/*******************************************************************************
* Copyright (c) 2007 IBM Corporation 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:
* IBM Corporation - initial API and implementation
******************************************************************************/
package org.eclipse.core.databinding;
import org.eclipse.core.databinding.conversion.IConverter;
import org.eclipse.core.databinding.observable.list.IObservableList;
import org.eclipse.core.databinding.validation.ValidationStatus;
import org.eclipse.core.internal.databinding.BindingMessages;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
/**
* Customizes a {@link Binding} between two
* {@link IObservableList observable lists}. The following behaviors can be
* customized via the strategy:
* <ul>
* <li>Conversion</li>
* <li>Automatic processing</li>
* </ul>
* <p>
* Conversion:<br/> When elements are added they can be
* {@link #convert(Object) converted} to the destination element type.
* </p>
* <p>
* Automatic processing:<br/> The processing to perform when the source
* observable changes. This behavior is configured via policies provided on
* construction of the strategy (e.g. {@link #POLICY_NEVER},
* {@link #POLICY_ON_REQUEST}, {@link #POLICY_UPDATE}).
* </p>
*
*
* @see DataBindingContext#bindList(IObservableList, IObservableList,
* UpdateListStrategy, UpdateListStrategy)
* @see IConverter
* @since 1.0
*/
public class UpdateListStrategy extends UpdateStrategy {
/**
* Policy constant denoting that the source observable's state should not be
* tracked and that the destination observable's state should never be
* updated.
*/
public static int POLICY_NEVER = notInlined(1);
/**
* Policy constant denoting that the source observable's state should not be
* tracked, but that conversion and updating the destination observable's
* state should be performed when explicitly requested.
*/
public static int POLICY_ON_REQUEST = notInlined(2);
/**
* Policy constant denoting that the source observable's state should be
* tracked, and that conversion and updating the destination observable's
* state should be performed automatically on every change of the source
* observable state.
*/
public static int POLICY_UPDATE = notInlined(8);
/**
* Helper method allowing API evolution of the above constant values. The
* compiler will not inline constant values into client code if values are
* "computed" using this helper.
*
* @param i
* an integer
* @return the same integer
*/
private static int notInlined(int i) {
return i;
}
protected IConverter converter;
private int updatePolicy;
protected boolean provideDefaults;
/**
* Creates a new update list strategy for automatically updating the
* destination observable list whenever the source observable list changes.
* A default converter will be provided. The defaults can be changed by
* calling one of the setter methods.
*/
public UpdateListStrategy() {
this(true, POLICY_UPDATE);
}
/**
* Creates a new update list strategy with a configurable update policy. A
* default converter will be provided. The defaults can be changed by
* calling one of the setter methods.
*
* @param updatePolicy
* one of {@link #POLICY_NEVER}, {@link #POLICY_ON_REQUEST}, or
* {@link #POLICY_UPDATE}
*/
public UpdateListStrategy(int updatePolicy) {
this(true, updatePolicy);
}
/**
* Creates a new update list strategy with a configurable update policy. A
* default converter will be provided if <code>provideDefaults</code> is
* <code>true</code>. The defaults can be changed by calling one of the
* setter methods.
*
* @param provideDefaults
* if <code>true</code>, default validators and a default
* converter will be provided based on the observable list's
* type.
* @param updatePolicy
* one of {@link #POLICY_NEVER}, {@link #POLICY_ON_REQUEST}, or
* {@link #POLICY_UPDATE}
*/
public UpdateListStrategy(boolean provideDefaults, int updatePolicy) {
this.provideDefaults = provideDefaults;
this.updatePolicy = updatePolicy;
}
/**
* When an element is added to the destination converts the element from the
* source element type to the destination element type.
* <p>
* Default implementation will use the
* {@link #setConverter(IConverter) converter} if one exists. If no
* converter exists no conversion occurs.
* </p>
*
* @param element
* @return the converted element
*/
public Object convert(Object element) {
return converter == null ? element : converter.convert(element);
}
/**
*
* @param source
* @param destination
*/
protected void fillDefaults(IObservableList source,
IObservableList destination) {
Object sourceType = source.getElementType();
Object destinationType = destination.getElementType();
if (provideDefaults && sourceType != null && destinationType != null) {
if (converter == null) {
setConverter(createConverter(sourceType, destinationType));
}
}
if (converter != null) {
if (sourceType != null) {
checkAssignable(converter.getFromType(), sourceType,
"converter does not convert from type " + sourceType); //$NON-NLS-1$
}
if (destinationType != null) {
checkAssignable(converter.getToType(), destinationType,
"converter does not convert to type " + destinationType); //$NON-NLS-1$
}
}
}
/**
* @return the update policy
*/
public int getUpdatePolicy() {
return updatePolicy;
}
/**
* Sets the converter to be invoked when converting added elements from the
* source element type to the destination element type.
*
* @param converter
* @return the receiver, to enable method call chaining
*/
public UpdateListStrategy setConverter(IConverter converter) {
this.converter = converter;
return this;
}
/**
* Adds the given element at the given index to the given observable list.
* Clients may extend but must call the super implementation.
*
* @param observableList
* @param element
* @param index
* @return a status
*/
protected IStatus doAdd(IObservableList observableList, Object element,
int index) {
try {
observableList.add(index, element);
} catch (Exception ex) {
return ValidationStatus.error(BindingMessages
.getString("ValueBinding_ErrorWhileSettingValue"), //$NON-NLS-1$
ex);
}
return Status.OK_STATUS;
}
/**
* Removes the element at the given index from the given observable list.
* Clients may extend but must call the super implementation.
*
* @param observableList
* @param index
* @return a status
*/
protected IStatus doRemove(IObservableList observableList, int index) {
try {
observableList.remove(index);
} catch (Exception ex) {
return ValidationStatus.error(BindingMessages
.getString("ValueBinding_ErrorWhileSettingValue"), //$NON-NLS-1$
ex);
}
return Status.OK_STATUS;
}
}