Access to an individual field in a record. More...

#include <RecordField.h>

Inheritance diagram for casacore::RecordFieldPtr< T >:

Public Member Functions
	RecordFieldPtr ()
	This object does not point to any field, i.e. More...

	RecordFieldPtr (RecordInterface &record, Int whichField)
	Attach this field pointer to the given field. More...

	RecordFieldPtr (RecordInterface &record, const RecordFieldId &)

	RecordFieldPtr (const RecordFieldPtr< T > &other)
	After calling, this and other point to the same field, i.e. More...

RecordFieldPtr< T > &	operator= (const RecordFieldPtr< T > &other)

	~RecordFieldPtr ()

void	attachToRecord (RecordInterface &record, Int whichField)
	Change our pointer to the supplied field. More...

void	attachToRecord (RecordInterface &record, const RecordFieldId &)

void	detach ()
	Point to no field in any Record. More...

T &	operator* ()
	Provide access to the field's value. More...

const T &	operator* () const

const T &	get () const

void	define (const T &value)
	Store a value in the field using redefinition. More...

const String &	comment () const
	Get the comment of this field. More...

void	setComment (const String &comment)
	Set the comment for this field. More...

Int	fieldNumber () const
	Return the fieldnumber of this field. More...

String	name () const
	Return the name of the field. More...

Bool	isAttached () const
	Is this field pointer attached to a valid record? Operations which might cause it to become detached are: More...

Public Member Functions inherited from casacore::NoticeTarget
virtual	~NoticeTarget ()
	Destructs this `NoticeTarget`. More...

Bool	isValid () const
	Returns a boolean value telling whether this `NoticeTarget` is still "valid". More...

Bool	isAttached () const
	Returns a boolean value telling whether this `NoticeTarget` is still attached to a `NoticeSource` or not. More...

void	invalidate ()
	Makes the current `NoticeTarget` "invalid". More...

Private Member Functions
virtual void	notify (const Notice &message)
	Not important for users - the mechanism by which field pointers are notified when there is a change in the record. More...

Private Attributes
T *	fieldPtr_p

RecordInterface *	parent_p

Int	fieldNumber_p

Additional Inherited Members
Protected Member Functions inherited from casacore::NoticeTarget
	NoticeTarget ()
	Creates an unlinked, "invalid" `NoticeTarget`. More...

	NoticeTarget (NoticeSource *v)
	Creates a "valid" `NoticeTarget` linked to the specified `NoticeSource`. More...

	NoticeTarget (NoticeSource &v)

	NoticeTarget (NoticeTarget &other)
	Creates a "valid" `NoticeTarget` linked to the same `NoticeSource` as the `other NoticeTarget`. More...

	NoticeTarget (NoticeTarget *other)

void	unlink ()
	Unlinks this `NoticeTarget` from its `NoticeSource`. More...

void	link (const NoticeTarget &other)
	Links this `NoticeTarget` to the same `NoticeSource` as the `other NoticeTarget`. More...

void	link (const NoticeTarget *other)

Link< NoticeTarget * > *	next ()
	Retrieves the next `NoticeTarget` in the target list of the associated `NoticeSource`. More...

const Link< NoticeTarget * > *	next () const

void	attach (NoticeSource *v)
	Adds this `NoticeTarget` to the target list in the specified `NoticeSource`, so that it will receive all notices sent out by that `NoticeSource`. More...

void	attach (NoticeSource &v)

Protected Attributes inherited from casacore::NoticeTarget
Link< NoticeTarget * > *	ilink

NoticeSource *	container

Bool	valid

Detailed Description

template<class T>
class casacore::RecordFieldPtr< T >

Access to an individual field in a record.

Intended use:

Public interface

Review Status

Reviewed By:: Mark Wieringa
Date Reviewed:: 1996/04/15
Test programs:: tRecord

Prerequisite

RecordInterface.

Etymology

RecordFieldPtr indicates that an object of this type is pointing to a field in a record.

Synopsis

RecordFieldPtr allows access to the fields in a record object. A record object is an object of a class derived from RecordInterface. RecordFieldPtr<T> objects can only be instantiated for types `T' which are valid fields of a record object (e.g. Int, float, String, Record, TableRecord). It can, however, NOT be instantiated for a Table field, because Table fields are accessed indirectly via a TableKeyword object. Table fields have to be accessed directly through the TableRecord interface.

