001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.util.function.context;
031
032import java.util.ArrayList;
033import java.util.List;
034
035import org.openimaj.util.data.Context;
036import org.openimaj.util.function.Function;
037
038/**
039 * Transform a {@link List} of {@link Context} instances to a stream of
040 * {@link List} of T. The extraction strategy is used on each item in the list.
041 * 
042 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
043 * 
044 * @param <T>
045 *            Type of elements in the {@link Context} being extracted
046 */
047public class ContextListTransform<T> implements Function<List<Context>, List<T>> {
048        private ContextExtractor<T> extractor;
049
050        /**
051         * Construct with the given extractor.
052         * 
053         * @param extract
054         *            the extractor
055         */
056        public ContextListTransform(ContextExtractor<T> extract)
057        {
058                this.extractor = extract;
059        }
060
061        /**
062         * Construct using a {@link KeyContextExtractor} with the given key.
063         * 
064         * @param key
065         *            the key to extract
066         */
067        public ContextListTransform(String key) {
068                this.extractor = new KeyContextExtractor<T>(key);
069        }
070
071        @Override
072        public List<T> apply(List<Context> in) {
073                final List<T> ret = new ArrayList<T>();
074                for (final Context context : in) {
075                        ret.add(this.extractor.extract(context));
076                }
077                return ret;
078        }
079}