access object values

[averlon]

Hi, I am strugling to access the values of an object.

Net::DNS::Packet=HASH(0x560a2c51be98)
   'additional' => ARRAY(0x560a2c643678)
        empty array
   'answer' => ARRAY(0x560a2c4ea600)
      0  Net::DNS::RR::PTR=HASH(0x560a2c650780)
         'class' => 1
         'owner' => Net::DNS::DomainName1035=HASH(0x560a2c6504f8)
            'label' => ARRAY(0x560a2c6506d8)
                 empty array
            'origin' => Net::DNS::DomainName=HASH(0x560a2c6507b0)
               'label' => ARRAY(0x560a2c650798)
                  0  20
                  1  171
                  2  191
                  3  185
                  4  'in-addr'
                  5  'arpa'
         'ptrdname' => Net::DNS::DomainName1035=HASH(0x560a2c650960)
            'label' => ARRAY(0x560a2c650948)
               0  20
               1  'bl'
               2  'bot'
               3  'semrush'
               4  'com'
         'rdlength' => 23
         'ttl' => 273
         'type' => 12
   'authority' => ARRAY(0x560a2c63e350)
        empty array
   'count' => ARRAY(0x560a2c6503c0)
      0  1
      1  1
      2  0
      3  0
   'id' => 31152
   'question' => ARRAY(0x560a2c51c270)
      0  Net::DNS::Question=HASH(0x560a2c6438e8)
         'qclass' => 1
         'qname' => Net::DNS::DomainName1035=HASH(0x560a2c63edd0)
            'label' => ARRAY(0x560a2c650480)
               0  20
               1  171
               2  191
               3  185
               4  'in-addr'
               5  'arpa'
         'qtype' => 12
   'replyfrom' => '127.0.0.1'
   'replysize' => 80
   'status' => 33152
   'xedns' => Net::DNS::RR::OPT=HASH(0x560a2c650a50)
      'owner' => Net::DNS::DomainName1035=HASH(0x560a2c4c81c0)
         'label' => ARRAY(0x560a2c4c8160)
              empty array
      'type' => 41

As you might imagine, I look for a way to grab answer-ptrdname-label. I have tried:

@$obj{answer)

which at least gives me a part of the object. The same as the method $obj->answer(). But then I am stuck! Help appreciated!

[haj]

The best way to drill that down is to follow the classes of the objects.

1. A Net::DNS::Packet object has the object method answer (You've already figured that out).
2. According to the docs, that answer is a list of Net::DNS::RR objects. These have a type method, which will provide you with 'PTR' (I'm assuming that from your dump).
3. Finally, Net::DNS::RR::PTR objects have a method ptrdname, which provides you with a the string '20.bl.bot.semrush.com'. You get the same result from calling $answer->rdstring, which works for all types of RR records.

In code:

use 5.020;
my @answers = $obj->answer;
for my $answer (@answers) {
    if ($answer->type eq 'PTR') {
        $ptrdname = $answer->ptrdname;
    }
}
say $ptrdname;

[averlon]

Hi haj, thanks - I will try that way!

Problem is, that I did not understand the docu in the right way that this is a kind of drill down through different objects and methods.

Beside this, this also gives me the array. But your solution is much better!

$obj{answer}->[0]{ptrdname}{label}

[Fletch]

Your approach is breaking encapsulation rather than using the objects returned. The answer method returns an array of Net::DNS::RR::PTR instances; you should call methods on the instances in that arrayref rather than pulling values out directly (e.g $result->answer->[0]->ptrdname->name (untested, but hopefully gives the right direction)).

[1nickt]

Hi, I think you want

my $aref = $obj->answer->[0]->ptrdname->label;

To get the second label:

my $aref = $obj->answer->[0]->ptrdname->label->[1];

Hope this helps!

[kcott]

G'day Kallewirsch,

There are a number of modules that will give you a snapshot of an object. Here's a selection (all of these are configurable; see doco for details):

• Data::Dumper — core
• Data::Dump — CPAN
• Data::Printer — CPAN; coloured output (not shown here)

Here's a quick example of each:

$ perl -E '
    use strict;
    use warnings;

    use Net::DNS::Packet;
    my $obj = Net::DNS::Packet::->new(qw{example.com MX IN});

    say "\n*** Data::Dumper";
    use Data::Dumper;
    print Dumper $obj;

    say "\n*** Data::Dump";
    use Data::Dump;
    dd $obj;

    say "\n*** Data::Printer";
    use Data::Printer;
    p $obj;
'

*** Data::Dumper
$VAR1 = bless( {
                 'status' => 0,
                 'authority' => [],
                 'answer' => [],
                 'additional' => [],
                 'question' => [
                                 bless( {
                                          'qtype' => 15,
                                          'qclass' => 1,
                                          'qname' => bless( {
                                                              'label' 
+=> [
                                                                      
+     'example',
                                                                      
+     'com'
                                                                      
+   ]
                                                            }, 'Net::D
+NS::DomainName1035' )
                                        }, 'Net::DNS::Question' )
                               ]
               }, 'Net::DNS::Packet' );

*** Data::Dump
bless({
  additional => [],
  answer     => [],
  authority  => [],
  question   => [
                  bless({
                    qclass => 1,
                    qname  => bless({ label => ["example", "com"] }, "
+Net::DNS::DomainName1035"),
                    qtype  => 15,
                  }, "Net::DNS::Question"),
                ],
  status     => 0,
}, "Net::DNS::Packet")

*** Data::Printer
Net::DNS::Packet  {
    public methods (38):
        additional, answer, answerfrom, answersize, authority, data, d
+ecode, dump, edns, encode, from, header, HEADER_LENGTH, new, pop, pre
+, prerequisite, print, push, question, reply, sign_sig0, sign_tsig, s
+igrr, size, string, truncate, UDPSZ, unique_push, update, verify, ver
+ifyerr, zone
        Carp:
            carp, confess, croak
        Net::DNS::Parameters:
            dsotypebyname, dsotypebyval
    private methods (1): _section
    internals: {
        additional   [],
        answer       [],
        authority    [],
        question     [
            [0] Net::DNS::Question
        ],
        status       0
    }
}

See also:

• perlreftut - Mark's very short tutorial about references
• perlref - Perl references and nested data structures
• perldsc - Perl Data Structures Cookbook