blocks|key|4513299|text|我只是由于不同的原因偶然发现了同样的问题，并想在这里将其发布给其他经历相同无用错误消息的人。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4513300|覆盖扩展中定义的计算变量的最后一个类也会导致此错误。不过，它适用于函数，因此看起来像是一个编译器错误。|4513301|//+at+line+0:+a+declaration+cannot+be+both+'final'+and+'dynamic'

import+UIKit

extension+UIViewController+{
++++var+test:+Int+{+return+0+}
}

final+class+TestController:+UIViewController+{
++++override+var+test:+Int+{+return+1+}
}|code-block|syntax|javascript|4513302|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I just stumbled over the same issue with a different cause and would like to post it here for other people experiencing the same useless error message.

A final class which overrides a computed variable defined in an extension also causes this error. It works for functions though and thus looks like a compiler bug.

<pre><code>// at line 0: a declaration cannot be both 'final' and 'dynamic'

import UIKit

extension UIViewController {
 var test: Int { return 0 }
}

final class TestController: UIViewController {
 override var test: Int { return 1 }
}
</code></pre>

blocks|key|5839|text|我通过将静态声明移动到我在扩展中定义的新结构中解决了这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5840|因此，不是这样：|5841|extension+NSOperationQueue+{
++++static+var+parsingQueue+:+NSOperationQueue+=+{
++++++++let+queue+=+NSOperationQueue()
++++++++queue.maxConcurrentOperationCount+=+1
++++++++return+queue
++++++++}()
}|code-block|syntax|javascript|5842|我有这个：|5843|extension+NSOperationQueue+{++++++++
++++struct+Shared+{
++++++++static+var+parsingQueue+:+NSOperationQueue+=+{
++++++++++++let+queue+=+NSOperationQueue()
++++++++++++queue.maxConcurrentOperationCount+=+1
++++++++++++return+queue++++++++++++++++
++++++++++++}()
++++}
}|5844|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I solved this issue by moving the static declaration into the new struct I defined in the extension.

So instead of this:

<pre><code>extension NSOperationQueue {
 static var parsingQueue : NSOperationQueue = {
 let queue = NSOperationQueue()
 queue.maxConcurrentOperationCount = 1
 return queue
 }()
}
</code></pre>

I have this:

<pre><code>extension NSOperationQueue { 
 struct Shared {
 static var parsingQueue : NSOperationQueue = {
 let queue = NSOperationQueue()
 queue.maxConcurrentOperationCount = 1
 return queue 
 }()
 }
}
</code></pre>

blocks|key|5896|text|之所以会出现这个问题，是因为Swift试图为静态属性生成一个动态访问器，以实现Obj-C兼容性，因为该类继承自NSObject。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5897|如果你的项目只在Swift中，而不是使用var访问器，你可以通过Swift+2.0中的@nonobjc属性来避免这个问题：|5898|import+Foundation

class+AAA:+NSObject+{}
extension+AAA+{
++++@nonobjc+static+let+value+=+111
}|code-block|syntax|javascript|5899|entityMap^0|1J|8|0|K|3|17|8|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|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

This issue arises because Swift is trying to generate a dynamic accessor for the static property for Obj-C compatibility, since the class inherits from <code>NSObject</code>.

If your project is in Swift only, rather than using a <code>var</code> accessor you can avoid the issue via the <code>@nonobjc</code> attribute in Swift 2.0:

<pre><code>import Foundation

class AAA: NSObject {}
extension AAA {
 @nonobjc static let value = 111
}
</code></pre>

blocks|key|4513371|text|您可以将其标记为私有，以防止此错误。如果你想公开它，你可以把它包装在一个公共函数中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4513372|extension+AAA+{

++++private+static+let+value+=+111

++++public+func+getDatValue()+->+Int+{
++++++++return+AAA.value
++++}++++
}|code-block|syntax|javascript|4513373|在我的例子中，我只引用了扩展本身中的属性，所以没有必要公开它。|4513374|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|$]]

You can mark it as private to prevent this error. If you want to expose it, you can wrap it in a public function:

<pre><code>extension AAA {

 private static let value = 111

 public func getDatValue() -&gt; Int {
 return AAA.value
 } 
}
</code></pre>

In my case, I only referenced the property in the extension itself, so there was no need to expose it.

blocks|key|5954|text|作为对@Eonil's+answer的略微改进，get不是必需的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5955|static+var+value:+Int+{+return++111+}|code-block|syntax|javascript|5956|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/29814707/1035008^0|O|3|3|F|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

As a slight improvement over <a href="https://stackoverflow.com/a/29814707/1035008">@Eonil's answer</a>, the <code>get</code> not necessary:

<pre><code>static var value: Int { return 111 }
</code></pre>

The declaration of <code>value</code> below

<pre><code>import Foundation

class AAA: NSObject {
 func test2() {
 self.dynamicType
 }
}
extension AAA {
 static let value = 111
}
</code></pre>

causes the following compilation error

<pre><code>A declaration cannot be both 'final' and 'dynamic'
</code></pre>

Why does this happen, and how can I deal with this?

I am using Swift 1.2 (the version shipped within Xcode 6.3.1 6D1002)

A declaration cannot be both 'final' and 'dynamic' error in Swift 1.2

编译器

Swift

Xcode

下面的value声明import Foundationclass AAA: NSObject {    func test2() {        self.dynamicType    }}extension AAA {    static let value    =   111}导致以下编译错误A declara...

问在Swift 1.2中，声明不能同时是'final‘和'dynamic’错误
EN

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