Problem with HTML::Parser

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);
   }
[download]

Comment on Problem with HTML::Parser Download Code

Replies are listed 'Best First'.
Re: Problem with HTML::Parser by tobyink (Canon) 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.	[reply] [d/l] [select]
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 $DBI::errstr;` [download] When you fail to connect, `$dbh` will be `undef`.	[reply] [d/l] [select]


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