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V_SELECT()
Determine or select the DBV work area of a specified DBV alias
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V_SELECT( [<nNewArea>] | [<cAlias>] ) nOldArea
Arguments
<nNewArea> or <cAlias> is the new DBV area (or the new area
associated with <cAlias>).
Returns
V_SELECT() returns the old area if the area is successfully
changed or if no parameters are passed. On error (i.e. an area
beyond the bounds of the V_FILES() setting), V_SELECT() will
return a 0 and the DBV area will remain unchanged.
Description
V_SELECT() provides the functionality of a combination of
Clipper's SELECT command and SELECT() function. Specifically, it
is used to change and/or fetch the active DBV work area.
If no parameters are passed V_SELECT() parallels the Clipper
SELECT() by returning the current DBV area. If, however, a valid
DBV area or alias is passed, V_SELECT() will change the current
DBV area as Clipper's SELECT command would and then returns the
old DBV area as Clipper's SELECT() function would. This
functionality is slightly different than Clipper's SELECT() which
returns the area of the alias but does not actually change the
selected area. If you need to test for the existance of an open
file in a DBV work area, use the V_ISOPEN() function.
V_SELECT() always returns a DBV area number regardless of whether
the parameter passed was an alias or an area.
Notes
. Do not confuse Clipper's selected work area with FlexFile's;
they are mutually exclusive. For example, you can have a DBF file
open in area 2 and simultaneously have a DBV file open in
V_SELECT() == 2. Likewise, SELECT <n> has no effect on the
currently selected DBV area.
. Remember that your maximum number of open files must be set by
the V_FILES() function before V_USE()in your first DBV file. The
valid DBV areas will then be from 1 to the value you passed to
V_FILES(). See V_FILES() for more on defining the maximum number
of work areas.
Examples
// Open three DBV files in three new areas.
LOCAL nSelect
nSelect = V_SELECT(1) // Save current area and
// select area 1
V_USE( "file1", "file_one" )// Creates if not existing
V_SELECT(2)
V_USE( "file2" )
V_SELECT(0) // Select the next area
V_USE( "file3" )
? V_ALIAS() // Returns: FILE3
? V_ALIAS(1) // Returns: FILE_ONE
V_SELECT( nSelect ) // Restore the first area.
See Also:
V_ALIAS()
V_USE()
V_ISOPEN()
V_FILES()
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