nsIObserverService
 
 Service allows a client listener (nsIObserver) to register and unregister for 
 notifications of specific string referenced topic. Service also provides a 
 way to notify registered listeners and a way to enumerate registered client 
 listeners.
 
 @status FROZEN
[scriptable, uuid(d07f5192-e3d1-11d2-8acd-00105a1b8860)]
interface nsIObserverService : nsISupports

Methods

 AddObserver

 Registers a given listener for a notifications regarding the specified
 topic.

 @param anObserve : The interface pointer which will receive notifications.
 @param aTopic    : The notification topic or subject.
 @param ownsWeak  : If set to false, the nsIObserverService will hold a 
                    strong reference to |anObserver|.  If set to true and 
                    |anObserver| supports the nsIWeakReference interface,
                    a weak reference will be held.  Otherwise an error will be
                    returned.
void addObserver(in nsIObserver anObserver, in string aTopic, in boolean ownsWeak) 
 enumerateObservers

 Returns an enumeration of all registered listeners.

 @param aTopic   : The notification topic or subject.
nsISimpleEnumerator enumerateObservers(in string aTopic) 
 notifyObservers

 Notifies all registered listeners of the given topic.

 @param aSubject : Notification specific interface pointer.
 @param aTopic   : The notification topic or subject.
 @param someData : Notification specific wide string.
void notifyObservers(in nsISupports aSubject, in string aTopic, in wstring someData) 
 removeObserver

 Unregisters a given listener from notifications regarding the specified
 topic.

 @param anObserver : The interface pointer which will stop recieving
                     notifications.
 @param aTopic     : The notification topic or subject.
void removeObserver(in nsIObserver anObserver, in string aTopic)