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/*******************************************************************************
* Copyright (c) 2007, 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.internal.Transformer;
import org.eclipse.jpt.utility.model.event.PropertyChangeEvent;
import org.eclipse.jpt.utility.model.value.PropertyValueModel;
/**
* A <code>TransformationPropertyValueModel</code> wraps another
* <code>PropertyValueModel</code> and uses a <code>Transformer</code>
* to transform the wrapped value before it is returned by <code>value()</code>.
* <p>
* As an alternative to building a <code>Transformer</code>,
* a subclass of <code>TransformationPropertyValueModel</code> can
* either override the <code>transform_(Object)</code> method or,
* if something other than null should be returned when the wrapped value
* is null, override the <code>transform(Object)</code> method.
*/
public class TransformationPropertyValueModel<T1, T2>
extends PropertyValueModelWrapper<T1>
implements PropertyValueModel<T2>
{
protected final Transformer<T1, T2> transformer;
// ********** constructors/initialization **********
/**
* Construct a property value model with the specified nested
* property value model and the default transformer.
* Use this constructor if you want to override the
* <code>transform_(Object)</code> or <code>transform(Object)</code>
* method instead of building a <code>Transformer</code>.
*/
public TransformationPropertyValueModel(PropertyValueModel<? extends T1> valueHolder) {
super(valueHolder);
this.transformer = this.buildTransformer();
}
/**
* Construct an property value model with the specified nested
* property value model and transformer.
*/
public TransformationPropertyValueModel(PropertyValueModel<? extends T1> valueHolder, Transformer<T1, T2> transformer) {
super(valueHolder);
this.transformer = transformer;
}
protected Transformer<T1, T2> buildTransformer() {
return new DefaultTransformer();
}
// ********** PropertyValueModel implementation **********
public T2 getValue() {
// transform the object returned by the nested value model before returning it
return this.transform(this.valueHolder.getValue());
}
// ********** PropertyValueModelWrapper implementation **********
@Override
protected void valueChanged(PropertyChangeEvent event) {
// transform the values before propagating the change event
@SuppressWarnings("unchecked")
Object oldValue = this.transform((T1) event.getOldValue());
@SuppressWarnings("unchecked")
Object newValue = this.transform((T1) event.getNewValue());
this.firePropertyChanged(VALUE, oldValue, newValue);
}
// ********** behavior **********
/**
* Transform the specified value and return the result.
* This is called by #value() and #valueChanged(PropertyChangeEvent).
*/
protected T2 transform(T1 value) {
return this.transformer.transform(value);
}
/**
* Transform the specified, non-null, value and return the result.
*/
protected T2 transform_(T1 value) {
throw new UnsupportedOperationException();
}
// ********** default transformer **********
/**
* The default transformer will return null if the wrapped value is null.
* If the wrapped value is not null, it is transformed by a subclass
* implementation of #transform_(Object).
*/
protected class DefaultTransformer implements Transformer<T1, T2> {
public T2 transform(T1 value) {
return (value == null) ? null : TransformationPropertyValueModel.this.transform_(value);
}
}
}
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