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.send { color:#77bb77; }
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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>There is no <code>if …</code> on my screen nor there is one here <a href="https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170313/033888.html">https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon–20170313/033888.html</a>. May be a typo?</p>
<p>In that case it cannot be a trailing closure because trailing closures are banned in such scenarios. <a href="https://github.com/apple/swift-evolution/blob/master/proposals/0056-trailing-closures-in-guard.md">https://github.com/apple/swift-evolution/blob/master/proposals/0056-trailing-closures-in-guard.md</a></p>
<p>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.</p>
<p>Let me know if I understood your gist now.</p>
<pre><code class="swift">if someFunction { …; return } // someFunction cannot have a trailing closure here!
</code></pre>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1489576288160509952" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 15. März 2017 um 12:08:19, Rien (<a href="mailto:rien@balancingrock.nl">rien@balancingrock.nl</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>If I wrote this:
<br>
<br>if serverCert.write(to: certificateUrl) { showErrorInKeyWindow(message); return }
<br>
<br>then the meaning of return would have been different.
<br>
<br>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.
<br>
<br>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.
<br>
<br>Regards,
<br>Rien
<br>
<br>Site: http://balancingrock.nl
<br>Blog: http://swiftrien.blogspot.com
<br>Github: http://github.com/Balancingrock
<br>Project: http://swiftfire.nl
<br>
<br>
<br>
<br>
<br>
<br>> On 15 Mar 2017, at 12:00, Adrian Zubarev <adrian.zubarev@devandartist.com> wrote:
<br>>
<br>> 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.
<br>>
<br>> You can simply write this if you wanted to:
<br>>
<br>> myFucntion(someLabel: abc, closureLabel: { …; return })
<br>>
<br>> Parentheses are indicating that your closure is immediately invoked.
<br>>
<br>> let someInt = { return 42 }()
<br>> print(someInt)
<br>>
<br>> let someClosureWhichReturnsAnInt = { return 42 } // You can reuse the closure
<br>> print(someClosureWhichReturnsAnInt()) // Invocation happens now here
<br>>
<br>> 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.
<br>>
<br>>
<br>>
<br>>
<br>> --
<br>> Adrian Zubarev
<br>> Sent with Airmail
<br>>
<br>> Am 15. März 2017 um 11:35:39, Rien via swift-evolution (swift-evolution@swift.org) schrieb:
<br>>
<br>>> What does the following code fragment do?
<br>>>
<br>>> serverCert.write(to: certificateUrl) { showErrorInKeyWindow(message); return }
<br>>>
<br>>> The only possible answer is: I don’t know.
<br>>>
<br>>> The problem is finding out what the “return” statement will do.
<br>>>
<br>>> 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.
<br>>>
<br>>> This could be disambiguated by using the same syntax as for lazy variables:
<br>>>
<br>>> serverCert.write(to: serverCertificateUrl) { showErrorInKeyWindow(message: message); return }()
<br>>>
<br>>> Now it is clear that the return statement will only terminate the (trailing) closure.
<br>>>
<br>>> A question to the educators on the list: Is this a real problem?
<br>>>
<br>>> Personally, I dislike this situation, but I am also ambivalent towards the solution I just described.
<br>>>
<br>>> Regards,
<br>>> Rien
<br>>>
<br>>> Site: http://balancingrock.nl
<br>>> Blog: http://swiftrien.blogspot.com
<br>>> Github: http://github.com/Balancingrock
<br>>> Project: http://swiftfire.nl
<br>>>
<br>>>
<br>>>
<br>>>
<br>>>
<br>>> _______________________________________________
<br>>> swift-evolution mailing list
<br>>> swift-evolution@swift.org
<br>>> https://lists.swift.org/mailman/listinfo/swift-evolution
<br>
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