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V_DELETE()
Delete one field from a DBV file
-------------------------------------------------------------------------------
Syntax
V_DELETE( <cPointer>,
[<nArea> | <cAlias>] ) -> cNull
Arguments
<cPointer> is a six byte pointer-field (FlexFile's version of a
memo-field).
<nArea> or <nAlias> is the DBV work area or alias with which
<cPointer> is related.
Returns
V_DELETE() returns a null string ("").
Description
V_DELETE() releases the space pointed to by <cPointer>. This space
is then available for use by the next call to V_REPLACE() or any
other function that requires DBV space. It is important to
remember that there is no V_RECALL(). That is, once a DBV has been
V_DELETE()d, that field is no longer recoverable.
When you delete a record in a DBF file and you want to be able to
recall that record (and its related VLF), do not use V_DELETE().
Instead, just DELETE the record in the DBF. When you are ready to
PACK the DBF, run a routine similar to the example below.
+------------------------ WARNING -------------------------+
| V_DELETE() deletes the data associated with <cPointer>. |
| Attempting to use <cPointer> after this function deletes |
| the data that it points to can corrupt the DBV file. |
+----------------------------------------------------------+
Notes
. V_DELETE() is permanent; there is no V_RECALL().
. V_DELETE() is not necessary before a V_REPLACE(). The second
parameter of V_REPLACE() is a pointer whose data space will be
released before the REPLACE.
Examples
// Open a DBF and its related DBV
USE dbf_file
V_USE( "dbv_file" )
// Store some data in the DBV and a pointer to the
// data in a six byte pointer-field in the DBF
REPLACE vlf WITH V_REPLACE( "This string is doomed", vlf )
// Now delete that string.
REPLACE vlf WITH V_DELETE( vlf )
// Note: It is important to erase the pointer stored in
// vlf once its data has been deleted. Because
// V_DELETE() returns a null string, REPLACEing <vlf>
// guarantees that the pointer-field vlf will be
// destroyed.
See Also:
V_REPLACE()
V_STUFF()
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