<html><head><meta http-equiv="Content-Type" content="text/html charset=gb2312"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">The first (current) choice is better in fact.</div><div class=""><br class=""></div><div class="">With try closure out of the scope, you could not tell exactly which statement would throw. </div><div class="">In your example, only `makeSandwich` would throw, so there is no need to mark `eatASandwich` with a `try`.</div><div class=""><br class=""></div><div class="">Current design follows minimal conception very well, you could get to know that only the `makeASandwich` would throw an error, which reduce a lot of noise when reading this code.</div><div class=""><br class=""></div><br class=""><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class="" style="font-family: helvetica, Arial; font-size: 13px; background-color: rgb(255, 255, 255); word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><font face="Helvetica" class=""><span style="color: rgb(81, 81, 81); font-family: Tahoma; font-size: 12px;" class="">Best regards.</span></font></div><div class="" style="font-family: helvetica, Arial; font-size: 13px; background-color: rgb(255, 255, 255); word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><font face="Helvetica" class="">---</font></div><div class="" style="font-size: 13px; background-color: rgb(255, 255, 255); font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><font color="#515151" face="Tahoma" class=""><span class="" style="font-size: 12px;"><span class="" style="line-height: 15px;">Sincerely,</span> <br class="" style="line-height: 15px;"><span class="name" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; vertical-align: baseline;">Wei Wang (王巍, @onevcat)<br class=""></span></span></font><a href="http://im.onevcat.com/" class="" style="font-family: Tahoma; font-size: 12px; background-color: inherit; color: rgb(65, 131, 196); text-decoration: none; margin: 0px; padding: 0px; border: 0px; outline: 0px; vertical-align: baseline;">im.onevcat.com</a></div></div></div>
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<br class=""><div><blockquote type="cite" class=""><div class="">在 2015年12月7日，下午11:30，Don Arnel via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> 写道：</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Is there a reason this format was adopted for error handling:<div class=""><ol class="code-lines" style="border: 0px; font-size: 14px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; counter-reset: li 0; line-height: 1.6em; list-style: none; font-family: Helvetica, Arial, sans-serif;"><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><br class=""></li></ol></div><div class=""><ol class="code-lines" style="border: 0px; font-size: 14px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; counter-reset: li 0; line-height: 1.6em; list-style: none; font-family: Helvetica, Arial, sans-serif;"><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"><span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">do</span> {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">try</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">makeASandwich</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">eatASandwich</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">} <span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">catch</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">Error</span>.<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">OutOfCleanDishes</span> {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">washDishes</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">} <span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">catch</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">Error</span>.<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">MissingIngredients</span>(<span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">let</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">ingredients</span>) {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">buyGroceries</span>(<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">ingredients</span>)</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">}</code></li></ol><div class=""><br class=""></div></div><div class="">rather than this format:</div><div class=""><br class=""></div><div class=""><ol class="code-lines" style="border: 0px; font-size: 14px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; counter-reset: li 0; line-height: 1.6em; list-style: none; font-family: Helvetica, Arial, sans-serif;"><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"><span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">try</span> {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">makeASandwich</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">eatASandwich</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">} <span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">catch</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">Error</span>.<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">OutOfCleanDishes</span> {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -13px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">washDishes</span>()</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">} <span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">catch</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">Error</span>.<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">MissingIngredients</span>(<span class="kt" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(170, 51, 145);">let</span> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">ingredients</span>) {</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;"> <span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">buyGroceries</span>(<span class="vc" style="border: 0px; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; color: rgb(63, 110, 116);">ingredients</span>)</code></li><li style="border-width: 0px 0px 0px 18px; border-left-style: solid; border-left-color: transparent; margin: 0px; outline: 0px; padding: 0px 10px 0px 0px; vertical-align: baseline; text-indent: -17px; white-space: pre-wrap; list-style-type: none;" class=""><code class="code-voice" style="border: 0px; font-size: 0.85em; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline; font-family: Menlo, monospace; word-wrap: break-word;">}</code></li></ol><div class=""><br class=""></div></div><div class="">The second format is much more intuitive, and reads easier IMO.</div><div class=""><br class=""></div>
<img src="https://u2002410.ct.sendgrid.net/wf/open?upn=80FydpVXO1iznd7NlD1VGOniZKpUfBnbaLfoowjEmdTW8z0IN1Cv1LKOmSqFvQBMiybXV4oHhmaSb3i0ynt6N6A6BCloOljtUxHTMyyCmkOxboBkezXNHr0GWlw8Y1zCl4kXDTNAeJtV5rsNNm5MKR9RIToQAttvF8vmqqAa-2FMzVva9LTl7HcIVyZKjlbiJtm2oZ-2BKggv4Xg64bAINa7X-2FSkduWWfsXHcnTAdhwONKU-3D" alt="" width="1" height="1" border="0" style="height:1px !important;width:1px !important;border-width:0 !important;margin-top:0 !important;margin-bottom:0 !important;margin-right:0 !important;margin-left:0 !important;padding-top:0 !important;padding-bottom:0 !important;padding-right:0 !important;padding-left:0 !important;" class="">
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