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/*
* Copyright 2009 Andrew Pietsch
*
* Licensed under the Apache License, Version 2.0 (the "License"); you
* may not use this file except in compliance with the License. You may
* obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing permissions
* and limitations under the License.
*/
package com.dragome.forms.bindings.client.value;
import com.dragome.forms.bindings.client.function.Function;
import com.dragome.model.interfaces.ValueChangeEvent;
import com.dragome.model.interfaces.ValueChangeHandler;
/**
* Created by IntelliJ IDEA.
* User: andrew
* Date: Oct 28, 2009
* Time: 11:14:29 AM
* To change this template use File | Settings | File Templates.
*/
public class ComputedValueModel extends AbstractValueModel
{
private ValueChangeHandler changeMonitor= new ValueChangeHandler()
{
public void onValueChange(ValueChangeEvent event)
{
recompute();
}
};
private ValueModel source;
private Function function;
private T cachedValue;
public ComputedValueModel(ValueModel source, Function function)
{
if (source == null)
{
throw new NullPointerException("source is null");
}
if (function == null)
{
throw new NullPointerException("function is null");
}
this.source= source;
this.function= function;
this.source.addValueChangeHandler(changeMonitor);
recompute();
}
protected void recompute()
{
T oldValue= cachedValue;
cachedValue= function.compute(source.getValue());
fireValueChangeEvent(oldValue, cachedValue);
}
public T getValue()
{
return cachedValue;
}
public Function getFunction()
{
return function;
}
public void setFunction(Function function)
{
if (function == null)
{
throw new NullPointerException("function is null");
}
this.function= function;
recompute();
}
}