Instance Method インスタンスメソッド

addObserver:forKeyPath:options:context:

Registers the observer object to receive KVO notifications for the key path relative to the object receiving this message.

Declaration 宣言 

- (void)addObserver:(NSObject *)observer 
         forKeyPath:(NSString *)keyPath 
            options:(NSKeyValueObservingOptions)options 
            context:(void *)context;

Parameters パラメータ

observer

The object to register for KVO notifications. KVO通知に登録するオブジェクト。 The observer must implement the key-value observing method observeValueForKeyPath:ofObject:change:context:.

keyPath

The key path, relative to the object receiving this message, of the property to observe. This value must not be nil.

options オプション

A combination of the NSKeyValueObservingOptions values that specifies what is included in observation notifications. For possible values, see NSKeyValueObservingOptions.

context

Arbitrary data that is passed to observer in observeValueForKeyPath:ofObject:change:context:.

Discussion 解説

Neither the object receiving this message, nor observer, are retained. An object that calls this method must also eventually call either the removeObserver:forKeyPath: or removeObserver:forKeyPath:context: method to unregister the observer when participating in KVO.

See Also 参照

Registering for Observation

- removeObserver:forKeyPath:
Stops the observer object from receiving change notifications for the property specified by the key path relative to the object receiving this message.
- removeObserver:forKeyPath:context:
Stops the observer object from receiving change notifications for the property specified by the key path relative to the object receiving this message, given the context.