Getting the error Reference to uninitialized collection to associative arrays - oracle

Question

I am using associative arrays in a package I am creating and I get the error ORA-06531: Reference to uninitialized collection if I try to get the count (TBL.COUNT) before I have bulk collected into the array.
I have found that I can use EXISTS(1) to check if there is something there instead of the count but if I am not bulk collecting into it, how do I get the index I need to use for the next row?
loc_idx := TBL.COUNT;
OR
TBL(TBL.COUNT+1) := blah;
My thought was that you didn't need to initialize associative arrays unlike Nested tables and varrays
Here is an example of one I am using
TYPE invc_ln_item_type IS TABLE OF invc_ln_item%ROWTYPE;
invc_ln_item_tbl invc_ln_item_type;
used as an input to the following proc
PROCEDURE CREATE_INVC_LN_ITEM(P_LN_ITEM_TYPE_CD IN
invc_ln_item.ln_item_type_cd%TYPE,
P_LN_ITEM_SBTYPE_CD IN
invc_ln_item.ln_item_sbtype_cd%TYPE,
P_INVC_PK IN invc.invc_pk%TYPE,
P_INVC_LN_ITEM_TBL IN OUT
invc_ln_item_type)
IS
loc_inv_ln_item_rec INVC_LN_ITEM%ROWTYPE;
loc_idx NUMBER;
BEGIN
loc_idx := P_INVC_LN_ITEM_TBL.COUNT + 1;
INSERT INTO APP.INVC_LN_ITEM (INVC_LN_ITEM_PK,
INSRT_DT,
INSRT_USER,
LAST_UPDT_DT,
LAST_UPDT_USER,
LN_ITEM_TYPE_CD,
LN_ITEM_SBTYPE_CD,
INVC_PK,
UNITS,
AMT)
VALUES (null,
null,
null,
null,
null,
P_LN_ITEM_TYPE_CD,
P_LN_ITEM_SBTYPE_CD,
P_INVC_PK,
0,
0)
RETURNING INVC_LN_ITEM_PK,
INSRT_DT,
INSRT_USER,
LAST_UPDT_DT,
LAST_UPDT_USER,
LN_ITEM_TYPE_CD,
LN_ITEM_SBTYPE_CD,
INVC_PK,
UNITS,
AMT
INTO loc_inv_ln_item_rec;
P_INVC_LN_ITEM_TBL(loc_idx) := loc_inv_ln_item_rec;
END;
Then gets called like
CREATE_INVC_LN_ITEM(P_BILLG_PRFL_LN_ITEM_REC.ln_item_type_cd,
billg_prfl_ln_item_sbtype_tbl(c).ln_item_sbtype_cd,
invc_rec.invc_pk,
invc_ln_item_tbl);
The errors in the case above occurs at:
loc_idx := P_INVC_LN_ITEM_TBL.COUNT + 1;
[Error] Execution (39: 1): ORA-06531: Reference to uninitialized collection

Answer 1

There is not an incrementing index for an associative array. You do not need to initialise an associative array and using array.COUNT will not raise an exception with an associative array (unlike for collections).
DECLARE
TYPE arraytype IS TABLE OF VARCHAR2(20) INDEX BY VARCHAR2(2);
array arraytype;
idx VARCHAR2(2);
BEGIN
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 0
array('A') := 'AAAA';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 1
array(array.COUNT + 1) := 'BBBB';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 2
array('7') := 'DDDD';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 3
idx := array.FIRST;
WHILE idx IS NOT NULL LOOP
DBMS_OUTPUT.PUT_LINE( idx || ' - ' || array(idx) );
idx := array.NEXT( idx );
END LOOP;
END;
/
If you are expecting to use an incrementing index then you need to consider whether an associative array is the correct type to be using and whether a collection or a VARRAY would be better.
If you are using collections (not associative arrays):
DECLARE
TYPE arraytype IS TABLE OF VARCHAR2(20);
array arraytype;
BEGIN
array := arraytype(); -- Initialise
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 0
array.EXTEND; -- Extend by 1 element
array(1) := 'AAAA';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 1
array.EXTEND(1); -- Number of elements to extend by
array(array.COUNT) := 'BBBB';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 2
array.EXTEND;
array(3) := 'DDDD';
DBMS_OUTPUT.PUT_LINE( array.COUNT ); -- 3
FOR idx IN 1 .. array.COUNT LOOP
DBMS_OUTPUT.PUT_LINE( idx || ' - ' || array(idx) );
END LOOP;
END;
/