<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 23, 2016, at 12:11 AM, Charlie Monroe <<a href="mailto:charlie@charliemonroe.net" class="">charlie@charliemonroe.net</a>> wrote:<br class=""></blockquote><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div class="" 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;">I don't see it as sub-par in this example (this actually happened to me):</div><div class="" 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;"><br class=""></div><div class="" 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;">@objc protocol Foo {</div><div class="" 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;"><span class="Apple-tab-span" style="white-space: pre;"> </span>optional func bar()</div><div class="" 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;">}</div><div class="" 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;"><br class=""></div><div class="" 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 FooImpl: Foo {</div><div class="" 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;"><span class="Apple-tab-span" style="white-space: pre;"> </span>func bar() { ... }</div><div class="" 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;">}</div><div class="" 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;"><br class=""></div><div class="" 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;">Now imagine that bar() gets renamed in the protocol to baz(). You get no warnings, nothing - since the bar() was optional (or can have default implementation as Chalers mentioned). FooImpl still conforms to Foo and bar() can live on there happily.</div></div></blockquote></div><br class=""><div class="">Had that happen to me a bunch of times, especially when I realize that the method needs to have one more argument and then forget to add it everywhere (which is harder to use search-and-replace for, as well).</div><div class=""><br class=""></div><div class="">Here’s another case where this can bite you:</div><div class=""><br class=""></div><div class="">In file P.swift:</div><div class=""><br class=""></div><div class="">protocol P {</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func foo()</div><div class="">}</div><div class=""><br class=""></div><div class="">extension P {</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func foo()</div><div class="">}</div><div class=""><br class=""></div><div class="">In another file, S.swift:</div><div class=""><br class=""></div><div class="">struct S: P {}</div><div class=""><br class=""></div><div class="">Imagine I rename foo in the protocol, but forget to rename it in the extension. The method no longer has a default implementation, and we do indeed get an error, but the error’s in S.swift, in the wrong place. S complains that it doesn’t conform to the protocol. If there were a keyword on foo() in the extension, the compiler warning would be right where the problem is as soon as I renamed the method in the protocol, and it’d be a 2-second fix.</div><div class=""><br class=""></div><div class="">Charles</div><div class=""><br class=""></div></body></html>