<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">If memory serves: the CLOS Metaobject Protocol had features like this. This might be good read if you are considering writing a proposal for this. (Dylan Lives! :) )</div><div class=""><br class=""></div><div class=""><a href="https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Protocol" class="">https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Protocol</a></div><div class=""><br class=""></div><div class="">As I remember, these sorts of features did have scalability issues.</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On Nov 17, 2016, at 3:54 AM, Tino Heth 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="">An equivalent of "NS_REQUIRES_SUPER" (hopefully with a better name ;-) has been requested several times, but never got the momentum it deserves.<div class="">Considering the current confusion (especially in UIKit), it would be really nice to have some help from the compiler, and I wonder how composition and protocols would be helpful here at all.</div><div class=""><br class=""></div><div class="">I guess the problem is that there are to many options for this feature without an obvious favorite: Not only for the keywords, but also for the exact semantic.</div><div class=""><br class=""></div><div class="">Additionally, there are imho already to many access levels (private, fileprivate, internal, public, <i class="">extendable?</i>, open), so I hope we'll someday find a solution that is powerful enough to replace the special willSet/didSet treatment for properties as well.</div><div class=""><br class=""></div><div class="">So unless somebody has a real flash of genius, I guess it's better to delay discussion until there is a chance for new proposals to be accepted.</div><div class=""><br class=""></div><div class="">Tino</div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></blockquote></div><br class=""></body></html>