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/*******************************************************************************
* Copyright (c) 2009 Oracle. 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:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal.model.value;
import org.eclipse.jpt.utility.model.Model;
import org.eclipse.jpt.utility.model.event.ChangeEvent;
import org.eclipse.jpt.utility.model.listener.ChangeListener;
import org.eclipse.jpt.utility.model.listener.CommandChangeListener;
/**
* This abstract class provides the infrastructure needed to wrap
* a model, "lazily" listen to it, and convert
* its change notifications into property value model change
* notifications.
* <p>
* Subclasses must override:<ul>
* <li>{@link #buildValue()}<p>
* to return the current property value, as derived from the
* current model
* </ul>
* Subclasses might want to override the following methods
* to improve performance (by not recalculating the value, if possible):<ul>
* <li>{@link #modelChanged(ChangeEvent event)}
* <li>{@link #buildChangeListener()}
* </ul>
*/
public abstract class ChangePropertyValueModelAdapter<T>
extends AbstractPropertyValueModelAdapter<T>
{
/** The wrapped model. */
protected final Model model;
/** A listener that allows us to synch with changes to the wrapped collection holder. */
protected final ChangeListener changeListener;
// ********** constructor/initialization **********
/**
* Construct a property value model with the specified wrapped model.
*/
protected ChangePropertyValueModelAdapter(Model model) {
super();
this.model = model;
this.changeListener = this.buildChangeListener();
}
protected ChangeListener buildChangeListener() {
return new CommandChangeListener() {
@Override
protected void modelChanged(ChangeEvent event) {
ChangePropertyValueModelAdapter.this.modelChanged(event);
}
@Override
public String toString() {
return "change listener command"; //$NON-NLS-1$
}
};
}
// ********** behavior **********
/**
* Start listening to the model.
*/
@Override
protected void engageModel_() {
this.model.addChangeListener(this.changeListener);
}
/**
* Stop listening to the model.
*/
@Override
protected void disengageModel_() {
this.model.removeChangeListener(this.changeListener);
}
// ********** change support **********
/**
* The wrapped model has changed;
* propagate the change notification appropriately.
*/
protected void modelChanged(@SuppressWarnings("unused") ChangeEvent event) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
}
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