无法使用'class'作为NSDictionary中的键 [英] Unable to use 'class' as a key in NSDictionary

问题描述

我想在 NSDictionary 中使用类作为键。我查看了此问题的答案，我所拥有的几乎是相同;我使用 setObject：forKey：。然而，XCode抱怨说，不兼容的指针类型发送类'id< NSCopying>'的参数类'。我的调用是：

I'm trying to use a class as a key in an NSDictionary. I looked at the answer to this question and what I have is pretty much the same; I'm using setObject: forKey:. However, XCode complains, saying Incompatible pointer types sending 'Class' to parameter of type 'id<NSCopying>'. The call I have is:

[_bugTypeToSerializerDictionary setObject: bugToStringSerializer 
                                forKey: [bugToStringSerializer serializedObjectType]];

bugToStringSerializer 是 BugToStringSerializer ，具体实现实现 serializedObjectType 。具体实现的示例如下：

bugToStringSerializer is an instance of BugToStringSerializer whose concrete implementations implement serializedObjectType. An example of a concrete implementation looks like this:

- (Class) serializedObjectType {
    return [InfectableBug class];
}

我在这里做什么？

推荐答案

（似乎类确实符合 NSCopying 不 c> id< NSCopying> 。）修改类不符合协议。当然重要的是类响应 copy 和 copyWithZone：消息（这就是为什么你可以安全地忽略警告）。它们的类型是仍然不是 id< NSCopying> 。）这就是为什么编译器抱怨。

(It seems that classes do conform to NSCopying, however their type is not id <NSCopying>.) classes do not conform to protocols. Of course the essential is that classes respond to the copy and copyWithZone: messages (and that's why you can safely ignore the warning in this case). Their type is still not id <NSCopying>.) That's why the compiler complains.

如果你真的不想要这种丑陋的警告，只需执行一个显式的类型转换：

If you really don't want that ugly warning, just perform an explicit type conversion:

[dictionary setObject:object forKey:(id <NSCopying>)someClass];

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