mccallum@gnu.ai.mit.edu
)rfm@gnu.org
)richard@brainstorm.co.uk
)Date: 2006-02-11 11:22:57 -0700 (Sat, 11 Feb 2006)
Copyright: (C) 1996,1999 Free Software Foundation, Inc.
- Declared in:
- Foundation/NSNotification.h
- Conforms to:
- NSCopying
- NSCoding
Represents a notification for posting to an NSNotificationCenter . Consists of a name, an object, and an optional dictionary. The notification center will check for observers registered to receive either notifications with the name, the object, or both and pass the notification instance on to them.
This class is actually the interface for a class cluster, so instances will be of a (private) subclass.
nil
user info argument.
- Declared in:
- Foundation/NSNotification.h
- Conforms to:
- GCFinalization
GNUstep provides a framework for sending messages between objects within a process called notifications. Objects register with an NSNotificationCenter
to be informed whenever other objects post NSNotification
s to it matching certain criteria. The notification center processes notifications synchronously -- that is, control is only returned to the notification poster once every recipient of the notification has received it and processed it. Asynchronous processing is possible using an NSNotificationQueue
.
Obtain an instance using the +defaultCenter method.
In a multithreaded process, notifications are always sent on the thread that they are posted from.
Use the NSDistributedNotificationCenter for interprocess communications on the same machine.
Registers observer to receive notifications with the name notificationName and/or containing object (one or both of these two must be non-nil; nil
acts like a wildcard). When a notification of name name containing object is posted, observer receives a selector message with this notification as the argument. The notification center waits for the observer to finish processing the message, then informs the next registree matching the notification, and after all of this is done, control returns to the poster of the notification. Therefore the processing in the selector implementation should be short.
The notification center does not retain observer or object. Therefore, you should always send removeObserver: or removeObserver:name:object: to the notification center before releasing these objects.
NB. For MacOS-X compatibility, adding an observer multiple times will register it to receive multiple copies of any matching notification, however removing an observer will remove all of the multiple registrations.
nil
user info argument.
nil
, they act like wildcards. The observer may still remain registered for other notifications; use -removeObserver:
to remove it from all. If observer is nil
, the effect is to remove all registrees for the specified notifications, unless both observer and name are nil
, in which case nothing is done.
- Declared in:
- Foundation/NSNotification.h