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/*******************************************************************************
* Copyright (c) 2009, 2015 Matthew Hall 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:
* Matthew Hall - initial API and implementation (bug 263691)
* Stefan Xenos <sxenos@gmail.com> - Bug 335792
******************************************************************************/
package org.eclipse.core.databinding.observable.value;
import org.eclipse.core.databinding.observable.Diffs;
/**
* An {@link IVetoableValue} decorator for an observable value.
*
* @param <T>
* the type of value being observed
* @since 1.2
*/
public class DecoratingVetoableValue<T> extends DecoratingObservableValue<T>
implements IVetoableValue<T> {
/**
* @param decorated
* @param disposeDecoratedOnDispose
*/
public DecoratingVetoableValue(IObservableValue<T> decorated,
boolean disposeDecoratedOnDispose) {
super(decorated, disposeDecoratedOnDispose);
}
@Override
public void setValue(T value) {
checkRealm();
T currentValue = getValue();
ValueDiff<T> diff = Diffs.createValueDiff(currentValue, value);
boolean okToProceed = fireValueChanging(diff);
if (!okToProceed) {
throw new ChangeVetoException("Change not permitted"); //$NON-NLS-1$
}
super.setValue(value);
}
@Override
public synchronized void addValueChangingListener(
IValueChangingListener<T> listener) {
addListener(ValueChangingEvent.TYPE, listener);
}
@Override
public synchronized void removeValueChangingListener(
IValueChangingListener<T> listener) {
removeListener(ValueChangingEvent.TYPE, listener);
}
/**
* Notifies listeners about a pending change, and returns true if no
* listener vetoed the change.
*
* @param diff
* @return false if the change was vetoed, true otherwise
*/
protected boolean fireValueChanging(ValueDiff<T> diff) {
checkRealm();
ValueChangingEvent<T> event = new ValueChangingEvent<>(this, diff);
fireEvent(event);
return !event.veto;
}
}
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