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 org.openimaj.util.data.Context;
033import org.openimaj.util.function.Function;
034
035/**
036 * Transform a context into a stream of another type based on items extracted
037 * from the context
038 * 
039 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
040 * 
041 * @param <T>
042 *            Type of object being extracted.
043 */
044public class ContextTransform<T> implements Function<Context, T> {
045        private ContextExtractor<T> extractor;
046
047        /**
048         * Construct with the given extractor
049         * 
050         * @param extract
051         *            the extractor
052         */
053        public ContextTransform(ContextExtractor<T> extract)
054        {
055                this.extractor = extract;
056        }
057
058        /**
059         * Construct with a {@link KeyContextExtractor} using the given key.
060         * 
061         * @param key
062         *            the key to extract (a {@link KeyContextExtractor} is used)
063         */
064        public ContextTransform(String key) {
065                this.extractor = new KeyContextExtractor<T>(key);
066        }
067
068        @Override
069        public T apply(Context in) {
070                return this.extractor.extract(in);
071        }
072}