The RecordFieldPtr is pointer-like in the sense that it points to an object that is physically inside of another object (the enclosing record object). Access to the value is obtained via the dereference operator (operator*()) to emphasize the pointer like nature of these classes.
An alternative way to get access to the values is using the functions define and get. Note that in

RecordFieldPtr<Array<Int> > field (record, fieldNumber);
Array<Int> value;
*field = value;
field.define (value);

the assignment (in line 3) and define (in line 4) are not equivalent. The assignment uses the normal Array assignment, thus it takes the Array conformance rules into account (an assign is only possible when the new array value conforms the current array value or when the current array value is empty). On the other hand, define does not take the current array value into account. Thus an array value can always be redefined.
However, note that if the field is defined with a non-fixed shape in the record description, a value must always conform that shape (in case of assignment as well as in case of define).

RecordFieldPtr is derived from NoticeTarget to get messages from the mother record class when it changes. For example, when the record is destructed, all RecordFieldPtr's pointing to that record will automatically be detached.

Example

See the example in the Record class.

Motivation

RecordFieldPtr provides a fast way to access the data in a record.

Definition at line 118 of file RecordField.h.

Constructor & Destructor Documentation

template<class T>

casacore::RecordFieldPtr< T >::RecordFieldPtr ( )

This object does not point to any field, i.e.

this->isAttached() == False;

template<class T>

casacore::RecordFieldPtr< T >::RecordFieldPtr	(	RecordInterface &	record,
		Int	whichField
	)

Attach this field pointer to the given field.

If it does not exist an exception is thrown.

template<class T>

casacore::RecordFieldPtr< T >::RecordFieldPtr	(	RecordInterface &	record,
		const RecordFieldId &
	)

template<class T>

casacore::RecordFieldPtr< T >::RecordFieldPtr ( const RecordFieldPtr< T > & other )

After calling, this and other point to the same field, i.e.

it uses reference semantics.

template<class T>

casacore::RecordFieldPtr< T >::~RecordFieldPtr ( )

Member Function Documentation

template<class T>

void casacore::RecordFieldPtr< T >::attachToRecord	(	RecordInterface &	record,
		Int	whichField
	)

Change our pointer to the supplied field.

If it doesn't exist an exception is thrown.

template<class T>

void casacore::RecordFieldPtr< T >::attachToRecord	(	RecordInterface &	record,
		const RecordFieldId &
	)

template<class T>

const String& casacore::RecordFieldPtr< T >::comment ( ) const

Get the comment of this field.

template<class T>

void casacore::RecordFieldPtr< T >::define ( const T & value )

Store a value in the field using redefinition.

Define differs from assignment w.r.t. arrays. For define a variable shaped array is deleted first with the effect that array conformance rules are not applied for them.

template<class T>

void casacore::RecordFieldPtr< T >::detach ( )

Point to no field in any Record.

template<class T>

Int casacore::RecordFieldPtr< T >::fieldNumber ( ) const

inline

Return the fieldnumber of this field.

Definition at line 176 of file RecordField.h.

template<class T>

const T& casacore::RecordFieldPtr< T >::get ( ) const

inline

Definition at line 160 of file RecordField.h.

template<class T>

Bool casacore::RecordFieldPtr< T >::isAttached ( ) const

inline

Is this field pointer attached to a valid record? Operations which might cause it to become detached are:

Destruction of the Record
Restructuring of the record.
Explicit call of the detach() member.

Definition at line 191 of file RecordField.h.

template<class T>

String casacore::RecordFieldPtr< T >::name ( ) const

inline

Return the name of the field.

Definition at line 180 of file RecordField.h.

Referenced by casacore::ColumnsIndex::copyKeyField().

template<class T>

virtual void casacore::RecordFieldPtr< T >::notify ( const Notice & message )

privatevirtual

Not important for users - the mechanism by which field pointers are notified when there is a change in the record.

Implements casacore::NoticeTarget.

template<class T>

T& casacore::RecordFieldPtr< T >::operator* ( )

Provide access to the field's value.

Note: To be sure a const function is called, it is best to use get(); For a non-const object, a non-const function is called, even if used as an rvalue;

template<class T>

const T& casacore::RecordFieldPtr< T >::operator* ( ) const

inline

Definition at line 159 of file RecordField.h.

template<class T>

RecordFieldPtr<T>& casacore::RecordFieldPtr< T >::operator= ( const RecordFieldPtr< T > & other )