シンプルで、モダンなkey value observingが行える メリット ブロックで書けるので、コードが読みやすくなる observerの削除のときにexceptionが起きない observerの削除はFBKVOControllerのdelloc時に呼ばれる 使い方 // create KVO controller with observer FBKVOController *KVOController = [FBKVOController controllerWithObserver:self]; // observe clock date property [KVOController observe:clock keyPath:@"date" options:NSKeyValueObservingOptionInitial|NSKeyValueObservingOptionNe
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