NullRemovingSelectorModel.java

/**
 * Copyright (c) 2004-2025 Carnegie Mellon University and others. (see Contributors file).
 * All Rights Reserved.
 *
 * NO WARRANTY. ALL MATERIAL IS FURNISHED ON AN "AS-IS" BASIS. CARNEGIE MELLON UNIVERSITY MAKES NO WARRANTIES OF ANY
 * KIND, EITHER EXPRESSED OR IMPLIED, AS TO ANY MATTER INCLUDING, BUT NOT LIMITED TO, WARRANTY OF FITNESS FOR PURPOSE
 * OR MERCHANTABILITY, EXCLUSIVITY, OR RESULTS OBTAINED FROM USE OF THE MATERIAL. CARNEGIE MELLON UNIVERSITY DOES NOT
 * MAKE ANY WARRANTY OF ANY KIND WITH RESPECT TO FREEDOM FROM PATENT, TRADEMARK, OR COPYRIGHT INFRINGEMENT.
 *
 * This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 * SPDX-License-Identifier: EPL-2.0
 *
 * Created, in part, with funding and support from the United States Government. (see Acknowledgments file).
 *
 * This program includes and/or can make use of certain third party source code, object code, documentation and other
 * files ("Third Party Software"). The Third Party Software that is used by this program is dependent upon your system
 * configuration. By using this program, You agree to comply with any and all relevant Third Party Software terms and
 * conditions contained in any such Third Party Software or separate license file distributed with such Third Party
 * Software. The parties who own the Third Party Software ("Third Party Licensors") are intended third party benefici-
 * aries to this license with respect to the terms applicable to their Third Party Software. Third Party Software li-
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 */
package org.osate.ge.swt.selectors;

import java.util.stream.Stream;

/**
 * {@link SelectorModel} implementation that replaces null elements with an object representing null.
 * This class is intended to be used as an implementation detail when implementing selectors using JFace components which do not support null.
 *
 */
class NullRemovingSelectorModel extends SelectorModelDecorator<Object> {
	private static final Object nullObject = new Object();

	/**
	 * Creates a new instance
	 * @param inner the selector model to wrap.
	 */
	@SuppressWarnings("unchecked")
	public NullRemovingSelectorModel(final SelectorModel<?> inner) {
		super((SelectorModel<Object>) inner);
	}

	@Override
	public Stream<Object> getElements() {
		return super.getElements().map(NullRemovingSelectorModel::nullToObject);
	}

	@Override
	public Stream<Object> getSelectedElements() {
		return super.getSelectedElements().map(NullRemovingSelectorModel::nullToObject);
	}

	@Override
	public void setSelectedElements(final Stream<Object> value) {
		super.setSelectedElements(
				value.map(NullRemovingSelectorModel::objectToNull));
	}

	@Override
	public String getLabel(final Object element) {
		return super.getLabel(objectToNull(element));
	}

	private static Object nullToObject(Object value) {
		return value == null ? nullObject : value;
	}

	private static Object objectToNull(Object value) {
		return value == nullObject ? null : value;
	}
}