    001    /*
    002     * Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
    003     *
    004     * Project and contact information: http://www.cascading.org/
    005     *
    006     * This file is part of the Cascading project.
    007     *
    008     * Licensed under the Apache License, Version 2.0 (the "License");
    009     * you may not use this file except in compliance with the License.
    010     * You may obtain a copy of the License at
    011     *
    012     *     http://www.apache.org/licenses/LICENSE-2.0
    013     *
    014     * Unless required by applicable law or agreed to in writing, software
    015     * distributed under the License is distributed on an "AS IS" BASIS,
    016     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017     * See the License for the specific language governing permissions and
    018     * limitations under the License.
    019     */
    020
    021    package cascading.operation;
    022
    023    import cascading.flow.FlowProcess;
    024    import cascading.tuple.Fields;
    025    import cascading.tuple.Tuple;
    026
    027    /**
    028     * Class NoOp does nothing. It ignores all arguments and returns an empty {@link Tuple}, {@link Tuple#NULL}.
    029     * <p/>
    030     * Use with {@link Fields#SWAP} to retain unknown fields, or use the {@link cascading.pipe.assembly.Discard}
    031     * sub-assembly.
    032     *
    033     * @see Insert
    034     * @see cascading.pipe.assembly.Discard
    035     */
    036    public class NoOp extends BaseOperation implements Function
    037      {
    038      /** Constructor NoOp creates a new NoOp instance that will ignore the argument values and return no output. */
    039      public NoOp()
    040        {
    041        super( ANY, Fields.NONE );
    042        }
    043
    044      @Override
    045      public void operate( FlowProcess flowProcess, FunctionCall functionCall )
    046        {
    047        functionCall.getOutputCollector().add( Tuple.NULL );
    048        }
    049      }