<html><head><style>
body {
font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
padding:1em;
margin:auto;
background:#fefefe;
}
h1, h2, h3, h4, h5, h6 {
font-weight: bold;
}
h1 {
color: #000000;
font-size: 28pt;
}
h2 {
border-bottom: 1px solid #CCCCCC;
color: #000000;
font-size: 24px;
}
h3 {
font-size: 18px;
}
h4 {
font-size: 16px;
}
h5 {
font-size: 14px;
}
h6 {
color: #777777;
background-color: inherit;
font-size: 14px;
}
hr {
height: 0.2em;
border: 0;
color: #CCCCCC;
background-color: #CCCCCC;
display: inherit;
}
p, blockquote, ul, ol, dl, li, table, pre {
margin: 15px 0;
}
a, a:visited {
color: #4183C4;
background-color: inherit;
text-decoration: none;
}
#message {
border-radius: 6px;
border: 1px solid #ccc;
display:block;
width:100%;
height:60px;
margin:6px 0px;
}
button, #ws {
font-size: 12 pt;
padding: 4px 6px;
border-radius: 5px;
border: 1px solid #bbb;
background-color: #eee;
}
code, pre, #ws, #message {
font-family: Monaco;
font-size: 10pt;
border-radius: 3px;
background-color: #F8F8F8;
color: inherit;
}
code {
border: 1px solid #EAEAEA;
margin: 0 2px;
padding: 0 5px;
}
pre {
border: 1px solid #CCCCCC;
overflow: auto;
padding: 4px 8px;
}
pre > code {
border: 0;
margin: 0;
padding: 0;
}
#ws { background-color: #f8f8f8; }
.bloop_markdown table {
border-collapse: collapse;
font-family: Helvetica, arial, freesans, clean, sans-serif;
color: rgb(51, 51, 51);
font-size: 15px; line-height: 25px;
padding: 0; }
.bloop_markdown table tr {
border-top: 1px solid #cccccc;
background-color: white;
margin: 0;
padding: 0; }
.bloop_markdown table tr:nth-child(2n) {
background-color: #f8f8f8; }
.bloop_markdown table tr th {
font-weight: bold;
border: 1px solid #cccccc;
margin: 0;
padding: 6px 13px; }
.bloop_markdown table tr td {
border: 1px solid #cccccc;
margin: 0;
padding: 6px 13px; }
.bloop_markdown table tr th :first-child, table tr td :first-child {
margin-top: 0; }
.bloop_markdown table tr th :last-child, table tr td :last-child {
margin-bottom: 0; }
.bloop_markdown blockquote{
border-left: 4px solid #dddddd;
padding: 0 15px;
color: #777777; }
blockquote > :first-child {
margin-top: 0; }
blockquote > :last-child {
margin-bottom: 0; }
code, pre, #ws, #message {
word-break: normal;
word-wrap: normal;
}
hr {
display: inherit;
}
.bloop_markdown :first-child {
-webkit-margin-before: 0;
}
code, pre, #ws, #message {
font-family: Menlo, Consolas, Liberation Mono, Courier, monospace;
}
.send { color:#77bb77; }
.server { color:#7799bb; }
.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>Protocols solve way more problems than this. Sometimes they are used as backdoors to existing APIs as well. It’s simply an implementation artifact that such a protocol might end up public, but there is no point to allow the client to conform to it.</p>
<p>I also showed a concrete example in the discussion thread where I needed a <code>public-but-not-open</code> protocol really badly. ;)</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_1487454980036779008" 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 18. Februar 2017 um 22:45:00, Charles Srstka 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 style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div></div><div>
<title></title>
<blockquote type="cite" class="">On Feb 18, 2017, at 2:41 PM,
Matthew Johnson via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></blockquote>
<div>
<blockquote type="cite" class=""><br class="Apple-interchange-newline">
<div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; 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; float: none; display: inline !important;" class="">There are good reasons a library may not wish to allow
users to add conformances to a protocol. For example, it may
not wish to expose the conforming concrete types. While
similar behavior could be accomplished with an enum if cases could
be private, that requires an implementation to use switch
statements rather than polymorphism.</span></div>
</blockquote>
</div>
<br class="">
<div class="">Uh, what? You can expose protocols without exposing
the concrete types that conform to them. That’s kind of the whole
point of protocols.</div>
<div class=""><br class=""></div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">public</span> <span style="font-variant-ligatures: no-common-ligatures" class="">protocol</span> <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">P {}</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(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">private</span> <span style="font-variant-ligatures: no-common-ligatures" class="">struct</span> <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">S:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">P</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; min-height: 13px;" class=""><br class=""></div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">public</span> <span style="font-variant-ligatures: no-common-ligatures" class="">var</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">p:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">P</span></div>
</div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class=""><br class=""></span></div>
<div style="margin: 0px; line-height: normal;" class="">reduces to
this interface:</div>
<div style="margin: 0px; line-height: normal;" class=""><br class=""></div>
<div style="margin: 0px; line-height: normal;" class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">public</span> <span style="font-variant-ligatures: no-common-ligatures" class="">protocol</span> <span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">P {</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 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(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">public</span> <span style="font-variant-ligatures: no-common-ligatures" class="">var</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">p:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">P</span></div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class=""><br class=""></span></div>
<div style="margin: 0px; line-height: normal;" class="">The library
can then assign something of type S to the “p” variable, and
clients will be able to use it without having access to its
concrete type.</div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class=""><br class=""></span></div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class="">Charles</span></div>
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class=""><br class=""></span></div>
</div>
_______________________________________________<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>