    001/*
    002 * Copyright (c) 2007-2016 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
    021package cascading.operation;
    022
    023import cascading.flow.FlowProcess;
    024import cascading.tuple.Fields;
    025import 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 */
    036public 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  }