period in strings

[kc]

Hi! i'm relatively new to perl and keep getting this warning:

Use of uninitialized value in string eq at test.pl line 40.

foreach my $key (@keys) {
if (($key->{'att'}->{'for'} eq 'node') && ($key->{'att'}->{'yfiles.type'} eq 'nodegraphics')){ #line 40 here
$nodeD = $key->{'att'}->{'id'};
} elsif (($key->{'att'}->{'for'} eq 'edge') && ($key->{'att'}->{'yfiles.type'} eq 'edgegraphics')){
$edgeD = $key->{'att'}->{'id'};
}
}
i wonder if it is the period in the 'yfiles.type' that is causing the warning and how i can get rid of it?

[kennethk]

The issue is not the period, per se, but that the nested hash structure is uninitialized for either $key->{'att'}->{'for'} or $key->{'att'}->{'yfiles.type'}. I would suggest you use Data::Dumper to examine your @keys structure before you reach the loop to see if the data content matches your expectations. Inserting the following before your foreach loop should suffice:

use Data::Dumper;
print Dumper \@keys;

On a side note, please wrap posted code in <code> tags to maintain formatting, as per Writeup Formatting Tips or Markup in the Monastery. And welcome to the Monastery.

[apl]

You never need to "wonder". Googling Perl uninitialized value would have pointed you towards something like this.

[doug]

Ouch, That is ugly. Next time try something like

 my %field = %{ $key->{att} };

or maybe

 my $for = $key->{att}->{'for'};
 my $type = $key->{att}->{yfiles.type};

to reduce the amount of dereferencing. It is really easy to misread all that stuff.

- doug