001/*
002 * Copyright (c) 2015-2020, Oracle and/or its affiliates. All rights reserved.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.tribuo.data.columnar;
018
019import com.oracle.labs.mlrg.olcut.config.Configurable;
020import com.oracle.labs.mlrg.olcut.provenance.ConfiguredObjectProvenance;
021import com.oracle.labs.mlrg.olcut.provenance.Provenancable;
022
023import java.util.Optional;
024
025/**
026 * Extracts a value from a field to be placed in an {@link org.tribuo.Example}'s metadata field.
027 * Principally used to pull out Strings and floats for example names and weights respectively.
028 */
029public interface FieldExtractor<T> extends Configurable, Provenancable<ConfiguredObjectProvenance> {
030
031    /**
032     * Gets the metadata key name. This is the key into which this value will be written in an {@link org.tribuo.Example}
033     * if it is given to {@link RowProcessor}.
034     * @return The metadata key name.
035     */
036    public String getMetadataName();
037
038    /**
039     * Gets the class of the value produced by this extractor.
040     * @return The class of the value.
041     */
042    public Class<T> getValueType();
043
044    /**
045     * Returns Optional which is filled if extraction succeeded.
046     * @param row The raw row from which to extract a value
047     * @return A value.
048     */
049    Optional<T> extract(ColumnarIterator.Row row);
050}