bundles/org.eclipse.core.databinding.property/src/org/eclipse/core/databinding/property/value/SimpleValueProperty.java

/*******************************************************************************
 * Copyright (c) 2008 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 - bugs 195222, 247997, 265561
 ******************************************************************************/

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

import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.list.IObservableList;
import org.eclipse.core.databinding.observable.map.IObservableMap;
import org.eclipse.core.databinding.observable.set.IObservableSet;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.property.INativePropertyListener;
import org.eclipse.core.databinding.property.ISimplePropertyListener;
import org.eclipse.core.internal.databinding.property.value.ListSimpleValueObservableList;
import org.eclipse.core.internal.databinding.property.value.MapSimpleValueObservableMap;
import org.eclipse.core.internal.databinding.property.value.SetSimpleValueObservableMap;
import org.eclipse.core.internal.databinding.property.value.SimplePropertyObservableValue;

/**
 * Simplified abstract implementation of IValueProperty. This class takes care
 * of most of the functional requirements for an IValueProperty implementation,
 * leaving only the property-specific details to subclasses.
 * <p>
 * Subclasses must implement these methods:
 * <ul>
 * <li> {@link #getValueType()}
 * <li> {@link #doGetValue(Object)}
 * <li> {@link #doSetValue(Object, Object)}
 * <li> {@link #adaptListener(ISimplePropertyListener)}
 * </ul>
 * <p>
 * In addition, we recommended overriding {@link #toString()} to return a
 * description suitable for debugging purposes.
 * 
 * @since 1.2
 */
public abstract class SimpleValueProperty extends ValueProperty {
	/**
	 * Returns the value of the property on the specified source object
	 * 
	 * @param source
	 *            the property source (may be null)
	 * @return the current value of the source's value property
	 * @noreference This method is not intended to be referenced by clients.
	 */
	public final Object getValue(Object source) {
		return source == null ? null : doGetValue(source);
	}

	/**
	 * Returns the value of the property on the specified source object
	 * 
	 * @param source
	 *            the property source
	 * @return the current value of the source's value property
	 * @noreference This method is not intended to be referenced by clients.
	 */
	protected abstract Object doGetValue(Object source);

	/**
	 * Sets the source's value property to the specified value
	 * 
	 * @param source
	 *            the property source
	 * @param value
	 *            the new value
	 * @noreference This method is not intended to be referenced by clients.
	 */
	public final void setValue(Object source, Object value) {
		if (source != null)
			doSetValue(source, value);
	}

	protected abstract void doSetValue(Object source, Object value);

	/**
	 * Returns a listener capable of adding or removing itself as a listener on
	 * a source object using the the source's "native" listener API. Events
	 * received from the source objects are parlayed to the specified listener
	 * argument.
	 * <p>
	 * This method returns null if the source object has no listener APIs for
	 * this property.
	 * 
	 * @param listener
	 *            the property listener to receive events
	 * @return a native listener which parlays property change events to the
	 *         specified listener, or null if the source object has no listener
	 *         APIs for this property.
	 * @noreference This method is not intended to be referenced by clients.
	 */
	public abstract INativePropertyListener adaptListener(
			ISimplePropertyListener listener);

	public IObservableValue observe(Realm realm, Object source) {
		return new SimplePropertyObservableValue(realm, source, this);
	}

	public IObservableList observeDetail(IObservableList master) {
		return new ListSimpleValueObservableList(master, this);
	}

	public IObservableMap observeDetail(IObservableSet master) {
		return new SetSimpleValueObservableMap(master, this);
	}

	public IObservableMap observeDetail(IObservableMap master) {
		return new MapSimpleValueObservableMap(master, this);
	}
}