Error Handling.

fjaenale has asked for the wisdom of the Perl Monks concerning the following question:

Hello:
I have a question about this piece of code (I know is the same as my last post):

   $self->{ftp}->put($origin, $target) or
          $msg = $self->{ftp}->message(),
          $cod = $self->{ftp}->code(),
          print ("$cod: $msg\n"),
          return 1;
[download]

-- EDIT: Sorry there is a mistake on the print intruction. I am adding the parenthesis, in the real code it calls a function.--

I just want to know if the way I handle the error is correct. After thte "or" I separate the instructions with ","; I have been told that this is a risky practice. I just want to know if this is really a risky practice or is ok to use the "," as separators.

In case there is a better less risky way, what would be that way?.

Thank you very much,
Francisco Jaen
www.cgi.com

Comment on Error Handling. Download Code

Replies are listed 'Best First'.
Re: Error Handling. by ysth (Canon) on Sep 28, 2004 at 07:25 UTC
It's only risky if you don't understand the precedence of the different operators you use or call functions that take a list without supplying parentheses. In your sample code, everything is great until the print; because you don't say `print("$cod: $msg\n"), return 1;` [download] it will assume `print("$cod: $msg\n", return 1)` so the return will actually happen as it is trying to build the list of parameters for print, and the print itself will never be issued. This kind of mistake is a pain to find; since you've done it once, I'd eschew this style of error handling and just go with: `if (error condition) { set stuff print message return }` [download]	[reply] [d/l] [select]
Re: Error Handling. by bobf (Monsignor) on Sep 28, 2004 at 07:41 UTC
You could use an 'if' and set error flags (or test the error condition directly), or you could use a `do{ };` block, which would avoid having to keep track of precedence (as ysth pointed out): `$self->{ftp}->put($origin, $target) or do { $msg = $self->{ftp}->message(); $cod = $self->{ftp}->code(); print ("$cod: $msg\n"); return 1; };` [download]	[reply] [d/l] [select]
Unless.. by htoug (Deacon) on Sep 28, 2004 at 07:59 UTC
I'd do it with an `unless` statement. It allows you to keep things almost as with the `or` but without the pitfalls. `unless ($self->{ftp}->put($origin, $target)) { $msg = $self->{ftp}->message(); $cod = $self->{ftp}->code(); print "$cod: $msg\n"; return 1; }` [download] You can even leave out the parenthesis on the `print` statement ;-)	[reply] [d/l]


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