[swift-evolution] #selector and Void methods

[Joe Groff]

> On Mar 22, 2016, at 8:49 PM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org> wrote:
> 
> So, today is day 2 of Swift 2.2 being in the hands of mere mortals. This evening, I walked into my weekly NSCoder Night meeting and talked to a pretty experienced developer struggling with this:
> 
> 	class EditEventViewController: UIViewController {
> 		...
> 		@IBAction func cancel(sender: AnyObject?) {
> 			cancel()
> 		}
> 		func cancel() {
> 			// actual canceling logic is here
> 		}
> 	}
> 	
> 	class EditEventContainerViewController: UIViewController {
> 		...
> 		func prepareForSegue(_ segue: UIStoryboardSegue, sender sender: AnyObject?) {
> 			switch segue.identifier {
> 				...
> 				let cancelButton = UIBarButtonItem(barButtonSystemItem: .Cancel, target: nil, action: nil)
> 				cancelButton.target = vc
> 				cancelButton.action = #selector(vc.cancel)	// This is the problem line
> 				...
> 			}
> 		}
> 	}
> 		
> `vc.cancel` was, of course, ambiguous, and the SE-0021 `vc.cancel(_:)` syntax can't select a Void function. I had to explain how to use `as Void -> Void` to select the right version.
> 
> This is merely an anecdote, but I think it may end up being an issue.

Thanks for reporting this. I also saw this come up at least one other place:

https://twitter.com/bendodson/status/712208662933200896

I wonder if it's worth making #selector(vc.cancel()) work. What do you think, Doug?

-Joe