<div dir="ltr"><div class="gmail_default" style="font-family:georgia,serif"><span style="font-family:arial,sans-serif;font-size:12.800000190734863px">Wagner, the `extension` of `protocol` is never dynamic. It is `fail safe`. It means if you don't implement something, the compiler will use the implementation in the `protocol extension`. As in swift, struct and enum can also conform protocols.</span><br></div><div class="gmail_default" style="font-family:georgia,serif"><span style="font-family:arial,sans-serif;font-size:12.800000190734863px"><br></span></div><div class="gmail_default" style="font-family:georgia,serif"><span style="font-family:arial,sans-serif;font-size:12.800000190734863px">If you want the other way, you should do it in a base class, not in a protocol extension.</span></div><div class="gmail_default" style="font-family:georgia,serif"><span style="font-family:arial,sans-serif;font-size:12.800000190734863px"><br></span></div><div class="gmail_default" style="font-family:georgia,serif"><span style="font-family:arial,sans-serif;font-size:12.800000190734863px">Zhaoxin</span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jan 24, 2017 at 4:32 AM, Wagner Truppel via swift-users <span dir="ltr"><<a href="mailto:swift-users@swift.org" target="_blank">swift-users@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><span class=""><div></div><blockquote type="cite"><div><font color="#000000"><span style="background-color:rgba(255,255,255,0)">On 23 Jan 2017, at 19:56, Slava Pestov <<a href="mailto:spestov@apple.com" target="_blank">spestov@apple.com</a>> wrote:<br><br></span></font></div><blockquote type="cite"><blockquote type="cite"><font color="#000000"><span style="background-color:rgba(255,255,255,0)">class B: A {</span></font></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"></blockquote><blockquote type="cite"><font color="#000000"><span style="background-color:rgba(255,255,255,0)"> var item: String { // subclass specialises 'item' by "overriding" the protocol extension implementation<br></span></font></blockquote><font color="#000000"><span style="background-color:rgba(255,255,255,0)"><br>This is the problem. You’re not overriding the protocol extension version, you’re just shadowing it for the purposes of compile-time name lookup. Note that if you add the ‘override’ keyword here, the compiler complains because there’s nothing in the base class to override.</span></font></blockquote></blockquote><br></span><div>Yes, that's why I wrote overriding in quotes and also why I tried to use the word specialise in place of override. My beef is not really here; this really was just a preamble. My issue is with the fact that adding the declaration to the protocol doesn't solve the problem despite the fact that the property is then supposed to be dynamically dispatched but isn't.</div></div><br>______________________________<wbr>_________________<br>
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