<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=""><blockquote type="cite" class="">On Aug 26, 2016, at 2:58 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" class="">xiaodi.wu@gmail.com</a>> wrote:<br class=""></blockquote><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">On Fri, Aug 26, 2016 at 2:48 PM, Charles Srstka<span class="Apple-converted-space"> </span></span><span dir="ltr" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><<a href="mailto:cocoadev@charlessoft.com" target="_blank" class="">cocoadev@charlessoft.com</a>></span><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class=""><span class="Apple-converted-space"> </span></span><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">wrote:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div style="word-wrap: break-word;" class=""><span class=""><blockquote type="cite" class="">On Aug 26, 2016, at 2:38 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank" class="">xiaodi.wu@gmail.com</a>> wrote:<br class=""></blockquote><div class=""><blockquote type="cite" class=""><br class=""><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;" class="">On Fri, Aug 26, 2016 at 2:34 PM, Charles Srstka<span class=""> </span></span><span dir="ltr" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;" class=""><<a href="mailto:cocoadev@charlessoft.com" target="_blank" class="">cocoadev@charlessoft.<wbr class="">com</a>></span><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;" class=""><span class=""> </span></span><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;" class="">wrote:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;" class=""><blockquote class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div style="word-wrap: break-word;" class=""><span class=""><blockquote type="cite" class="">On Aug 26, 2016, at 2:29 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank" class="">xiaodi.wu@gmail.com</a>> wrote:<br class=""></blockquote><div class=""><blockquote type="cite" class=""><br class=""><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;" class="">I misread your example. You have to run the app *without compiling*; your two versions of the library have a compatible ABI. The Swift compiler won't compile your app code, so how's that an example of "working around" anything in the language?</div></div></blockquote></div><br class=""></span><div class="">It is an example of an override occurring without the “override” keyword, and a demonstration that the “override” keyword’s purpose is to indicate programmer intent rather than do anything to the actual generated machine code (otherwise, the override here wouldn’t have happened). Despite this, no one argues against the existence of the “override” keyword.</div></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;" class="">This is not an example of that at all. You can't get the Swift compiler to compile the code. Failure to use `override` is a compile-time error, and compile-time errors don't happen at runtime. Why are we talking about 'generated machine code'?</div></div></blockquote></div><br class=""></span><div class="">Exactly; compile-time errors are intended to enforce correct behavior on the part of the developer. Your objection, as I understand it, is that a type that declares a method, which another file retroactively conforms to a private protocol that the original type can’t see, can’t indicate conformance in its original declaration, and that this would, in some way, cause a practical problem. I am failing to see what the problem is:</div></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">We were discussing your option (3), which would mean that trivial refactoring would lead to a lack of compile-time errors even if no one ever used your proposed keyword, effectively making the keyword optional. You wrote: '<span style="font-size: 12.8px;" class="">I can work around the “override” keyword and override things without it, but that doesn’t mean that I think we should remove the “override” keyword.' This was surprising to me, because if it were possible to avoid using `override` without a compile-time error, I would indeed argue that we should remove the `override` keyword. However, </span>you gave an example where *not compiling* means you don't get a *compile-time error*, which is not a workaround at all.</div></div></blockquote></div><br class=""><div class="">We were talking about retroactive modeling, and the effects that adding things after the fact can have on previously-existing code. This was, I think, a pretty close analogue for classes. The original app compiles, the library compiles, the refactored library compiles.</div><div class=""><br class=""></div><div class="">If you want it all to compile at the same time, well, we’ve still got access to all the Objective-C runtime functions in Swift. One can also write the assembly by hand. Things like “override” aren’t security features; they’re there to help you do the right thing. If you’re deliberately trying to do the wrong thing, I don’t think that can strictly be prevented.</div><div class=""><br class=""></div><div class="">Charles</div><div class=""><br class=""></div></body></html>