<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 9 Jul 2016, at 06:34, Zhao Xin <<a href="mailto:owenzx@gmail.com" class="">owenzx@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="gmail_default" style="font-family:georgia,serif">The compiler is not smart enough to treat this as you think, nor it will be designed to. According to the documents, it is the developer‘s burden to add @noescape or weak or unowned. So I disagree it is a bug.</div><div class="gmail_default" style="font-family:georgia,serif"><br class=""></div><div class="gmail_default" style="font-family:georgia,serif">Zhaoxin</div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Sat, Jul 9, 2016 at 7:30 AM, Karl <span dir="ltr" class=""><<a href="mailto:razielim@gmail.com" target="_blank" class="">razielim@gmail.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><span class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 5 Jul 2016, at 03:47, Zhao Xin <<a href="mailto:owenzx@gmail.com" target="_blank" class="">owenzx@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class=""><div class="gmail_default" style="font-family:georgia,serif">No, it is not a bug.</div><div class="gmail_default" style="font-family:georgia,serif"><br class=""></div><div class="gmail_default" style="font-family:georgia,serif">For a closure, you have to call self explicitly unless the closure is mark as @noescape. Also, in this situation, self is not unowned, as the closure is not stored, it ran and released. Below, is a situation that you need use unowned self. Here the closure is stored in variable d instead of running and releasing.</div><div class="gmail_default" style="font-family:georgia,serif"><br class=""></div><div class="gmail_default"><div class="gmail_default"><font face="georgia, serif" class=""> lazy var d:()->Int = { [unowned self] in</font></div><div class="gmail_default"><font face="georgia, serif" class=""> return self.a*self.b</font></div><div class="gmail_default"><font face="georgia, serif" class=""> }</font></div><div class="gmail_default"><font face="georgia, serif" class=""><br class=""></font></div><div class="gmail_default"><font face="georgia, serif" class="">Zhaoxin</font></div></div></div></div></blockquote></div><br class=""></span><div class="">In this specific case, when you are initialising from a closure, there is no need to make the capture of ‘self’ explicit and it’s totally safe for it to be unowned. You can’t invoke the closure without going through a valid instance, and that instance always owns the closure and never the other way around.</div></div></blockquote></div><br class=""></div>
</div></blockquote></div><br class=""><div class=""><br class=""></div><div class="">I know that the compiler doesn’t do this today, but I disagree that it will never have enough information to make inferences like this. It would simply be an adaptation of ARC to Swift - you don’t have these kind of attached lazy closures in Obj-C, so there was never any need for it. They run in the context of the instance just like a getter would, so they should have the same properties as a getter (including implicit ‘self’).</div><div class=""><br class=""></div><div class="">In general though, I think we are moving to “property behaviours”, which may need something like this in general. You would want to use unowned references in a stored property behaviour object; any retains/releases would be unnecessary. I’m sure we’ll talk about it more when that gets further along.</div><div class=""><br class=""></div><div class="">Karl</div></body></html>