Form Level Variable

Question

I want to declare a form level variable and want to assign a value at WHEN-NEW-FORM-INSTANCE trigger and i want to use the same value in Program units as well as other form level and block level triggers. How to achieve this? Do i need to refer the variable with :Symbol? Thanks!

Answer 1

Chris,
There are a couple of ways to do this. As Ammad suggested, you can use a Global variable, but as you point out - Globals are visible to your Forms session unless you destroy the global. You can also use a Parameter as you have done or you can use a Control Block with a block item that will accept the type of data that will be stored in the variable. There are limitations with each of these options however.
With Globals, all variables are of CHAR datatype and are limited to 4000 bytes in Forms 10g and higher and 255 in Form 9i and lower. Any non-character value stored in a global must be converted back to it's native datatype when you read the value to ensure it is evaluated correctly. When globals are declared, they always reserve the max amount of memory needed to support the 255 or 4000 characters. If you use Globals, it is a good habit to use the Erase() built-in to destroy the Global when you are finished with it. Also with Globals it is possible to get a Runtime error if the Global has not been initialized before you reference it, but will NOT produce a compile time error.
Parameters and Control Block items are a little more flexible in that you can define the parameter's datatype as CHAR, DATE or NUMBER (check Forms Help for the max datatype values they can store). Parameters and Control block items also have properties which means they take up more memory resources because the properties of these items have to be loaded into memory in addition to the data.
I would recommend using Parameters over Globals for Forms specific variables because you have greater flexibility with the data types supported, however, I personally prefer to use a Forms Package Specification with Package Variables declared as this more flexible and only allocates the amount of memory needed to support the variable. When I have a situation that requires a variable be visible to the entire form, but doesn't need to be Global to the session, I will create a Package Spec called FORM_VARS in the Program Units node of the Object Navigator and declare the variables I need. I do not create a Package Body. For example:
PACKAGE FORM_VARS IS
   n_User_ID      NUMBER;
   v_User_Name  VARCHAR2(25);
END;You then reference the variables the same as you would for any Forms program unit.
BEGIN
   Forms_Vars.n_User_ID := 1234546;
   Forms_Vars.v_User_Name := 'John Doe';
END;Hope this helps,
Craig B-)
If someone's response is helpful or correct, please mark it accordingly.
Edited by: CraigB on Jun 28, 2010 11:17 AM