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PL/SQL Forward
Declarations
Oracle Tips by
Burleson
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In the event that you have more than one local declared procedure
or function within a block of PL/SQL and the procedures must reference
each other, you won’t be able to compile your code without getting an
error. Each local procedure must be declared before the other.
To get around this problem, you can use a forward declaration
to specify the interface for the procedures. This will allow your
PL/SQL block to compile without errors. Listing 4.4 illustrates the
use of a forward declaration.
Listing 4.4 Using a forward declaration for a local
procedure.
CREATE OR REPLACE
PROCEDURE Calculate_Lot_Size (nWidth IN number,
nLength IN number,
nLotSize OUT number)
IS
PROCEDURE Convert_Feet_To_Yards (nFeet IN number,
nYards IN OUT number);
PROCEDURE Convert_Yards_To_Feet (nYards IN number,
nFeet IN OUT number)
IS
nCheckCalc number := 0;
xBAD_CALCULATION EXCEPTION;
BEGIN
nFeet := nYards * 3;
Convert_Feet_To_Yards (nFeet => nFeet,
nYards => iCheckCalc);
IF (nCheckCalc != nYards) THEN
RAISE xBAD_CALCULATION;
END IF;
END Convert_Yards_To_Feet;
PROCEDURE Convert_Feet_To_Yards (nFeet IN number,
nYards IN OUT number)
IS
nCheckCalc number := 0;
xBAD_CALCULATION EXCEPTION;
BEGIN
nYards := nFeet/3;
Convert_Yards_To_Feet (nYards => nYards,
nFeet => iCheckCalc);
IF (nCheckCalc != nFeet) THEN
RAISE xBAD_CALCULATION;
END IF;
END Convert_Feet_To_Yards;
BEGIN
<statements>
END Calculate_Lot_Size;
/
In this example, the first highlighted portion of the code is the
forward declaration of the Convert_Feet_To_Yards() procedure,
the second highlighted portion of the code is the call to the
procedure, and the last highlighted portion of the code is the
definition of the procedure’s logic. If the forward declaration of the
procedure Convert_Feet_To_Yards() were removed from this
example, the code would not compile.
This is an excerpt from the book "High Performance Oracle
Database Automation" by Jonathan Ingram and Donald K.
Burleson, Series Editor. |
