blocks|key|160034|text|protocol+AddsMoreCommands:+class+{
++++//+Code
}

extension+AddsMoreCommands+where+Self:+UIViewController+{
++++//+Code
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|160035|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>protocol AddsMoreCommands: class {
 // Code
}

extension AddsMoreCommands where Self: UIViewController {
 // Code
}
</code></pre>

blocks|key|160058|text|这也可以在没有扩展的情况下实现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|160059|protocol+AddsMoreCommands:+UIViewController+{
++++//+code
}|code-block|syntax|javascript|160060|与以下内容完全相同：|160061|protocol+AddsMoreCommands+where+Self:+UIViewController+{
+++//+code
}|160062|我通常使用第一个选项，我不久前在Swift文档上看到的IIRC，这是当约束是Self时的推荐方式，如果是其他约束，比如关联类型，则可以使用where。|offset|length|style|CODE|160063|注意，由于UIViewController也是class，所以可以为弱属性(如委托)实现此协议。|160064|编辑的2021/01/05：以前发布的解决方案有一个警告，我已经删除它，并使用这个不产生任何警告。|BOLD|160065|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.swift.org/swift-book/LanguageGuide/Protocols.html^0|0|0|0|0|12|4|1X|5|1N|4|0|0|5|G|N|5|0|0|D|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|15|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|17|8|@$M|18|N|19|O|P]|$M|1A|N|1B|O|P]]|9|@$M|1C|N|1D|1|1E]]|A|$]]|$1|Q|3|R|5|6|7|1F|8|@$M|1G|N|1H|O|P]|$M|1I|N|1J|O|P]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1K|8|@$M|1L|N|1M|O|U]]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]]|W|$X|$5|Y|Z|10|A|$11|12]]]]

This can also be achieved without an extension:
<pre><code>protocol AddsMoreCommands: UIViewController {
 // code
}
</code></pre>
Which is exactly the same as:
<pre><code>protocol AddsMoreCommands where Self: UIViewController {
 // code
}
</code></pre>
I usually use the first option, IIRC I read a while ago on the Swift docs that that is the recomended way when the constraint is <code>Self</code>, if is other constraint such as <a href="https://docs.swift.org/swift-book/LanguageGuide/Protocols.html" rel="noreferrer">associate types</a> is when <code>where</code> can be used.
Notice that since <code>UIViewController</code> is a <code>class</code> too, this protocol can be implemented for weak properties such as delegates.
EDITED 2021/01/05: Previous posted solution had a warning, I have removed it and use this one which does not produce any warning.

blocks|key|160084|text|由于上一份答复中的一个问题，我最后发表了以下声明：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|160085|protocol+AddsMoreCommands+where+Self+:+UIViewController+{+
++++//+protocol+stuff+here++
}|code-block|syntax|javascript|160086|Xcode+9.1中没有警告|160087|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Because of an issue in the previous answer I ended up with this declaration:

<pre><code>protocol AddsMoreCommands where Self : UIViewController { 
 // protocol stuff here 
}
</code></pre>

no warnings in Xcode 9.1

blocks|key|107476|text|现在，在Swift+5中，您可以通过以下方法实现这一点：|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|107477|protocol+AddsMoreCommands:+UIViewController+{
+++++/*+...+*/
}|code-block|syntax|javascript|107478|挺方便的。|107479|entityMap^0|4|7|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Now in Swift 5 you can achieve this by:

<pre><code>protocol AddsMoreCommands: UIViewController {
 /* ... */
}
</code></pre>

Quite handy.

I want this protocol:

<pre><code>protocol AddsMoreCommands {
 /* ... */
}
</code></pre>

only to be adopted by classes that inherit from the class <code>UIViewController</code>. <a href="https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html#//apple_ref/doc/uid/TP40014097-CH25-ID267">This page</a> tells me I can specify that it is only adopted by a class (as opposed to a struct) by writing

<pre><code>protocol AddsMoreCommands: class {
}
</code></pre>

but I cannot see how to require that it is only adopted by a particular class. <a href="https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html#//apple_ref/doc/uid/TP40014097-CH25-ID267">That page later</a> talks about adding <code>where</code> clauses to protocol extensions to check conformance but I cannot see how to adapt that either.

<pre><code>extension AddsMoreCommands where /* what */ {
}
</code></pre>

Is there a way to do this?
Thanks!

How to require that a protocol can only be adopted by a specific class

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我要这个协议：protocol AddsMoreCommands {     /* ... */}只能由继承自类UIViewController的类采用。告诉我，我只能通过编写类(而不是结构)来指定它。protocol AddsMoreCommands: class {}但是，我看不出如何要求它只为某一阶层所采用。讨论...

问如何要求协议只能由特定类采用
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何要求协议只能由特定类采用EN