質問

The method discussion for setValue:forKeyPath: in Apple's NSKeyValueCoding Protocol documentation starts with:

The default implementation of this method [...]

Now, this might just be me getting caught with semantics but:

  1. How can an Objective-C Protocol have a default implementation?
  2. Since NSObject doesn't appear to conform to this protocol, how would one be able to take advantage of this default implementation in their own NSObject subclasses?
役に立ちましたか?

解決

NSKeyValueCoding is an informal protocol, which means it's implemented as a category (in this case, on NSObject). The NSObject class provides the default implementation of the methods declared in the category.

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