bundles/org.eclipse.core.databinding.property/src/org/eclipse/core/databinding/property/list/ListProperty.java

/*******************************************************************************
 * Copyright (c) 2008, 2010 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 194734)
 *     Matthew Hall - bug 195222
 *     Ovidio Mallo - bug 331348
 ******************************************************************************/

package org.eclipse.core.databinding.property.list;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.list.IObservableList;
import org.eclipse.core.databinding.observable.list.ListDiff;
import org.eclipse.core.databinding.observable.masterdetail.IObservableFactory;
import org.eclipse.core.databinding.observable.masterdetail.MasterDetailObservables;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.property.value.IValueProperty;
import org.eclipse.core.internal.databinding.property.ListPropertyDetailValuesList;

/**
 * Abstract implementation of IListProperty.
 * 
 * @param <S>
 *            type of the source object
 * @param <E>
 *            type of the elements in the list
 * @since 1.2
 */
public abstract class ListProperty<S, E> implements IListProperty<S, E> {

	/**
	 * By default, this method returns <code>Collections.EMPTY_LIST</code> in
	 * case the source object is <code>null</code>. Otherwise, this method
	 * delegates to {@link #doGetList(Object)}.
	 * 
	 * <p>
	 * Clients may override this method if they e.g. want to return a specific
	 * default list in case the source object is <code>null</code>.
	 * </p>
	 * 
	 * @see #doGetList(Object)
	 * 
	 * @since 1.3
	 */
	public List<E> getList(S source) {
		if (source == null) {
			return Collections.emptyList();
		}
		return Collections.unmodifiableList(doGetList(source));
	}

	/**
	 * Returns a List with the current contents of the source's list property
	 * 
	 * @param source
	 *            the property source
	 * @return a List with the current contents of the source's list property
	 * @noreference This method is not intended to be referenced by clients.
	 * @since 1.5
	 */
	protected List<E> doGetList(S source) {
		IObservableList<E> observable = observe(source);
		try {
			return new ArrayList<E>(observable);
		} finally {
			observable.dispose();
		}
	}

	/**
	 * @since 1.3
	 */
	public final void setList(S source, List<E> list) {
		if (source != null) {
			doSetList(source, list);
		}
	}

	/**
	 * Updates the property on the source with the specified change.
	 * 
	 * @param source
	 *            the property source
	 * @param list
	 *            the new list
	 * @since 1.5
	 * @noreference This method is not intended to be referenced by clients.
	 */
	protected void doSetList(S source, List<E> list) {
		doUpdateList(source, Diffs.computeListDiff(doGetList(source), list));
	}

	/**
	 * @since 1.3
	 */
	public final void updateList(S source, ListDiff<E> diff) {
		if (source != null) {
			doUpdateList(source, diff);
		}
	}

	/**
	 * Updates the property on the source with the specified change
	 * 
	 * @param source
	 *            the property source
	 * @param diff
	 *            a diff describing the change
	 * @since 1.3
	 */
	protected void doUpdateList(S source, ListDiff<E> diff) {
		IObservableList<E> observable = observe(source);
		try {
			diff.applyTo(observable);
		} finally {
			observable.dispose();
		}
	}

	public IObservableList<E> observe(S source) {
		return observe(Realm.getDefault(), source);
	}

	public IObservableFactory<S, IObservableList<E>> listFactory() {
		return new IObservableFactory<S, IObservableList<E>>() {
			public IObservableList<E> createObservable(S target) {
				return observe(target);
			}
		};
	}

	public IObservableFactory<S, IObservableList<E>> listFactory(
			final Realm realm) {
		return new IObservableFactory<S, IObservableList<E>>() {
			public IObservableList<E> createObservable(S target) {
				return observe(realm, target);
			}
		};
	}

	public <U extends S> IObservableList<E> observeDetail(
			IObservableValue<U> master) {
		return MasterDetailObservables.detailList(master,
				listFactory(master.getRealm()), getElementClass());
	}

	public final <T> IListProperty<S, T> values(
			IValueProperty<? super E, T> detailValue) {
		return new ListPropertyDetailValuesList<S, E, T>(this, detailValue);
	}

	/**
	 * This is a default implementation that should ideally be overridden to use
	 * a properly typed Class field. This implementation checks to see if the
	 * element type is of type Class and, if it is, it assumes it is the class
	 * of the elements and makes an unchecked cast.
	 * <P>
	 * This method should always be overridden to provide an implementation that
	 * never returns null.
	 * 
	 * @return the class of the elements, if possible, or null if this is not
	 *         possible
	 * @since 1.5
	 */
	public Class<E> getElementClass() {
		Object elementType = getElementType();
		if (elementType instanceof Class) {
			return (Class<E>) elementType;
		}
		return null;
	}
}