Create a Dynamic List Item
In the name of Allah, Most Gracious, Most Merciful
Praise be to Allah, blessing and peace be upon our prophet
Mohammed, his family and his companions. After that,
Task
Definition: Create a
Dynamic List Item
Let's have a quite simple
application, e.g. "Club Membership" application involved two
simple tables 'YEARS' and 'MEMBERS' with two abstract column contents; id and
name column for each table individually. Now, we want to populate two list
items dynamically for each individually.
Task Execution Idea: You can follow the following logical steps to accomplish
the task safely and properly...
Procedure
''ADD_LIST_ELEMENT''Using the following procedure
Syntax
ADD_LIST_ELEMENT(list_id
ITEM, list_index VARCHAR2, list_label VARCHAR2, list_value VARCHAR2);
o
Syntax Specifications
o
list_id: Specifies the
unique ID that Oracle Forms assigns when it creates the list item.
o
Use the FIND_ITEM
built-in to return the ID to an appropriately typed variable. The data type of the ID is ITEM.
Example: v_ stage
ITEM := FIND_ITEM ('STAGE.st_id');
o
list_index: Specifies the list index value. The list index is 1 based.
o
list_label Specifies: the VARCHAR2 string that you want
displayed as the label of the list element.
o
list_value: The actual list element value you intend to
add to the list item.
o
Get_List_Element_Value:
access the current index number for each loop independently.
·
This procedure adds only a single element to a list item.
·
This is not practical for multi-list values…
So
it's more logical to think about looping through the whole database records
stored in your 'List Item' table.
Consequently, it's more appropriate
use For…. Loop structure.
· It's a dynamic
procedure; it executes run-time. You have to free the memory from any old value
to get actual and correct values result
· built-ins used as
needed:
o CLEAR_LIST
Built-in: Clears all elements from a list item. After Oracle Forms clears the
list, the list will contain only one element the 'Null' value, regardless of
the item's required property.
o GET_LIST_ELEMENT_COUNT
Built-in: Returns the the current index of the list item.
.
Task Solution:
Let's follow the above mentioned solution
idea concerning…
ADD_LIST_ELEMENT(list_id ITEM, list_index VARCHAR2, list_label VARCHAR2, list_value VARCHAR2);
Pls. Follow the logic of the following
steps to do the task safely and properly...
DECLARE
v_count NUMBER := 1 ;
CURSOR
year_cur IS SELECT year_id , year_name
FROM YEARS ORDER BY year_id;
v_ year
ITEM := FIND_ITEM ('YEARS. year_id');
CURSOR
member_cur IS SELECT member_name , member_id
FROM MEMBERS ORDER BY member_id ;
v_ member ITEM := FIND_ITEM ('STAGE. member_id');
BEGIN
CLEAR_LIST
(v_ year);
FOR m in year_cur LOOP
/**
Get_List_Element_Value access the current index number for each loop
independently.
This helps Determine
the total number of list elements. **/
ADD_LIST_ELEMENT t(v_ year , GET_LIST_ELEMENT_COUNT(v_ year)+1, m. year_name , TO_CHAR(m. year_id));
END LOOP;
/* The traditional technique */
CLEAR_LIST (v_ member);
FOR z in member_cur LOOP
ADD_LIST_ELEMENT (v_member, v_ member +1 , z. member_name
, TO_CHAR (z. member_id ));
END LOOP;
END;
Note:
o You
may face a Compilation error i.e.
FRM-30351: No list elements defined for list
item
and a run time error i.e. unable to resolve reference to the item...
o Although
you fill your list item dynamically at runtime, but the 'Null' value always
displays in the List Item.
Key Reason: By default, the
property of the list item 'Required' is set to 'YES'.
Key Solution:
*
Reset List item property: 'Required' value to
'NO'.
*
You must provide 'dummy' values: let's say 0.
Hope this helps…
My success only comes from Allah, pls. note your comments and
suggestions are great help for me in progress thanks in advance.
