RWDBNullIndicator Class Reference
[Data Types]

Provides a way to determine whether some given data is NULL. More...

#include <rw/db/nullind.h>

List of all members.

Public Member Functions
	RWDBNullIndicator (bool value=0)
	operator bool () const

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Detailed Description

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.

Synopsis

 #include <rw/db/nullind.h>

 RWDBNullIndicator nullInd;

Related Classes

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).

Examples

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
   }
 }

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Constructor & Destructor Documentation

RWDBNullIndicator::RWDBNullIndicator

(

bool

value = 0

)

[inline]

Constructs an RWDBNullIndicator with the given initial value.

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Member Function Documentation

RWDBNullIndicator::operator bool

(

)

const [inline]

Returns the current boolean value of self.