<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="">Hi there!<div class=""><br class=""></div><div class="">the Swift book says:</div><div class=""><br class=""></div><div class="">> Extensions in Swift can:<br class="">> <br class=""><div class="">> • Add computed instance properties and computed type properties<br class=""></div><div class="">> • Define instance methods and type methods<br class=""></div><div class="">> • Provide new initializers<br class=""></div><div class="">> • Define subscripts<br class=""></div><div class="">> • Define and use new nested types<br class=""></div><div class="">> • Make an existing type conform to a protocol</div></div><div class="">> </div><div class="">> NOTE<br class="">> Extensions can add new functionality to a type, but they cannot override existing functionality.</div><div class=""><br class=""></div><div class="">However, in practice we can override methods in class extensions:</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="">class</span><span style="font-variant-ligatures: no-common-ligatures" class=""> ViewController: </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">UIViewController</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {}</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span><br class=""></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: #bb2ca2" class="">extension</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">ViewController</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 style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">override</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> viewDidLoad() {}</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal;" class="">This seems to be incompatible with what the book claims:</div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class="">> … cannot override existing functionality ...</div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class="">So, my questions are:</div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class="">• Why are overrides allowed in class extensions?</div><div style="margin: 0px; line-height: normal;" class="">• Am I reading the book wrong? :)</div></div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class="">R+</div></body></html>