<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=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""><div style="color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class="">I'd prefer to see block-scoped synchronization rather than whole-method-only; it gives much more flexibility.</span></div><div style="color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""><br class=""></span></div><div style="color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class="">Note that you can use the objc synchronization feature with reference types:</span></div><div class=""><br class=""></div></span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">// Or (_ obj:...) if you prefer the label-less objc style)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> synchronized(on obj: </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">AnyObject</span><span style="font-variant-ligatures: no-common-ligatures" class="">, do block: () </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">throws</span><span style="font-variant-ligatures: no-common-ligatures" class=""> -> </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Void</span><span style="font-variant-ligatures: no-common-ligatures" class="">) </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">rethrows</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; line-height: normal; color: rgb(62, 30, 129);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">objc_sync_enter</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(obj)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">defer</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; line-height: normal; color: rgb(62, 30, 129);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">objc_sync_exit</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(obj)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">try</span><span style="font-variant-ligatures: no-common-ligatures" class=""> block()</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal; color: rgb(49, 89, 93);" class=""><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">// or synchronized(self)</span></div><div style="margin: 0px; line-height: normal; color: rgb(49, 89, 93);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">synchronized</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(on: </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">) {</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// do something</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div><div style="margin: 0px; line-height: normal; color: rgb(49, 89, 93);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">try</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">synchronized</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(on: </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">) {</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">throw</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">NSError</span><span style="font-variant-ligatures: no-common-ligatures" class="">()</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div><div style="margin: 0px; line-height: normal; color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">Not 100% sure this works with bridged reference types (e.g. Array); definitely doesn't work with Int. Use a dummy NSObject() if needed.</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div><div class="">That said, I'd love to see a swift-native solution that works with value types (and doesn't rely on the objc runtime).</div><div class=""><br class=""></div></div><div><blockquote type="cite" class=""><div class="">On Jun 12, 2017, at 2:10 AM, Erik Aigner via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><div class="">[...]<br class="">With synchronized attribute (the semaphore/wait/deferred-signal is synthesized by Swift automatically)<br class=""><br class="">class Obj {<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>synchronized func method() {<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>// semaphore is synthesized automatically, do something…<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}<br class="">}<br class=""><br class=""></div></div></blockquote></div><br class=""></body></html>