NSUndoManager.Notifications.ObserveWillUndoChange Method

Definition

Namespace:

Foundation

Assembly:

Xamarin.iOS.dll

Overloads

ObserveWillUndoChange(EventHandler<NSNotificationEventArgs>)	Strongly typed notification for the WillUndoChangeNotification constant.
ObserveWillUndoChange(NSObject, EventHandler<NSNotificationEventArgs>)	Strongly typed notification for the WillUndoChangeNotification constant.

ObserveWillUndoChange(EventHandler<NSNotificationEventArgs>)

Strongly typed notification for the WillUndoChangeNotification constant.

public static Foundation.NSObject ObserveWillUndoChange (EventHandler<Foundation.NSNotificationEventArgs> handler);

static member ObserveWillUndoChange : EventHandler<Foundation.NSNotificationEventArgs> -> Foundation.NSObject

Parameters

handler

EventHandler<NSNotificationEventArgs>

Method to invoke when the notification is posted.

Returns

NSObject

Token object that can be used to stop receiving notifications by either disposing it or passing it to RemoveObservers(IEnumerable<NSObject>)

Remarks

The following example shows how you can use this method in your code

//
// Lambda style
//

// listening
notification = NSUndoManager.Notifications.ObserveWillUndoChange ((sender, args) => {
    /* Access strongly typed args */
    Console.WriteLine ("Notification: {0}", args.Notification);
});

// To stop listening:
notification.Dispose ();

//
//Method style
//
NSObject notification;
void Callback (object sender, Foundation.NSNotificationEventArgs args)
{
    // Access strongly typed args
    Console.WriteLine ("Notification: {0}", args.Notification);
}

void Setup ()
{
    notification = NSUndoManager.Notifications.ObserveWillUndoChange (Callback);
}

void Teardown ()
{
    notification.Dispose ();
}

ObserveWillUndoChange(NSObject, EventHandler<NSNotificationEventArgs>)

Strongly typed notification for the WillUndoChangeNotification constant.

public static Foundation.NSObject ObserveWillUndoChange (Foundation.NSObject objectToObserve, EventHandler<Foundation.NSNotificationEventArgs> handler);

static member ObserveWillUndoChange : Foundation.NSObject * EventHandler<Foundation.NSNotificationEventArgs> -> Foundation.NSObject

Parameters

objectToObserve

NSObject

The object to observe.

handler

EventHandler<NSNotificationEventArgs>

Method to invoke when the notification is posted.

Returns

NSObject

Token object that can be used to stop receiving notifications by either disposing it or passing it to RemoveObservers(IEnumerable<NSObject>)

Remarks

This method can be used to subscribe for WillUndoChangeNotification notifications.

// Listen to all notifications posted for any object
var token = NSUndoManager.Notifications.ObserveWillUndoChange ((notification) => {
	Console.WriteLine ("Observed WillUndoChangeNotification!");
};

// Listen to all notifications posted for a single object
var token = NSUndoManager.Notifications.ObserveWillUndoChange (objectToObserve, (notification) => {
	Console.WriteLine ($"Observed WillUndoChangeNotification for {nameof (objectToObserve)}!");
};

// Stop listening for notifications
token.Dispose ();