_DBReplace() Function Requires Record to Be Locked

ID: Q117594

The information in this article applies to:

• Microsoft FoxPro Library Construction Kit for MS-DOS, versions 2.0, 2.5, 2.6
• Microsoft FoxPro Library Construction Kit for Windows, versions 2.5, 2.6

SUMMARY

When you are attempting to use the _DBReplace() function to place a new value in a field, _DBReplace() will return a negative integer if the current record is not locked.

_DBReplace() provides functionality similar to the FoxPro REPLACE command, but replaces the value of only one record at a time. When you attempt to use _DBReplace() to place a new value in a field, _DBReplace() will return a 0 if the replacement was successful or a negative integer whose absolute value is a FoxPro error number if the replacement was unsuccessful. Unlike the FoxPro REPLACE command, _DBReplace() must lock the current record in order to perform the replacement.

The sample code below illustrates how the _DBReplace() function works.

MORE INFORMATION

To run the sample code below, you will need to use the following syntax:

   USE <FoxPro_directory>\TUTORIAL\CUSTOMER
   =DBLOCK1(@<fieldname>,"<info_to_replace>",<work_area_number>)

NOTE: To see the error, you must comment (remark) out the following line of code as shown (this line is used to lock the record):

   /*if(_DBLock((int)parm->p[2].val.ev_long,DBL_RECORD) <= 0)
   _Execute("Wait Window 'Could not lock record'");*/

Sample Code

   #include <pro_ext.h>

   void FAR dbfunc(ParamBlk FAR *parm)
   {
      int retval=0;
      _DBUnwind((int)parm->p[2].val.ev_long);
      _DBAppend((int)parm->p[2].val.ev_long,0);

      if(_DBLock((int)parm->p[2].val.ev_long,DBL_RECORD) <= 0)
         _Execute("Wait Window 'Could not lock record'");

         /*_Execute("=RLOCK()") can also be used*/

      retval=_DBReplace(&parm->p[0].loc,&parm->p[1].val);

      if(retval<=-1)
         _Error(retval);

      _DBUnlock((int)parm->p[2].val.ev_long);
      /*_Execute("UNLOCK") can also be used*/
   }

   FoxInfo myFoxInfo[] =
   {
   {"DBLOCK1", (FPFI) dbfunc, 3, "R,C,I"}
   };

   FoxTable _FoxTable =
   {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
   };