There is no if … on my screen nor there is one here https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon–20170313/033888.html. May be a typo?
In that case it cannot be a trailing closure because trailing closures are banned in such scenarios. https://github.com/apple/swift-evolution/blob/master/proposals/0056-trailing-closures-in-guard.md As for the lazy variables you’ve mentioned in the original posts, the closure there is invoked lately but only once and it cannot be reused at all. Let me know if I understood your gist now. if someFunction { …; return } // someFunction cannot have a trailing closure here! -- Adrian Zubarev Sent with Airmail Am 15. März 2017 um 12:08:19, Rien (r...@balancingrock.nl) schrieb: If I wrote this: if serverCert.write(to: certificateUrl) { showErrorInKeyWindow(message); return } then the meaning of return would have been different. Imo it is a problem that two pieces of code impact the understanding of each other and that those two pieces of code could potentially be very far apart. I do agree that the parenthesis are not a perfect solution, it was just the first thing that I could think of and that has some level of similarity in meaning. Regards, Rien Site: http://balancingrock.nl Blog: http://swiftrien.blogspot.com Github: http://github.com/Balancingrock Project: http://swiftfire.nl > On 15 Mar 2017, at 12:00, Adrian Zubarev <adrian.zuba...@devandartist.com> > wrote: > > I’m slightly confused by this. How is a trailing closure different from a > code block in Swift? It’s basically the same thing with some extra syntax > sugar because it happens to be the last parameter of your function. > > You can simply write this if you wanted to: > > myFucntion(someLabel: abc, closureLabel: { …; return }) > > Parentheses are indicating that your closure is immediately invoked. > > let someInt = { return 42 }() > print(someInt) > > let someClosureWhichReturnsAnInt = { return 42 } // You can reuse the closure > > print(someClosureWhichReturnsAnInt()) // Invocation happens now here > > return is scope based and it’s totally clear (to me) that in your case return > will return from your closure with a value of Void. > > > > > -- > Adrian Zubarev > Sent with Airmail > > Am 15. März 2017 um 11:35:39, Rien via swift-evolution > (swift-evolution@swift.org) schrieb: > >> 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 >> >> >> >> >> >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org >> https://lists.swift.org/mailman/listinfo/swift-evolution
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