TableMeasValueDesc.h

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// # TableMeasValueDesc.h: Definition of a MeasValue in a Table.
// # Copyright (C) 1997,1999,2000,2001
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef MEASURES_TABLEMEASVALUEDESC_H
#define MEASURES_TABLEMEASVALUEDESC_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/BasicSL/String.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class ColumnDesc;
class Table;
class TableDesc;
class TableRecord;
 
// <summary>
// Definition of a Measure Value in a Table.
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="Bob Garwood" date="1999/12/23" tests="tTableMeasures.cc">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> <linkto module=Measures>Measures</linkto>
//   <li> <linkto module=Tables>Tables</linkto>
//   <li> <linkto class=TableMeasDesc>TableMeasDesc</linkto>
// </prerequisite>
 
// <synopsis>
// TableMeasValueDesc is a class for setting up the Measure value
// component of the TableMeasDesc in the TableMeasures system.   Its purpose
// it to specify the Table column to be used as a Measure column through
// which Measures are subsequently written to and read from via
// either an <linkto class="ArrayMeasColumn">ArrayMeasColumn</linkto>
// or <linkto class="ScalarMeasColumn">ScalarMeasColumn</linkto> object.
//
// The column used as the Measure column is always an ArrayColumn<Double>
// irrespective of whether it is to store scalars or arrays of Measures and
// irrespective of the type of Measure.
// </synopsis>
 
// <example>
//<ol>
// <li>
// <srcblock>
//    // Add a column to the table.  This column is to be used to store
//    // MPositions.  Measure columns are alway ArrayColumn<Double>
//    ArrayColumnDesc<Double> cdPosCol("MPosColumn", "MPosition column");
//    td.addColumn(cdPosCol);
//    ...
//    // create the TableMeasValueDesc object
//    TableMeasValueDesc valueDesc(td, "MPosColumn");
// </srcblock>
//</ol>
// For an example of the use of the TableMeasValueDesc class in the context
// of a full TableMeasDesc declaration see class
// <linkto class="TableMeasDesc">TableMeasDesc</linkto>.
// </example>
 
// <motivation>
// Creating the required keyword for the definition of a Measure
// in a Table is somewhat complicated. This class assists in that
// process.
// </motivation>
//
// <thrown>
//    <li>AipsError if the specified column doesn't exist or it isn't
//  an ArrayColumn or its type is not Double.
// </thrown>
//
// # <todo asof="$DATE:$">
// # A List of bugs, limitations, extensions or planned refinements.
// # </todo>
 
class TableMeasValueDesc {
 public:
  // Null constructor
  TableMeasValueDesc();
 
  // Construct the MeasValue column descriptor for the given column.
  // The column must be a column of type Double and should exist in
  // the TableDesc.
  TableMeasValueDesc(const TableDesc&, const String& columnName);
 
  // Construct the MeasValue column descriptor for the given column.
  // Checking if the column exists is done in the write function.
  // <group>
  TableMeasValueDesc(const String& columnName) : itsColumn(columnName) {}
  TableMeasValueDesc(const Char* columnName) : itsColumn(columnName) {}
  // </group>
 
  // Copy constructor.
  TableMeasValueDesc(const TableMeasValueDesc& that);
 
  ~TableMeasValueDesc();
 
  // Assignment operator.
  TableMeasValueDesc& operator=(const TableMeasValueDesc& that);
 
  // Write the type, unit, and MEASINFO record into the column keywords.
  // It checks if the column exists in the given table description.
  // <group>
  void write(TableDesc&, const TableRecord& measInfo);
  void write(Table&, const TableRecord& measInfo);
  // </group>
 
  // Get the name of the underlying column.
  const String& columnName() const { return itsColumn; }
 
 private:
  String itsColumn;  // # MeasValue column name.
 
  // Write the actual keywords.
  void writeKeys(TableRecord& columnKeyset, const TableRecord& measInfo);
 
  // Throw an exception if the quantum column doesn't exist or is of the
  // wrong type.
  void checkColumn(const TableDesc& td) const;
};
 
}  // namespace casacore
 
#endif