001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.operation; 023 024import cascading.flow.FlowProcess; 025import cascading.tuple.Fields; 026import cascading.tuple.Tuple; 027 028/** 029 * Class NoOp does nothing. It ignores all arguments and returns an empty {@link Tuple}, {@link Tuple#NULL}. 030 * <p> 031 * Use with {@link Fields#SWAP} to retain unknown fields, or use the {@link cascading.pipe.assembly.Discard} 032 * sub-assembly. 033 * 034 * @see Insert 035 * @see cascading.pipe.assembly.Discard 036 */ 037public class NoOp extends BaseOperation implements Function 038 { 039 /** Constructor NoOp creates a new NoOp instance that will ignore the argument values and return no output. */ 040 public NoOp() 041 { 042 super( ANY, Fields.NONE ); 043 } 044 045 @Override 046 public void operate( FlowProcess flowProcess, FunctionCall functionCall ) 047 { 048 functionCall.getOutputCollector().add( Tuple.NULL ); 049 } 050 }