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HTM::TreeBuilder, HTML::Element's look_down() method

by 7stud (Deacon)
on Oct 06, 2010 at 20:53 UTC ( #863866=perlquestion: print w/ replies, xml ) Need Help??
7stud has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

When I parse a string of html that I conjured up looking for span tags that have the attribute class="value", this code works:

use strict; use warnings; use 5.010; use LWP::Simple; use HTML::TreeBuilder; my $html =<<'END_HTML'; <html> <head><title></title></head> <body> <div><span class="value">Hi</span></div> <p>Thanks</p> <div><span class="value">Hello</span></div> </body> </html> END_HTML my $tree = HTML::TreeBuilder->new_from_content($html); my @spans = $tree->look_down(class => 'value'); for my $span (@spans) { say $span->as_trimmed_text(); } $tree->delete(); --output:-- Hi Hello

But when I unleash my code in the wild, it doesn't find the span tags:

use strict; use warnings; use 5.010; use LWP::Simple; use HTML::TreeBuilder; my $url = ' +9-02'; my $html = get($url); my $tree = HTML::TreeBuilder->new(); $tree->parse_file($html); my $span_tag = $tree->look_down( class => 'value', ); say $span_tag->as_trimmed_text(); $tree->delete(); --output:-- Can't call method "as_trimmed_text" on an undefined value at +line 41.

Can anyone see what the problem is?


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Re: HTM::TreeBuilder, HTML::Element's look_down() method
by afresh1 (Hermit) on Oct 06, 2010 at 21:11 UTC

    Pretty simple, $html is not a file, so $tree->parse_file won't work. Use $tree->parse instead.

    With some additional error checking it would have even give you a clue: $tree->parse_file($html) or die $!;


      Ah, thanks! And I could just use the same method as in the first example. The examples I looked at didn't use die(). I should have thought of that myself.

      Thanks again!

        If you had done the same as the first example, it should have worked as well, however I would still recommend checking that it was successful.

        my $tree = HTML::TreeBuilder->new_from_content($html) or die $!;

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