<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">I'm always in favor of removing special cases (like lazy and willSet/didSet), so the idea of property behaviors itself is very appealing to me.<div class="">There's one downside, though:</div><div class="">The proposal makes some keywords obsolete, but introduces a whole bunch of new stuff in exchange — and all of this only can be used with properties…</div><div class=""><br class=""></div><div class="">I hope you agree with me that there is merit in keeping the language small (it's called "Swift", not "Turkey" ;-), and that the proposal would improve if it's possible to slim it down.</div><div class=""><br class=""></div><div class="">Imho the first step to add property behaviors should be refining how properties are modeled in Swift:</div><div class="">In many languages, properties are represented as a pair of methods (setter and getter), and their absence has several downsides (functional programming works best with functions ;-).</div><div class=""><br class=""></div><div class="">As soon as there is a way to read and write properties in a functional way, their behaviors could be expressed in a universal manner:</div><div class="">Afaics, all major use cases for behaviors can be implemented as simple "decorators" — in fact, I could simulate most examples from the proposal in a tiny playground (a part of it is attached).</div><div class="">Of course, the simulation is ugly, but I am confident that some nice ideas would come up if properties were more accessible.</div><div class=""><br class=""></div><div class="">Best regards,</div><div class="">Tino</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">//: Properties are modelled as a getter/setter pair</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">struct</span> Property<T> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> get: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Void</span> -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> set: (<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Void</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> Test {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>// A field to store the actual data</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> mValue: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span>?</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>// This is our "pseudo-property": Just imaging that `self.value.get` maps to `self.value`</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> value = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">0</span> }, set: { Int <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span> } )</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">init</span>() {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>// This is necessary because we need `self` to fake the getter/setter</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span> = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">mValue</span>! }, set: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">mValue</span> = $0 })</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">/*:</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">Behaviors are modelled as a transformation:</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">The take a set of functions and return another set the is extended according to the behavior.</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0); min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">A real implementation would gain more clarity from the (deprecated...) currying-syntax</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">*/</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> didSetBehavior<T>(property: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>>, didSet: (<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Void</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> setter(value: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">set</span>(value)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>didSet(value)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">get</span>, set: <span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">setter</span>)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> DidSet: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Test</span> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">//: Imagine we have no superclass, and `value` is declared like</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">/*:</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>var[didSetBehavior {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>print("New value is \($0)")</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}] value: Int</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class="">*/</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>override<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">() {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>super<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">()</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(49, 89, 93);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> = </span>didSetBehavior<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">) {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(209, 47, 27);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>"New value is <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">$0</span>)"<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> willSetBehavior<T>(property: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>>)(allow: (old: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>, new: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Bool</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> setter(new: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">if</span> allow(old: property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">get</span>(), new: new) {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">set</span>(new)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">get</span>, set: <span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">setter</span>)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> WillSet: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Test</span> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>override<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">() {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>super<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">()</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span> = <span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">willSetBehavior</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span>)(allow: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> $0 != $1 } )</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> WillSetDidSet: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">WillSet</span> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>override<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">() {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>super<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>init<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">()</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(49, 89, 93);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> = </span>didSetBehavior<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">) {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(209, 47, 27);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>"New value is <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">$0</span>)"<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div></div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> copyBehavior<T: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">NSCopying</span>>(property: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> performCopy(value: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span>) {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> copy = value.<span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">copyWithZone</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">nil</span>) <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span>! <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">set</span>(copy)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: property.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">get</span>, set: <span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">performCopy</span>)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> Copy {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> mValue = <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">NSString</span>()</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> value = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">NSString</span>() }, set: { NSString <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> } )</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">init</span>() {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span> = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Property</span>(get: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">mValue</span> }, set: { <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">mValue</span> = $0 })</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(49, 89, 93);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> = </span>copyBehavior<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">value</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> copyTest = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Copy</span>()</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(79, 129, 135);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>copyTest<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>value<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>get<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">())</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> mutableString = <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">NSMutableString</span>(string: <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"Mutable"</span>)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(79, 129, 135);" class="">copyTest<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>value<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>set<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>mutableString<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(79, 129, 135);" class="">mutableString<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">appendString</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">" string"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(79, 129, 135);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>copyTest<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>value<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span>get<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">())</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> decorate<In, Out, Discard>(function: (<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">In</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Out</span>, decoration: (<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">In</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Discard</span>) -> (<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">In</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Out</span> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> result(input: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">In</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Out</span> {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>decoration(input)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> function(input)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span>return<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">result</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> FuncTest {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> f = { (input: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span>) <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span>(input)</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">init</span>() {</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">f</span> = <span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">decorate</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">f</span>) { input <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(209, 47, 27);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><span class="Apple-tab-span" style="white-space:pre"> </span></span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>"Our input is <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span>(<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">input</span>)"<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">}</div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(209, 47, 27);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">FuncTest</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">().</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">f</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span>"duplicated"<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div></div><div class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""><br class=""></span></div></body></html>