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/*******************************************************************************
* Copyright (c) 2008 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.StateChangeEvent;
import org.eclipse.jpt.utility.model.listener.StateChangeListener;
/**
* This abstract class provides the infrastructure needed to wrap
* a model, "lazily" listen to it, and convert
* its state change notifications into property value model change
* notifications.
*
* Subclasses must override:
* - #buildValue()
* to return the current property value, as derived from the
* current model
*
* Subclasses might want to override:
* - #stateChanged(StateChangeEvent event)
* to improve performance (by not recalculating the value, if possible)
*/
public abstract class StatePropertyValueModelAdapter<T>
extends AspectPropertyValueModelAdapter<T>
{
/** The wrapped model. */
protected final Model model;
/** A listener that allows us to synch with changes to the wrapped model. */
protected final StateChangeListener stateChangeListener;
// ********** constructor/initialization **********
/**
* Construct a property value model with the specified wrapped model.
*/
protected StatePropertyValueModelAdapter(Model model) {
super();
this.model = model;
this.stateChangeListener = this.buildStateChangeListener();
}
protected StateChangeListener buildStateChangeListener() {
return new StateChangeListener() {
public void stateChanged(StateChangeEvent event) {
StatePropertyValueModelAdapter.this.stateChanged(event);
}
@Override
public String toString() {
return "state change listener";
}
};
}
// ********** behavior **********
/**
* Start listening to the model.
*/
@Override
protected void engageModel_() {
this.model.addStateChangeListener(this.stateChangeListener);
}
/**
* Stop listening to the model.
*/
@Override
protected void disengageModel_() {
this.model.removeStateChangeListener(this.stateChangeListener);
}
@Override
public void toString(StringBuilder sb) {
sb.append(this.model);
}
// ********** state change support **********
/**
* The model's state changed;
* propagate the change notification appropriately.
*/
protected void stateChanged(StateChangeEvent event) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
}
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