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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>I kinda feel this is somehow related: <a href="http://discourse.natecook.com/t/pitch-return-a-subclass-for-a-protocol-method-without-the-need-for-an-associatedtype/2355">http://discourse.natecook.com/t/pitch-return-a-subclass-for-a-protocol-method-without-the-need-for-an-associatedtype/2355</a></p>
<p>It would be really handy to be able to override any type <code>A</code> with another type <code>B</code> where the relationship is <code>B : A</code>.</p>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1489148114107127040" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 10. März 2017 um 13:08:37, Rod Brown via swift-evolution (<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>Hi everyone. I found something odd that seems baked into how Cocoa Touch does protocols, but Swift cannot model it:<br><br><br>@interface UIScrollView: UIView<br><br>@property (weak, nonatomic) id <UIScrollViewDelegate> delegate;<br><br>@end<br><br>@interface UITableView: UIScrollView<br><br>@property (weak, nonatomic) id <UITableViewDelegate> delegate;<br><br>@end<br><br>@protocol UITableViewDelegate: UIScrollViewDelegate<br>...<br>@end<br><br><br><br>Subclasses can further specify the conformance of a property’s protocol-conforming object to state a further type on that property. I tried to do something extremely similar today in Swift, and it failed, saying the protocols were different:<br><br><br>class SourceBar: UIScrollView {<br> <br> override var delegate: SourceBarDelegate? {<br> get { return super.delegate as? SourceBarDelegate }<br> set { super.delegate = newValue }<br> }<br><br>} <br><br><br>@objc protocol SourceBarDelegate: UIScrollViewDelegate {<br> func foo()<br>}<br><br><br>Considering the fact that the protocol SourceBarDelegate conforms to UIScrollViewDelegate, I can’t see why this override should fail. Can anyone enlighten me as to why this is a limitation in the language?<br><br>Thanks,<br><br>Rod<br>_______________________________________________<br>swift-evolution mailing list<br>swift-evolution@swift.org<br>https://lists.swift.org/mailman/listinfo/swift-evolution<br></div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>