[swift-evolution] Code blocks and trailing closures

[Kenny Leung]

I have proposed that a different keyword be used to return out of blocks. In Objective-C, I have a #define that aliases “blockreturn” and I use that exclusively in breaking out of blocks.

-Kenny


> On Mar 15, 2017, at 3:35 AM, Rien via swift-evolution <swift-evolution at swift.org> wrote:
> 
> What does the following code fragment do?
> 
> serverCert.write(to: certificateUrl) { showErrorInKeyWindow(message); return }
> 
> The only possible answer is: I don’t know.
> 
> The problem is finding out what the “return” statement will do.
> 
> Without knowing if the {...} is a code block or a trailing closure it is impossible to know what the return statement will do. It will either end the closure or it will end the function that contains this code block.
> 
> This could be disambiguated by using the same syntax as for lazy variables:
> 
> serverCert.write(to: serverCertificateUrl) { showErrorInKeyWindow(message: message); return }()
> 
> Now it is clear that the return statement will only terminate the (trailing) closure.
> 
> A question to the educators on the list: Is this a real problem?
> 
> Personally, I dislike this situation, but I am also ambivalent towards the solution I just described.
> 
> Regards,
> Rien
> 
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Balancingrock
> Project: http://swiftfire.nl
> 
> 
> 
> 
> 
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