Templated class to define columns of scalars in tables. More...

#include <ScaColDesc.h>

Inheritance diagram for casa::ScalarColumnDesc< T >:

Public Member Functions
	ScalarColumnDesc (const String &name, int options=0)
	Construct the column with the given name.
	ScalarColumnDesc (const String &name, const String &comment, int options=0)
	Construct the column with the given name and comment.
	ScalarColumnDesc (const String &name, const String &comment, const String &dataManName, const String &dataManGroup, int options=0)
	Construct the column with the given name, comment, and default data manager type and group.
	ScalarColumnDesc (const String &name, const String &comment, const String &dataManName, const String &dataManGroup, const T &defaultValue, int options=0)
	Construct the column with the given name, comment, default data manager type and group, and default value.
	ScalarColumnDesc (const ScalarColumnDesc< T > &)
	Copy constructor (copy semantics);.
	~ScalarColumnDesc ()
ScalarColumnDesc< T > &	operator= (const ScalarColumnDesc< T > &)
	Assignment (copy semantics);.
BaseColumnDesc *	clone () const
	Clone this column description.
String	className () const
	Get the name of this class.
void	setDefault (const T &defaultValue)
	Set the default value.
const T &	defaultValue () const
	Get the default value.
virtual PlainColumn *	makeColumn (ColumnSet *) const
	Create a Column object out of this.
virtual ConcatColumn *	makeConcatColumn (ConcatTable *) const
	Make a ConcatColumn object out of the description.
void	show (ostream &os) const
	Show the column.
void	registerClass () const
	Register the construction function of this class.
Static Public Member Functions
static BaseColumnDesc *	makeDesc (const String &name)
	Create the object from AipsIO (this function is registered).
Private Member Functions
virtual void	putDesc (AipsIO &) const
	Put the object.
virtual void	getDesc (AipsIO &)
	Get the object.
Private Attributes
T	defaultVal_p
Friends
class	ColumnDesc

Detailed Description

template<class T>
class casa::ScalarColumnDesc< T >

Templated class to define columns of scalars in tables.

Review Status

Reviewed By:: Gareth Hunt
Date Reviewed:: 94Nov17

Intended use:

Public interface

Prerequisite

Etymology

This class builds descriptions of table columns where each cell (which may also be called a row) will hold a scalar value.

Synopsis

ScalarColumnDesc is a templated class for defining a table column containing scalar values. Note that class ScalarRecordColumnDesc has to be used to define the description of a column containing records.

The table values are handled by a data manager. This can be a storage manager to store the values in a file or it can be a virtual column engine to calculate them on-the-fly. Only the basic data types are allowed when storing in a file. These are: Bool, uChar, Short, uShort, Int, uInt, float, double, Complex, DComplex and String.

At table creation time (when a table gets created from a table description), each column needs to be bound to a data manager. If not done explicitly, the table system will bind a column to the default data manager defined in the column description.

A scalar column description consists of the following attributes:

Name, which has to be unique and must also be different from possible table keyword names.
Data type, which is determined by the template parameter (e.g. ArrayColumnDesc<Int>).
A data type id, which tells the unique name of non-standard data types (i.e. for data type == TpOther).
Comment, which defaults to an empty string. This serves purely as an informational string for the user.
Default value, which is only possible for the standard data types. It defaults to the undefined value defined in ValType.h. When a row gets added to a table, it is possible to initialize the column fields in the row with this default value.
Default data manager, which will be used if a column for a newly created table is not explicitly bound to a data manager.
Data manager group, which serves 2 purposes. Firstly it can be used in class SetupNewTable to bind a group of columns. Secondly, when the default data managers are used, it allows, for example, to have 2 StandardStMan storage managers. One for one group of columns and one for another group of columns.
Options. These are defined in ColumnDesc.h and can be combined by or-ing them. Currently only the Undefined flag applies to scalars.
Default keyword set, which defaults to an empty set. When a table column gets created from the description, it gets a copy of this keyword set as its initial keyword set.

There are several constructors, which allow to define most of the above mentioned attributes. Others, like the default keyword set, have to be defined explicitly.

This class is derived from BaseColumnDesc, thus the functions in there also apply to this class.
Once a column description is setup satisfactorily, it must be added to a table description before it can be used by the table system.

Example

        TableDesc tabDesc("tTableDesc", "1", TableDesc::New);
   
        // Add a scalar integer column ac, define keywords for it
        // and define a default value 0.
        ScalarColumnDesc<Int> acColumn("ac");
        acColumn.rwKeywordSet().define ("scale", Complex(0));
        acColumn.rwKeywordSet().define ("unit", "");
        acColumn.setDefault (0);
        tabDesc.addColumn (acColumn);
   
        // Add another column, now with data type String.\.
        // This can be added directly, because no special things like
        // keywords or default values have to be set.
        tabDesc.addColumn (ScalarColumnDesc<String>("name", "comments"));

Motivation

Several column description classes are needed to allow the user to define attributes which are special for each column type. For scalars the special attribute is the default value. They all have to be templated to support arbitrary data types.

Template Type Argument Requirements (T)

Default constructor
Copy constructor
Assignment operator
static String dataTypeId(); // (not needed for builtin types) This should return the unique "name" of the class.

Definition at line 164 of file ScaColDesc.h.

Constructor & Destructor Documentation

template<class T>

casa::ScalarColumnDesc< T >::ScalarColumnDesc	(	const String &	name,
		int	options = `0`
	)		`[explicit]`

Construct the column with the given name.

The data manager type defaults to the StandardStMan storage manager. The data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h.

template<class T>

casa::ScalarColumnDesc< T >::ScalarColumnDesc	(	const String &	name,
		const String &	comment,
		int	options = `0`
	)

Construct the column with the given name and comment.

The data manager type defaults to the StandardStMan storage manager. The data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h.

template<class T>

casa::ScalarColumnDesc< T >::ScalarColumnDesc	(	const String &	name,
		const String &	comment,
		const String &	dataManName,
		const String &	dataManGroup,
		int	options = `0`
	)

Construct the column with the given name, comment, and default data manager type and group.

A blank data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h.

template<class T>

casa::ScalarColumnDesc< T >::ScalarColumnDesc	(	const String &	name,
		const String &	comment,
		const String &	dataManName,
		const String &	dataManGroup,
		const T &	defaultValue,
		int	options = `0`
	)