TableMeasValueDesc.h

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00001 //# TableMeasValueDesc.h: Definition of a MeasValue in a Table.
00002 //# Copyright (C) 1997,1999,2000,2001
00003 //# Associated Universities, Inc. Washington DC, USA.
00004 //#
00005 //# This library is free software; you can redistribute it and/or modify it
00006 //# under the terms of the GNU Library General Public License as published by
00007 //# the Free Software Foundation; either version 2 of the License, or (at your
00008 //# option) any later version.
00009 //#
00010 //# This library is distributed in the hope that it will be useful, but WITHOUT
00011 //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
00012 //# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
00013 //# License for more details.
00014 //#
00015 //# You should have received a copy of the GNU Library General Public License
00016 //# along with this library; if not, write to the Free Software Foundation,
00017 //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
00018 //#
00019 //# Correspondence concerning AIPS++ should be addressed as follows:
00020 //#        Internet email: aips2-request@nrao.edu.
00021 //#        Postal address: AIPS++ Project Office
00022 //#                        National Radio Astronomy Observatory
00023 //#                        520 Edgemont Road
00024 //#                        Charlottesville, VA 22903-2475 USA
00025 //#
00026 //# $Id$
00027 
00028 #ifndef MEASURES_TABLEMEASVALUEDESC_H
00029 #define MEASURES_TABLEMEASVALUEDESC_H
00030 
00031 //# Includes
00032 #include <casacore/casa/aips.h>
00033 #include <casacore/casa/BasicSL/String.h>
00034 
00035 namespace casacore { //# NAMESPACE CASACORE - BEGIN
00036 
00037 //# Forward Declarations
00038 class ColumnDesc;
00039 class Table;
00040 class TableDesc;
00041 class TableRecord;
00042 
00043 
00044 // <summary>
00045 // Definition of a Measure Value in a Table.
00046 // </summary>
00047 
00048 // <use visibility=export>
00049 
00050 // <reviewed reviewer="Bob Garwood" date="1999/12/23" tests="tTableMeasures.cc">
00051 // </reviewed>
00052 
00053 // <prerequisite>
00054 //# Classes you should understand before using this one.
00055 //   <li> <linkto module=Measures>Measures</linkto>
00056 //   <li> <linkto module=Tables>Tables</linkto>
00057 //   <li> <linkto class=TableMeasDesc>TableMeasDesc</linkto>
00058 // </prerequisite>
00059 
00060 // <synopsis>
00061 // TableMeasValueDesc is a class for setting up the Measure value
00062 // component of the TableMeasDesc in the TableMeasures system.   Its purpose
00063 // it to specify the Table column to be used as a Measure column through
00064 // which Measures are subsequently written to and read from via
00065 // either an <linkto class="ArrayMeasColumn">ArrayMeasColumn</linkto>
00066 // or <linkto class="ScalarMeasColumn">ScalarMeasColumn</linkto> object.
00067 //
00068 // The column used as the Measure column is always an ArrayColumn<Double>
00069 // irrespective of whether it is to store scalars or arrays of Measures and
00070 // irrespective of the type of Measure.
00071 // </synopsis>
00072 
00073 // <example>
00074 //<ol>
00075 // <li>
00076 // <srcblock>
00077 //    // Add a column to the table.  This column is to be used to store
00078 //    // MPositions.  Measure columns are alway ArrayColumn<Double>
00079 //    ArrayColumnDesc<Double> cdPosCol("MPosColumn", "MPosition column");
00080 //    td.addColumn(cdPosCol);
00081 //    ...
00082 //    // create the TableMeasValueDesc object
00083 //    TableMeasValueDesc valueDesc(td, "MPosColumn");
00084 // </srcblock>
00085 //</ol>
00086 // For an example of the use of the TableMeasValueDesc class in the context
00087 // of a full TableMeasDesc declaration see class
00088 // <linkto class="TableMeasDesc">TableMeasDesc</linkto>.
00089 // </example>
00090 
00091 // <motivation>
00092 // Creating the required keyword for the definition of a Measure
00093 // in a Table is somewhat complicated. This class assists in that
00094 // process.
00095 // </motivation>
00096 //
00097 // <thrown>
00098 //    <li>AipsError if the specified column doesn't exist or it isn't
00099 //      an ArrayColumn or its type is not Double.
00100 // </thrown>
00101 //
00102 //# <todo asof="$DATE:$">
00103 //# A List of bugs, limitations, extensions or planned refinements.
00104 //# </todo>
00105 
00106 
00107 class TableMeasValueDesc
00108 {
00109 public:
00110   // Null constructor
00111   TableMeasValueDesc();
00112 
00113   // Construct the MeasValue column descriptor for the given column.
00114   // The column must be a column of type Double and should exist in
00115   // the TableDesc.
00116   TableMeasValueDesc (const TableDesc&, const String& columnName);
00117 
00118   // Construct the MeasValue column descriptor for the given column.
00119   // Checking if the column exists is done in the write function.
00120   // <group>
00121   TableMeasValueDesc (const String& columnName)
00122     : itsColumn (columnName) {}
00123   TableMeasValueDesc (const Char* columnName)
00124     : itsColumn (columnName) {}
00125   // </group>
00126 
00127   // Copy constructor.
00128   TableMeasValueDesc (const TableMeasValueDesc& that);
00129 
00130   ~TableMeasValueDesc();
00131 
00132   // Assignment operator.
00133   TableMeasValueDesc& operator= (const TableMeasValueDesc& that);
00134 
00135   // Write the type, unit, and MEASINFO record into the column keywords.
00136   // It checks if the column exists in the given table description.
00137   // <group>
00138   void write (TableDesc&, const TableRecord& measInfo);
00139   void write (Table&, const TableRecord& measInfo);
00140   // </group>
00141 
00142   // Get the name of the underlying column.
00143   const String& columnName() const
00144     { return itsColumn; }
00145 
00146 private:
00147   String itsColumn;         //# MeasValue column name.
00148 
00149 
00150   // Write the actual keywords.
00151   void writeKeys (TableRecord& columnKeyset,
00152                   const TableRecord& measInfo);
00153 
00154   // Throw an exception if the quantum column doesn't exist or is of the
00155   // wrong type.
00156   void checkColumn (const TableDesc& td) const;
00157 };
00158 
00159 
00160 
00161 } //# NAMESPACE CASACORE - END
00162 
00163 #endif
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