Apex_application.g_fXX and collection problem

Question

Hello all!
In the midst of writing my second apex application, it appears I need to use apex_application functionality to meet my requirements and am seeking assistance.
I have a table/report with a column link (item_id) and a second column (as a text field) (there are more columns displayed), but I think they are irrelevant to this situation) populated with a value QTY (c002) from a collection where c001 = item_id. What I'm attempting to do is allow someone to enter a qty in the c002 text field, apply the qty change to the collection and reload the page displaying the new quantity value in the report when the column link (image) is selected (page redirects to itself).
Since it appears that column links are not a SUBMIT, I've put my collection update plsql in a before header process. According to the debug output, this collection insert is executed long before the rendering of the report.
This is my report plsql;
declare
l_query varchar2(4000) := '';
begin
l_query := 'select i.INVENTORY_ID, col.c002, ql.QUANTITY_AVAILABLE, i.STRAIN_CODE, i.STRAIN_NAME, i.GENOTYPE, i.AGE, i.SEX, ql.ROOM_NUMBER from SM_INVENTORY i, SM_QUANTITY_LOCATION ql, apex_collections col where ql.STRAIN_ID = i.STRAIN_ID(+) and col.collection_name (+)= ''ORDER'' and col.c001 (+)= i.INVENTORY_ID';
end;
This is my update collection plsql (I don't have the insert part yet, but my collection already contains values);
declare col_item_count number;
col_seq number;
item_id number;
qty number;
begin
if apex_collection.collection_exists('ORDER') = FALSE then
apex_collection.create_collection( p_collection_name => 'ORDER');
commit;
end if;
for i in 1..apex_application.g_f01.count
loop
item_id := apex_application.g_f01(i);
qty := apex_application.g_f02(i);
select count(c001),seq_id into col_item_count, col_seq
from apex_collections
where c001 = item_id
and collection_name = 'ORDER';
group by c001, seq_id;
if col_item_count > 0 then
apex_collection.update_member(
p_collection_name => 'ORDER',
p_seq             => col_seq,
p_c001 => item_id,
p_c002 => qty);
commit;
end if;
end loop;
end;
Given all this, my collection entry is not updated with the new value of c002 displayed in my report text field.
Be advised, I've not found documentation about the apex_application package of sufficient detail to allow me to comprehend exactly what gets put into the apex_application.g_fXX values or when, but based on what I've gathered from examples/blogs, I think it contains the report in the currently rendered page, but I honestly don't know.
Given my assumptions, I'm expecting apex_application.g_f01(1) would be the first row item_id of my report and apex_application.g_f01(2) would be the first row c002 (qty from my collection) of my report. If this is correct, I would expect this would work.
What might I have missed?
Thanks!
Paul
PS. Honestly, is this methodology the only/easiest way to get my requirement/functionality to work? Is there an easier way?

Answer 1

OK, tried this - not yet successful. This is what I've got.
Classic report loaded by;
declare
l_query varchar2(4000) := '';
begin
l_query := 'select i.INVENTORY_ID, i.INVENTORY_ID inv_id_hold, col.c002, ql.QUANTITY_AVAILABLE, i.STRAIN_CODE, i.STRAIN_NAME, i.GENOTYPE, i.AGE, i.SEX, ql.ROOM_NUMBER from SM_INVENTORY i, SM_QUANTITY_LOCATION ql, apex_collections col where ql.STRAIN_ID = i.STRAIN_ID(+) and col.collection_name (+)= ''ORDER'' and col.c001 (+)= i.INVENTORY_ID';
end;
Created a "SAVE" button.
Set up column inv_id_hold as a hidden tab form element and col.c002 as a text field tab form element (item_id and qty respectively). These should now be available as apex_application.g_f01 and apex_application.g_f02 (right?).
I have this post submit plsql in a process conditioned to the "SAVE" button.
declare col_item_count number;
col_seq number;
item_id number;
qty number;
begin
if apex_collection.collection_exists('ORDER') = FALSE then
apex_collection.create_collection( p_collection_name => 'ORDER');
end if;
for i in 1..apex_application.g_f01.count
loop
item_id := apex_application.g_f01(i);
qty := apex_application.g_f02(i);
select count(c001),seq_id into col_item_count, col_seq
from apex_collections
where c001 = apex_application.g_f01(i)
and collection_name = 'ORDER';
--group by c001, seq_id;*
if col_item_count > 0 then
apex_collection.update_member(
p_collection_name => 'ORDER',
p_seq             => col_seq,
p_c001 => item_id,
p_c002 => qty);
else
apex_collection.add_member(
p_collection_name => 'ORDER',
p_c001 => item_id,
p_c002 => qty);
end if;
end loop;
end;
When I enter something in my qty column and press SAVE, I get "ORA-01403: no data found" being thrown by the plsql process (per debug). Since everything is going on "under the hood" and there is no step debugger in apex, I'm not able to see/understand the process in action and determine where the problem is occurring.
I got the idea for all of this here - http://apex.oracle.com/pls/otn/f?p=39839:3:5596350954563087::NO which is the shopping cart page of the online store application. But I'm trying to get the quantity edit portion to work on the inventory listing (so a customer can add items to an order simply by providing qty input for a particular line item(s) and saving).
Any advice?
Can you write an order processing system in apex that uses a collection to store line items?