RWDBNullIndicator

Module:  DB Interface Module   Group:  Data Type

Does not inherit

• Local Index
• Synopsis
• Description
• Related Classes
• Example
• Public Constructor
• Public Member Operator

Members

operator Boolean()

RWDBNullIndicator()

#include <rw/db/nullind.h>

RWDBNullIndicator nullInd;

RWDBNullIndicator allows application code:

• to determine whether a particular piece of data extracted from an RWDBReader is NULL

• to specify whether a bound value is NULL when using an RWDBBoundExpr

An RWDBNullIndicator instance may be interpreted as a boolean value: true means a data item is NULL; false means a data item is not NULL.

RWDBNullIndicator is designed specifically to detect NULL values as they are extracted from an RWDBReader. See RWDBReader for more details.

The setting of RWDBDatabase::emptyStringIsNull can affect the way that empty strings are inserted and read. For more details, see RWDBManager::emptyStringIsNull(bool).

This code fragment selects an integer and a string from a table, and checks for NULL before processing the results:

RWDBTable myTable = myDBase.table("myTable");
RWDBSelector select = myDBase.selector();
select << myTable["id"] << myTable["name"];
RWDBReader rdr = select.reader();
int id;
RWCString name;
RWDBNullIndicator idIsNull;
RWDBNullIndicator nameIsNull;

while (rdr()) {
  rdr >> idIsNull >> id >> nameIsNull >> name;
  if (idIsNull || nameIsNull) {
    // handle NULL case
  }
  else {
    // process name and id normally
  }
} 

RWDBNullIndicator(bool value = 0);

Constructs an RWDBNullIndicator with the given initial value.

operator Boolean();

Returns the current boolean value of self.

© Copyright Rogue Wave Software, Inc. All Rights Reserved.
Rogue Wave and SourcePro are registered trademarks of Rogue Wave Software, Inc. in the United States and other countries. All other trademarks are the property of their respective owners.
Contact Rogue Wave about documentation or support issues.