Global variable declaration

[Jesse Sanders]

I am creating a form that has several xbasic scripts that need to talk to on another via variables. Now there are several ways to declare global variables in alpha 5 and I wonder if they are all equivelent and how they differ.

One is using the variable declaration button on the task bar.
Two is on the varaibles tab of the script editor.
Third is as a Dim global in a script.

What is the difference?
When would you use one over the other?

[Jim Chapman]

RE: Global variable declaration

Hi Jesse,

>>What is the difference?
When would you use one over the other?

[Geoffrey Hollander]

RE: Global variable declaration

Jesse,

Jim is right; you should only use global variables when the input is dynamic (input -- ostensibly from the user -- is needed by the script to continue processing) or when passing a value around, such as field names for report content, and they need to be persistent throughout your application.

Than being said, I use 200-300+ global variables in an application without mishap. (This is because I have no way of anticipating the kind of table that I'll be working on.)

It is, as Jim said, a good idea to load them in your autoexec script because, once they're declared, you can use them in several different scripts interchangeably, without having to be sure the are declared in each. (This is especially true if the scrips might be run in different combinations and sequences at various times.)

It is also a good idea to declare global variables BEFORE you start designing forms, reports, etc. so that you can treat them just like "real" objects, like when placing a field on a form. It will save you a lot of time.

Note also, that if you are going to use a lot of GV's, it's a good idea to set up some sort of standardized naming convention so they don't get tangled up, oh, and comment them heavily in the autoexec script as well (in six months you'll thank me)...

Good question. Good luck.

Best regards,

Geoff Hollander

[Greg Fong]

RE: Global variable declaration

In a networking environment with a lot of users do you have problems with global variables messing things up? For example if you have a bunch of people doing data entry using essentially the same dataentry form and lets say that global variables are used to hold and transform values within these forms, does A5 keep these values related to each user or is it possible for the values to change depending of which user has control of it at any particular time?

This is my one greatest paranoia about using global variables although up to this point I havn't used any session or layout level variables. The fact is that I can't get my head around how to use them.

I have a sales entryform that contains a button that pops up a small form that is linked to my inventory table. This small form is used to allow the user to reserve or hold a quantity of stock for a pending order. The form displays quantity on_hand, the current number of items on hold and other inventory related data. I also have two variable fields on the form v_new_hold and v_hold_more both are global. The idea is that the user upon opening this form would enter into "v_hold_more" the number of items he would like to add to the current hold level. In the onchange event of v_hold_more this amount would be added to the current level and the amount would end up in v_new_hold
When this form is closed the global variable v_hold_more is picked up by the calling form. When the user decides to save the sales order entry, I insert the v_hold_more value to the current sales order to show how many items were held and I add the value of v_hold_more to the hold field on the inventory table.

The question is, how do you set up v_hold_more as anything other than a global variable so that it can be passed from the "Hold" form back to the calling "Salesentry" form.

I've spent countless hours at this and I feel that I need one of those whack on the side of the head enlightenments.

[Finian Lennon]

RE: Global variable declaration

Greg:

Each Alpha session running on a network is "insulated" from the other so that the global variables in each session is independent of the global variables in all other sessions. Obviously the sessions interact to a degree as records are entered and changed but the database engine and the network OS take care of that. Like Geoff, I use globals pretty extensively and providing you don't get careless with naming you shouldn't have a problem.

In the case you describe you can certainly use a global variable, though it is not necessary to do so. You can pass form variable values back and forth by addressing the layout variable object on each form. The following is a pretty crude example: this code could be on a button on FormA. FormA has a numeric variable object called nVar and FormB has an identially defined numeric variable object also called nVar, then

f1=parentform.this
f2=Obj("FormB")
if is_object(f2) then
goto nextstep
else
f2=form.load("FormB")
f2.show()
f2.activate()
end if
nextstep:
f2:nVar.value=f2:nVar.value+f1:nVar.value
f2.show()
f2.activate()
f2:nVar.refresh()
would add the value of the variable on Form A to the variable on Form B where each nVar is defined as a layout variable, then show the results.

Finian

[Jesse]

RE: Global variable declaration

Thanks,
This is good advice.

Jesse

[Jesse]

RE: Global variable declaration

I'll note them well.
I have forgotten to make it clear what a function is to do before,
and spent some time reading the code till it made sense. So, I can relate

Good Ideas.

I have an Idea what is happening so I think I know why one variable is not being
updated. (The OnTime event is starting over before the last OnTime event is finished, OOPS). I can Fix that.

Thanks Again.

Jesse