XML::Twig and Eval

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

<addr>
  <city/>
</addr>
[download]

eval {
$details{city} = $elt->first_child('address')->first_child('city')->te
+xt;
};
[download]

dies with "Can’t call method “text” on an undefined value"

shouldn't the eval block have worked and not allowing to die?

Comment on XML::Twig and Eval Select or Download Code

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Re: XML::Twig and Eval by Corion (Patriarch) on Mar 28, 2016 at 09:06 UTC
Please supply a complete, self-contained example that exhibits the problem you show. I can't replicate your problem using the following code. Most likely, you're calling `->text` on an undefined value somewhere else in your program: `use strict; use XML::Twig; warn XML::Twig->VERSION; my $twig = XML::Twig->new(); $twig->parse(<<'XML'); <addr> <city/> </addr> XML my $res = eval { $twig->first_child('address')->first_child('city')->text; }; print "Got " . $res; __END__ 3.48 at tmp.pl line 4. Use of uninitialized value $res in concatenation (.) or string at tmp. +pl line 16. Got` [download]	[reply] [d/l] [select]
Re^2: XML::Twig and Eval by Anonymous Monk on Mar 28, 2016 at 09:28 UTC
small correction,the XML is : `<address> <city/> </address>` [download] and not <addr> taking off my SIG{__DIE__} handler which was calling explicitly exit made it continue Does Eval call the DIE handler? but what if I want to continue when the code is wrapped in eval and die in all other occasions? I'm probably missing something fundamental here	[reply] [d/l]
Re^3: XML::Twig and Eval by Corion (Patriarch) on Mar 28, 2016 at 09:34 UTC
The fundamental thing is to not have a `$SIG{__DIE__}` handler at all, or at least, to not call `exit` in there. Also see `$^S` in perlvar and the discussion of it there relating to `%SIG`. Basically, what you've done is bad design and the sooner you go away from a `$SIG{__DIE__}`, the sooner your headaches will go away.	[reply] [d/l] [select]
Re^3: XML::Twig and Eval by jellisii2 (Hermit) on Mar 29, 2016 at 14:10 UTC
IIRC, in your example, there's no text on the element "city", so it will be undef. Also eval seems to indicate that if you're using `SIG{__DIE__}` within your code, you'll want a local handler inside the eval.	[reply] [d/l]