The key path, relative to object, to the value that has changed.
Instance Method
インスタンスメソッド
observe
observeValue(forKeyPath:of:change:context:)
Informs the observing object when the value at the specified key path relative to the observed object has changed.
Availability
- iOS 2.0+
- iPadOS 2.0+
- macOS 10.3+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
Technology
- Foundation ファウンデーション
Declaration 宣言
func observeValue(forKeyPath keyPath: String?,
of object: Any?,
change: [NSKeyValueChangeKey : Any]?,
context: UnsafeMutableRawPointer ?)
Parameters パラメータ
keyPathobjectThe source object of the key path
key.Path changeA dictionary that describes the changes that have been made to the value of the property at the key path
keyrelative toPath object. Entries are described inChange Dictionary Keys.contextThe value that was provided when the observer was registered to receive key-value observation notifications.
Discussion 解説
For an object to begin sending change notification messages for the value at key, you send it an add message, naming the observing object that should receive the messages. When you are done observing, and in particular before the observing object is deallocated, you send the observed object a remove or remove message to unregister the observer, and stop sending change notification messages.