Beefy Boxes and Bandwidth Generously Provided by pair Networks
Think about Loose Coupling
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Hi all,

Warning: I have never used eval to error-handle before. I've been avoiding it for more than a year now. I thought I had seen enough examples to be sure how it worked. Obviously I was wrong.

I have code that both creates and loops over objects. The details of the objects shouldn't matter too much, I think. I normally use this object like so:

my $object = My::Class->new(); while (my $value = $object->next_val() ) { # do cool stuff }

But I am using this object in a CGI, and I thought I had best catch problems gracefully, with some nice error explanation rather than just a 500 error. I wanted to use syntax like:

my $object = My::Class->new(); while (my $value = eval { $object->next_val() } ) { if ($@) { print "Error: $@\n"; next(); } # do cool stuff }

This didn't quite work as I expected, though, and I'm not sure why. This code works just fine if the eval succeeds, but it never gets to my error-handling code, even if the eval fails. I have also tested adding the same error-handling code after my while loop.

So, I seem to have some misconception about how eval should behave: can anybody point it out to me, please?


In reply to Error Handling Misconception by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others contemplating the Monastery: (4)
    As of 2020-06-05 06:24 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?
      Do you really want to know if there is extraterrestrial life?



      Results (35 votes). Check out past polls.

      Notices?