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Problem with HTML::Parser

by artyom (Initiate)
on Mar 11, 2012 at 20:51 UTC ( #959019=perlquestion: print w/ replies, xml ) Need Help??
artyom has asked for the wisdom of the Perl Monks concerning the following question:

Hi guys! I have a problem. I get the error: can't call method "do" on an undefined value

#!/usr/bin/perl -w use strict; package SF; use base "HTML::Parser"; use DBI; my $f_header = 0; my $f_name = 0; my $f_description = 0; sub start { my ($self, $tag, $attr, $attrseq, $origtext) = @_ ; if ($tag eq 'header') { $f_header = 1 }; if ($tag eq 'span' && $attr->{'itemprop'} eq 'name') { $f_name = 1 + }; if ($tag eq 'a' and $f_header = 1) {my $href = $attr->{'href'} }; if ($tag eq 'p' && $attr->{'itemprop'} eq 'description') { $f_desc +ription = 1}; } sub text { my ($self, $text) = @_ ; my $name; my $href; if ($f_name = 1) {my $name = $text} if ($f_description = 1) { my $description = $text; ############## here the error ############# my $dbh->do("INSERT INTO names VALUES('$name', '$href', '$descri +ption')"); ############################################ } } sub end { my ($self, $tag, $origtext) = @_ ; if ($tag eq 'header') { $f_header = 0 } if ($tag eq 'span') { $f_name = 0 } if ($tag eq 'p') { $f_description = 0 } } package main; use strict; use DBI; use LWP::Simple; my $parcer = SF->new; my $dbh = DBI->connect("dbi:SQLite:dbname=/media/DOOMGL/perl/db.sql +t","",""); $dbh->do("DROP TABLE names"); $dbh->do("CREATE TABLE names (name, href, description)"); my $page; for ($page = 1, $page < 3, $page++) { my $url = "http://sourceforge.net/directory/os%3Alinux/freshnes +s%3Arecently-updated/?page=" . "$page"; my $content = get($url); $parcer -> parse($content); }

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Re: Problem with HTML::Parser
by tobyink (Abbot) on Mar 11, 2012 at 21:04 UTC

    Your my $dbh defines a variable called $dbh which is initially set to undef. And then you call a method ->do on it. But (unless you use autobox, which almost nobody does for production code as it's just too weird) you can't call methods on undef.

    I assume you actually want to use the $dbh variable you defined in main. Long term you want to read up about how scoping works in Perl. Short term a solution is to use $::dbh instead of $dbh, and don't use my in front of it. This acts as a global variable, so will be accessible from anywhere in your program. However, global variables are not a good idea, which is why long term you should learn how Perl scoping works.

Re: Problem with HTML::Parser
by repellent (Priest) on Mar 11, 2012 at 22:16 UTC
    Check for errors when you connect:
    my $dbfile = "/media/DOOMGL/perl/db.sqlt"; my $dbh = DBI->connect("dbi:SQLite:dbname=$dbfile", "", "") or die $DBI::errstr;

    When you fail to connect, $dbh will be undef.

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