bundles/org.eclipse.core.databinding/src/org/eclipse/core/internal/databinding/observable/ProxyObservableSet.java

/*******************************************************************************
 * Copyright (c) 2006, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Matthew Hall - bug 208332
 *******************************************************************************/

package org.eclipse.core.internal.databinding.observable;

import java.util.Collections;
import java.util.Set;

import org.eclipse.core.databinding.observable.IStaleListener;
import org.eclipse.core.databinding.observable.StaleEvent;
import org.eclipse.core.databinding.observable.set.AbstractObservableSet;
import org.eclipse.core.databinding.observable.set.IObservableSet;
import org.eclipse.core.databinding.observable.set.ISetChangeListener;
import org.eclipse.core.databinding.observable.set.SetChangeEvent;

/**
 * Wraps an observable set. This object acts like an exact copy of the original
 * set, and tracks all the changes in the original. The only difference is that
 * disposing the wrapper will not dispose the original. You can use this
 * whenever you need to return an IObservableSet from a method that expects the
 * caller to dispose the set, but you have an IObservableSet that you don't want
 * disposed.
 */
public class ProxyObservableSet extends AbstractObservableSet {
	private IObservableSet wrappedSet;
	private Object elementType;

	private ISetChangeListener setChangeListener = new ISetChangeListener() {
		public void handleSetChange(SetChangeEvent event) {
			fireSetChange(event.diff);
		}
	};

	private IStaleListener staleListener = new IStaleListener() {
		public void handleStale(StaleEvent staleEvent) {
			fireStale();
		}
	};

	/**
	 * Constructs a ProxyObservableSet that tracks the state of the given set.
	 * 
	 * @param wrappedSet
	 *            the set being wrapped
	 */
	public ProxyObservableSet(IObservableSet wrappedSet) {
		super(wrappedSet.getRealm());
		this.wrappedSet = wrappedSet;
		this.elementType = wrappedSet.getElementType();
		wrappedSet.addSetChangeListener(setChangeListener);
		wrappedSet.addStaleListener(staleListener);
	}

	protected Set getWrappedSet() {
		return wrappedSet == null ? Collections.EMPTY_SET : wrappedSet;
	}

	public Object getElementType() {
		return elementType;
	}

	public boolean isStale() {
		getterCalled();
		return wrappedSet == null ? false : wrappedSet.isStale();
	}

	public void dispose() {
		if (wrappedSet != null) {
			wrappedSet.removeSetChangeListener(setChangeListener);
			setChangeListener = null;
			wrappedSet.removeStaleListener(staleListener);
			staleListener = null;
			wrappedSet = null;
		}
		elementType = null;
		super.dispose();
	}
}