[REBOL] Re: Don't understand "try" and "disarm"
From: swhite::ci::bloomington::mn::us at: 14-Mar-2006 10:46
Thank you. It did not register in my old-fashioned brain that one could
do an existence check across the network. I tossed out all the "try"
stuff and just checked to see if the source file and the target
directory existed before I allowed any file transfer.
This "set-word" concept is a bit confusing, but I am going to wait with
my criticism of the REBOL documentation until I have re-read it, plus
the two books I have purchased. Then I'll complain.
>>> greggirwin-mindspring.com 3/14/2006 10:12 AM >>>
Hi Steven,
This is pretty easy, once you know the trick. First, though, I'll ask
if you've looked into using EXISTS? ?
SW> TRANSFER-FILE: does [
SW> either error? FTP-RESULT: try [
SW> ;;;; read %nonexistent.txt ;;;;; this file does NOT exist
SW> ;;;; read %fileexists.txt ;;;;; This file DOES exist
SW> write %tempfile.txt read %fileexists.txt
SW> ]
TRY returns the result of the block evaluation; in this case, the
result of WRITE. Fire up a console and see what WRITE returns. Now,
try assigning that value using a set-word!, like the above code.
What's happening is that WRITE returns an unset! value, which doesn't
work directly with set-word! syntax. You need to use SET/ANY. e.g.:
either error? set/any 'FTP-RESULT try [
write %tempfile.txt read %fileexists.txt
]
HTH!
-- Gregg
