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 

func addObserver(_ observer: NSObject, 
      forKeyPath keyPath: String, 
         options: NSKeyValueObservingOptions = [], 
         context: UnsafeMutableRawPointer?)

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 observeValue(forKeyPath:of: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 observeValue(forKeyPath:of: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

func removeObserver(NSObject, forKeyPath: String)
Stops the observer object from receiving change notifications for the property specified by the key path relative to the object receiving this message.
func removeObserver(NSObject, forKeyPath: String, context: UnsafeMutableRawPointer?)
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.