Apple

On Aug 11, 2005, at 7:15 AM, Mark J. Reed wrote:

DIdn't see anything on this topic in my copy of Neuberg. Is there any way to test to see if a variable has been defined? This code snippet works great if the global variable _ has been assigned a value. If not, however, it fails when I try to save a copy. Is there any sort of test I can use which will test for the variable being defined without blowing up? Or any sort of exception-catching mechanism to intercept the blowup before it happens?

global _
set saved_ to _
(* do stuff with _ *)
set _ to saved_

It doesn't blow up for me. When I try to run the script, I get an error at the second line saying that "_" has not been defined. That happens whenever I run the script; before saving, after saving, or after quitting and opening the saved file.

That is how it is supposed to work.

If you are trying to run the script without assigning a value to the variable, then you need to trap the error.

global _

try

set saved_ to _

on error number num

if num is -2753 then

set saved_ to null

end if

end try

(* do stuff with _ *)

set _ to saved_

-- Michelle

"Where is the wisdom we have lost in knowledge?

Where is the knowledge we have lost in information?

Where is the information we have lost in data?"

T.S. Eliot (1915)

References:
	>Test for existence of a variable? (From: "Mark J. Reed" <email@hidden>)