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/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Intersect Software Corporation
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/
package net.wotonomy.control;
import java.util.Observable;
import java.util.Observer;
/**
* This is an abstract class for receiving coalesced notifications of changes
* from objects. This class also implements Observer for greater compatibility.
* The point of EODelayedObservers is that when they receive a willChange
* message, they queue themselves with a EODelayedObserverQueue so they can
* receive a single subjectChanged() after all changes from an observed object
* take place.
*
* @author michael@mpowers.net
* @author $Author: cgruber $
* @version $Revision: 894 $
*/
public abstract class EODelayedObserver implements EOObserving, Observer {
/**
* Notified immediately.
*/
public static final int ObserverPriorityImmediate = 0;
public static final int ObserverPriorityFirst = 1;
public static final int ObserverPrioritySecond = 2;
public static final int ObserverPriorityThird = 3;
public static final int ObserverPriorityFourth = 4;
public static final int ObserverPriorityFifth = 5;
public static final int ObserverPrioritySixth = 6;
public static final int ObserverPriorityLater = 7;
public static final int ObserverNumberOfPriorities = 8;
/**
* Default constructor.
*/
public EODelayedObserver() {
}
/**
* Removes this observer from the observer queue for a currently pending
* notification.
*/
public void discardPendingNotification() {
observerQueue().dequeueObserver(this);
}
/**
* Returns the observer queue to which this observer belongs. This
* implementation returns the default EODelayedObserverQueue. Override to use a
* different one.
*/
public EODelayedObserverQueue observerQueue() {
return EODelayedObserverQueue.defaultObserverQueue();
}
/**
* Returns the priority of this observer in the queue. This implementation
* returns ObserverPriorityThird. Override to be notified before other
* observers.
*/
public int priority() {
return ObserverPriorityThird;
}
/**
* Notifies observer that one or more objects that it is observing have changed.
* The observer should check all objects it is observing for changes.
*/
public abstract void subjectChanged();
// interface EOObserving
/**
* Called when the specified object is about to change. This implementation puts
* this observer on a notification queue.
*/
public void objectWillChange(Object anObject) {
observerQueue().enqueueObserver(this);
}
// interface Observer
/**
* Called when the specified object has changed, with the specified argument.
* This method is included for interacting with the java.lang.Observer pattern.
* This implementation simply objectWillChange(anObject) so that the observer
* still gets a single subjectChanged call in response to multiple changes.
*/
public void update(Observable anObject, Object aValue) {
objectWillChange(anObject);
}
}
/*
* $Log$ Revision 1.2 2006/02/16 16:47:14 cgruber Move some classes in to
* "internal" packages and re-work imports, etc.
*
* Also use UnsupportedOperationExceptions where appropriate, instead of
* WotonomyExceptions.
*
* Revision 1.1 2006/02/16 13:19:57 cgruber Check in all sources in
* eclipse-friendly maven-enabled packages.
*
* Revision 1.2 2001/10/26 18:38:10 mpowers Reordered priorities.
*
* Revision 1.1.1.1 2000/12/21 15:46:38 mpowers Contributing wotonomy.
*
* Revision 1.3 2000/12/20 16:25:35 michael Added log to all files.
*
*
*/
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