Indicates the key of the attribute that changed. Used as a key in the userInfo dictionary passed to QTCaptureDeviceAttributeWillChangeNotification, and QTCaptureDeviceAttributeDidChangeNotification to indicate the key of the attribute that changed.
Available in Mac OS X v10.5 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)