ID: Q123206
The information in this article applies to:
The Library Construction Kit (LCK) _FindVar() function returns incorrect results if the second parameter of the LCK _FindVar() function is specified to be a work-area number other than the currently selected work area.
Use the LCK _Execute() function to select the work area and then use _FindVar() function to find the value of the field in the selected work area. The code in the More Information section demonstrates this workaround.
Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.
The LCK _FindVar() function provides a way to initialize the Locator structure with information about a variable or field. The _FindVar() function has three parameters:
int _FindVar(NTI nti, int where, Locator FAR *loc)
/* Date: 09/08/94
Purpose: To pass the work area number and the field name to the
function XREAD and return the corresponding value.
FoxPro Code:
CLEAR
SELECT 1
USE customer
SELECT 2
USE invoices
SELECT 1
SET LIBRARY TO test.dll && This is the name of .dll
&& created by this C program.
=XREAD(2,"itotal")
SET LIBRARY TO
CLOSE ALL
*/
#include <pro_ext.h>
#include <stdlib.h>
#include <string.h>
void FAR readfield(ParamBlk FAR *parm)
long int work_area;
NTI nti;
char FAR * field_name;
Locator loc;
Value val;
char FAR *select_cmd="SELECT ";
Value current_wa; /* used to store current work area */
long int c_wa;
char buffer[4];
if (parm->p[0].val.ev_type='I')
work_area=parm->p[0].val.ev_long;
if (parm->p[1].val.ev_type='C')
{
//Null terminate character string that has field name.
if (!_SetHandSize(parm->p[1].val.ev_handle,parm->
p[1].val.ev_length+1))
{
_Error(182); //Insufficient Memory
}
_HLock(parm->p[1].val.ev_handle);
field_name=(char FAR *)_HandToPtr(parm->
p[1].val.ev_handle);
field_name[parm->p[1].val.ev_length]='\0';
// Display string Value
_PutStr("Field Name: ");
_PutStr(field_name);
//Carrage Return and Line Feed
_PutChr(13);
_PutChr(10);
/* Store current work area. */
_Evaluate(¤t_wa,"select(alias())");
c_wa=current_wa.ev_long;
_PutStr("Current Work Area: ");
_PutChr(c_wa+48); /* In our test workarea < 3 */
_PutStr("\n");
strcat(select_cmd,_itoa((int)work_area,buffer,10));
_PutStr("Select Command: ");
_PutStr(select_cmd);
_PutStr("\n");
_Execute(select_cmd);
_StrCpy(select_cmd,"SELECT "); /* Reset Select
Command */
nti=_NameTableIndex(field_name);
if(nti == -1)
{
_HUnLock(parm->p[1].val.ev_handle);
_UserError("Cannot find variable in named table.");
}
if (_FindVar(nti,0,&loc))
{
_Load(&loc,&val);
//Display value returned by _FindVar()
_PutStr("Value Returned by _FindVar() : ");
_PutValue(&val);
}
else
{
_PutStr("\nVariable does not exist!!!!");
}
/* Return to the previously selected work area. */
strcat(select_cmd,_itoa((int)c_wa,buffer,10));
_Execute(select_cmd);
//Unlock Handle - send address back to heap
_HUnLock(parm->p[1].val.ev_handle);
}
}
/* First parameter is the Work Area Number
Second parameter is the Field Name
*/
{"XREAD",(FPFI)readfield,2,"I,C"},
FoxTable _FoxTable={
(FoxTable FAR *)0,sizeof(myFoxInfo)/sizeof(FoxInfo),myFoxInfo
/* Purpose: To pass the work area number and the field name to the
function XREAD and return the corresponding value
CLEAR
SELECT 1
USE customer
SELECT 2
USE invoices
SELECT 1
SET LIBRARY TO test.dll && Where test is the name of this C
&& program when compiled.
=XREAD(2,"itotal")
SET LIBRARY TO
CLOSE ALL
*/
#include <pro_ext.h>
void FAR readfield(ParamBlk FAR *parm)
long int work_area;
NTI nti;
char FAR * field_name;
Locator loc;
Value val;
if (parm->p[0].val.ev_type='I')
work_area=parm->p[0].val.ev_long;
if (parm->p[1].val.ev_type='C')
{
//Null terminate character string that has field name.
if (!_SetHandSize(parm->p[1].val.ev_handle,parm->
p[1].val.ev_length+1))
{
_Error(182); //Insufficient Memory
}
_HLock(parm->p[1].val.ev_handle);
field_name=(char FAR *)_HandToPtr(parm->p[1].val.ev_handle);
field_name[parm->p[1].val.ev_length]='\0';
// Display string Value
_PutStr("Field Name: ");
_PutStr(field_name);
//Carrage Return and Line Feed
_PutChr(13);
_PutChr(10);
nti=_NameTableIndex(field_name);
if(nti == -1)
{
_HUnLock(parm->p[1].val.ev_handle);
_UserError("Cannot find variable in named table.");
}
//Display number returned by nti
_PutStr(" A Value Was Returned by _NameTableIndex().");
_PutChr(13);
_PutChr(10);
if (_FindVar(nti,(int)work_area,&loc))
{
_PutStr("Variable does exist.\n");
_Load(&loc,&val);
//Display value returned by _FindVar()
_PutStr("Value Returned by _FindVar() : ");
_PutValue(&val);
}
else
{
_PutStr("\nVariable does not exist!!!!");
}
//Unlock Handle - send address back to heap
_HUnLock(parm->p[1].val.ev_handle);
}
/* First parameter is the Work Area Number
Second parameter is the Field Name
*/
{"XREAD",(FPFI)readfield,2,"I,C"},
FoxTable _FoxTable={
(FoxTable FAR *)0,sizeof(myFoxInfo)/sizeof(FoxInfo),myFoxInfo
FoxPro Library Construction Kit "Developer's Guide," _FindVar() section.
Additional reference words: FoxWin LCK 2.50 2.50a 2.50b 2.60 2.60a buglist2.50 buglist2.50a buglist2.50b buglist2.60 buglist2.60a KBCategory: kbtool kbbuglist KBSubcategory: FxtoolLck
Last Reviewed: June 27, 1995