ScaColDesc.h

Classes

ScalarColumnDesc -- Templated class to define columns of scalars in tables (full description)

class ScalarColumnDesc : public BaseColumnDesc

Interface

Public Members

explicit ScalarColumnDesc (const String& name, int options = 0)

ScalarColumnDesc (const String& name, const String& comment, int options = 0)

ScalarColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, int options = 0)

ScalarColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, const T& defaultValue, int options = 0)

ScalarColumnDesc (const ScalarColumnDesc<T>&)

~ScalarColumnDesc()

ScalarColumnDesc<T>& operator= (const ScalarColumnDesc<T>&)

BaseColumnDesc* clone() const

String className() const

void setDefault (const T& defaultValue)

const T& defaultValue() const

PlainColumn* makeColumn (ColumnSet*) const

void show (ostream& os) const

Private Members

static BaseColumnDesc* makeDesc (const String& name)

virtual void putDesc (AipsIO&) const

virtual void getDesc (AipsIO&)

Public Members

ScalarColumnDesc (SimpleOrderedMap<String, BaseColumnDesc* (*)(const String&)>&)

Description

Review Status

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

Prerequisite

BaseColumnDesc
TableDesc

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).
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.

To Do

Member Description

explicit ScalarColumnDesc (const String& name, int options = 0)

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.

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.

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.

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

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. It is used by the registration process. The template argument gets part of the name.

void setDefault (const T& defaultValue)

Set the default value.

const T& defaultValue() const

Get the default value.

PlainColumn* makeColumn (ColumnSet*) const

Create a Column object out of this. This is used by class ColumnSet to construct a table column object.

void show (ostream& os) const

Show the column.

static BaseColumnDesc* makeDesc (const String& name)

Create the object from AipsIO (this function is registered).

virtual void putDesc (AipsIO&) const

Put the object.

virtual void getDesc (AipsIO&)

Get the object.

ScalarColumnDesc (SimpleOrderedMap<String, BaseColumnDesc* (*)(const String&)>&)

The purpose of this constructor is to register the makeDesc function of this class and map it to a name. ColumnDesc.cc registers such functions by using these constructors.