<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 15 Nov 2016, at 12:22, Haravikk 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=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 15 Nov 2016, at 07:53, Rick Mann 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=""><div class=""><br class=""><blockquote type="cite" class="">On Nov 14, 2016, at 22:51 , Charlie Monroe via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">One major example is the NS/UITableViewDataSource or Delegate - there are many many methods that you don't need to implement, hence are optional.<br class=""><br class="">But I think that this was partially solved by default implementation of protocol methods, which pretty much does what you want...<br class=""></blockquote><br class="">I just realized I only responded to someone else, and not the whole list. It does, but it forces me to make the return value of the protocol method optional, so that the default implementation can return nil. <br class=""><br class="">In the end, I guess that's not so bad, since I'm not happy with the entire approach, but it'll do for now.<br class=""></div></div></blockquote></div><br class=""><div class="">What's different about having the method return nil vs being optional? You're attempting to call it either way, and presumably need some means of handling the return value, except in Swift it's all nice and explicit and easy to put in a conditional like:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>if let result = myObject.someOptionalMethod() { /* Do some stuff */ }</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>print(myObject.someOptionalStringMethod() ?? "")</font></div><div class=""><font face="Monaco" class=""><br class=""></font></div>And so-on. If you need a method to be both optional, and return a nilable result then you can use a double optional like so:<div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>if let result = myObject.someDoubleOptionalMethod() { // Method was implemented</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>if let value = result { // Method returned a value</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>/* Do some stuff */</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</font><br class=""><div class=""><br class=""></div><div class=""><br class=""></div><div class="">By defining the methods as returning an Optional and throwing in default implementations you can specify fewer, bigger protocols and make clear what the requirements really are, though personally given the choice I'd prefer a dozen smaller protocols that are absolutely explicit in what they do.</div></div><div class=""><br class=""></div><div class="">But yeah, I think the tools you need are all there already; maybe there's an argument to be made for allowing default return values on protocol methods, to reduce the boiler-plate?</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><br class=""></div><div>I think there is a difference between:</div><div><br class=""></div><div>- A method which returns an optional result, and</div><div>- An optional method which, if present, always returns a result</div><div><br class=""></div><div>Perhaps not so much of a difference at the usage site (it’s just a question of placing a ? for optional chaining), but semantically and when conforming to the protocol, they mean different things.</div><div><br class=""></div><div>- Karl</div><br class=""></body></html>