be kind of messy if instead, the closure needed a parameter to tell whether the lock was acquired or not when it runs.
> 
> Félix
> 
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