What is an NSCFDictionary?

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NSDictionary and the other collection classes are actually class clusters: several concrete subclasses classes masquerading under the interface of a single class: they all provide the same functionality (because they are subclasses of the same class — in NSDictionary’s case, this involves the three “primitive methods” -count, -objectForKey:, and -keyEnumerator), but have different internal workings to be efficient in different situations, based on how they’re created and what type of data they may be storing.

NSCFDictionary is simply a concrete subclass of NSDictionary. That is, your NSDictionaries may actually be NSCFDictionary instances, but you should treat them as instances of NSDictionary, because that will provide you with the required dictionary-storage functionality.

NSDictionary *value = [dict objectForKey:key];

Now, another reason your code doesn’t work: NSURLProtectionSpace is a class, so you should use it as a pointer, like this:

for (NSURLProtectionSpace *key ...

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