<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">If a class partially implemented a protocol, it also would not be instantiatable, but a subclass can supply the missing method(s). Doesn’t the compiler already handle that? How are abstract classes harder?<br><br><div id="AppleMailSignature"><div>C. Keith Ray</div><div><a href="https://leanpub.com/wepntk" style="background-color: rgba(255, 255, 255, 0); font-size: 13pt;">https://leanpub.com/wepntk</a><span style="background-color: rgba(255, 255, 255, 0); font-size: 13pt;"> <- buy my book?</span></div><div><a href="http://agilesolutionspace.blogspot.com/">http://agilesolutionspace.blogspot.com/</a></div><div>twitter: @ckeithray</div><div><a href="http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf">http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf</a></div></div><div><br>On Nov 2, 2017, at 2:22 PM, Slava Pestov <<a href="mailto:spestov@apple.com">spestov@apple.com</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html; charset=utf-8">Abstract methods and classes seem like they will introduce a fair amount of complexity in the type checker, particularly around metatypes and constructors, because now we have this new concept of a class that cannot be directly instantiated. I’m not sure the cost is worth the benefit.<div class=""><br class=""></div><div class="">Slava<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Nov 2, 2017, at 12:45 PM, C. Keith Ray via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">How many "subclass must override" assertions or comments in base class methods do we need to see, to want to add "abstract" to the Swift language? 5? 50? 500?<div class=""><br class=""></div><div class="">It's a not uncommon idiom in Objective-C.<br class=""></div><div class=""><br class=""></div><div class="">I'm about to port a substantial amount of C++ code to swift, and compiler help to enforce abstract classes would be very useful.</div><div class=""><br class=""></div><div class=""><div class=""><br class="webkit-block-placeholder"></div><div class="">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="font-family: "Lucida Grande"; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">--<br class="">C. Keith Ray<br class="">Senior Software Engineer / Trainer / Agile Coach<br class="">* <a href="http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf" class="">http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf</a><br class=""></div><div style="font-family: "Lucida Grande"; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div></div><br class="Apple-interchange-newline">
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