with vars, end with

[Ronald Anusiewicz]

I'm trying to figure out what:

with vars....end with

does in an xbasic script. I've been searching and I must be looking in the wrong places.
I've seen this in Dr. Waynes codes and I know he explained it somewhere, I just can't find it now.

Ron

[Stan Mathews]

Re: with vars, end with

Do the examples in the documentation not work for you?

Set the default name space to global_variables(), then define several global variables.
 





WITH global_variables()

    Firstname = "Jonathan"

    Lastname = "Swift"

    Address = "2 Bigelow St."

    City = "Cambridge"

    State = "MA"

    Zip = "02139"

END WITH
 

Set the default name space to local variables on the Customer form, then set the value of several local variables on the Customer form.
 





WITH :customer.variables()

    Start_Date = {1/1/99}

    End_Date = {1/31/99}

END WITH
 

Set the default name space to the customer dot variable.
 





WITH customer

    firstname = "John"

    lastname = "Smith"

END WITH

[Ray in Capetown]

Re: with vars, end with

Useful Stan. I didn't know it covered dot variables.

[Ronald Anusiewicz]

Re: with vars, end with

Stan, thank you for your reply. I now see that I was searching for the wrong thing. I have found with…end with.

I’ve used variables for years, but I don’t understand the need, purpose of name spaces. What’s the advantage of using name spaces over a local, shared variable or a global variable?

Ron

[Stan Mathews]

Re: with vars, end with

Having used variables for years there is probably no advantage for you. For someone starting with Alpha now, it would probably add some clarity.

The use of with....end with seems to me to be similar to the coding style in VB for Excel macros.

[Finian Lennon]

Re: with vars, end with

Here's where, why I use it. I hate shared variables. There were many times when I used them that I could not figure out a variable scope problem and would resort to making the variable global instead. Shared variables are especially confusing (to me anyway) in a long script that may call functions that reference the variables used in the script. My preference is to dimension a variable as local, once, at the start of the script but reference it anywhere within this script.

So I begin almost every script with the line

lv = local_variables()
'and such as 
dim fn as c
dim ln as c

Then, when I need to write an embedded function that will use any of those dimensioned variables, I will define the function as

Function DoThis as C (lv as p)
with lv

'now it is possible to refer to fn and ln without further definition
'nor is it necessary to use arguments in the function to pass variable values in unless for some reason you want to.
'so, for example, I can now use fn and ln as variables in an xdialog defined here
'and then refer to those values after the xdialog has closed 

End With
End Function

and call it in the script with

DoThis(lv)

You can achieve something similar (without using With .. End With) by using script_play_local("ThisScript") to call a script where "ThisScript" will inherit the variables defined in the calling script.


This helps me keep things straight in a way that no other technique I have tried was able to do. It's a matter of personal preference.

[Ronald Anusiewicz]

Re: with vars, end with

Thank you Finian.

You have explained it very well and now when I read Dr. Waynes code, it all makes sense.

Ron

[martinwcole]

Re: with vars, end with

I oftern write a script, that has multiple functions also located in the script
then if I dim variables as shared at the top of the script, they are available for the functons - otherwise they are not

[Ray in Capetown]

Re: with vars, end with

For me the usefulness was enabling "reaching across" to other forms, for example, to address large groups of variables.
Now I've learnt it can work to simplify working with multiple blob or dot vars

[MoGrace]

Re: with vars, end with

Do the examples in the documentation not work for you?

Set the default name space to global_variables(), then define several global variables.
 

WITH global_variables()

    Firstname = "Jonathan"

    Lastname = "Swift"

    Address = "2 Bigelow St."

    City = "Cambridge"

    State = "MA"

    Zip = "02139"

END WITH
 

Set the default name space to local variables on the Customer form, then set the value of several local variables on the Customer form.
 

WITH :customer.variables()

    Start_Date = {1/1/99}

    End_Date = {1/31/99}

END WITH
 
Set the default name space to the customer dot variable.
 
WITH customer

    firstname = "John"

    lastname = "Smith"

END WITH

When I see WITH VARS (the question in the OP) in some script, I expect to see VARS defined in the script as a pointer to local_variables(). But I am looking at a learning xdialog script by Selwyn at the moment that uses this and the only pointer was a parameter in an embedded function (vars as p). And the only place 'local_variables()' appeared was inside a comment section.

So when the help says 'set the default name space on a form' - which example is doing that?

[Stan Mathews]

Re: with vars, end with

So when the help says 'set the default name space on a form' - which example is doing that

Set the default name space to local variables on the Customer form, then set the value of several local variables on the Customer form.


WITH :customer.variables()

:Customer is the form object, variables() is the namespace for local variables.



WITH :customer.variables()

Start_Date = {1/1/99}

End_Date = {1/31/99}

END WITH

is equivalent to

:customer.variables().Start_Date = {1/1/99}

:customer.variables().End_Date = {1/31/99}


more or less a shortcut.

[MoGrace]

Re: with vars, end with

Stan,
I'll check the script again and see if I can find it. But I don't think a form.variables() is there because it was being used to create a MDI window...

[MoGrace]

Re: with vars, end with

Relative to this thread I hope: is it possible to set a variable before calling a function that calls another function where that variable is defined? I believe that when a function has parameters, the variables' scope is shared isn't it - or not?

My example:

dim shared showlist as n = 1
XmlMenu()

'xmlmenu() calls Get_menu(showlist as n)

[MoGrace]

Re: with vars, end with

This example from the help on session_variables() looks promising, but it is for a form - how would I adapt it?

dim ptr as P
dim var as P
dim s as N
ptr = form.load("Customer Information")
s = ptr.SessionHandle()
var = session_variables(s)
? var.A_DB_CURRENT_PATH   -> "c:\databases\expressions test\"

[MoGrace]

Re: with vars, end with

This thread always shows up whenever I am reviewing variable scoping and thought I would add a note.

I was working on changing an xdialog function into a dockable toolbar and found that in the toolbar, the variables were misbehaving when used inside
a5_get_filter()

And by misbehaving, I mean the filter expression genie would not open when SOME sets were selected. Which after reviewing this thread, I tried making those variables shared in the toolbar and that seemed to fix it. Then I realized I just needed to add the WITH VARS...END WITH to my function so the xdialog could see the local variables.

Hopefully now I won't forget it again!