Perl WWW:Mechanize Accessing data in a hash reference - perl

Question

I have a question I'm hoping you could help with?
This is the last part I need help with in understanding hash references
Code:
my $content_lengths; # this is at the top
foreach my $url ( # ... more stuff
# compare
if ( $mech->response->header('Content-Length') != $content_length ) {
print "$child_url: different content length: $content_length vs "
. $mech->response->header('Content-Length') . "!\n";
# store the urls that are found to have different content
# lengths to the base url only if the same url has not already been stored
$content_lengths->{$url}->{'different'}->{$child_url} = $mech->response->header('Content-Length');
} elsif ( $mech->response->header('Content-Length') == $content_length ) {
print "Content lengths are the same\n";
# store the urls that are found to have the same content length as the base
# url only if the same url has not already been stored
$content_lengths->{$url}->{'equal'}->{$child_url} = $mech->response->header('Content-Length');
}
What it looked like using Data::Dumper
$VAR1 = {
'http://www.superuser.com/' => {
'difference' => {
'http://www.superuser.com/questions' => '10735',
'http://www.superuser.com/faq' => '13095'
},
'equal' => {
'http://www.superuser.com/ ' => '20892'
}
},
'http://www.stackoverflow.com/' => {
'difference' => {
'http://www.stackoverflow.com/faq' => '13015',
'http://www.stackoverflow.com/questions' => '10506'
},
'equal' => {
'http://www.stackoverflow.com/ ' => '33362'
}
}
};
What I need help with:
I need help understanding the various ways of accessing the different parts in the hash reference and using them to do things, such as print them.
So for example how do I print all the $url from the hash reference (i.e from Data::Dumper that will be http://www.superuser.com/ and http://www.stackoverflow.com/)
and how do I print all the $child_url or a particular one/subset from $child_url and so on?
Your help with this is much appreciated,
thanks a lot

Answer 1

You can navigate your hashref thusly:
$hashref->{key1}{key2}{keyN};
For example, if you want the superuser equal branch:
my $urlArrayref = $hashref->{'http://www.superuser.com/'}{'equal'};
More to the point, to print the urls (first level key) of the hashref, you would do:
foreach my $key ( keys( %{$hashref} ) ) {
print( "key is '$key'\n" );
}
Then if you wanted the second level keys:
foreach my $firstLevelKey ( keys( %{$hashref} ) ) {
print( "first level key is '$firstLevelKey'\n" );
foreach my $secondLevelKey ( keys( %{$hashref->{$firstLevelKey}} ) ) {
print( "\tfirst level key is '$secondLevelKey'\n" );
}
}
And so forth...
----- EDIT -----
This is working sample code from your example above:
#!/usr/bin/perl
use strict;
use warnings;
my $content_lengths = {
'http://www.superuser.com/' => {
'difference' => {
'http://www.superuser.com/questions' => '10735',
'http://www.superuser.com/faq' => '13095'
},
'equal' => {
'http://www.superuser.com/ ' => '20892'
}
},
'http://www.stackoverflow.com/' => {
'difference' => {
'http://www.stackoverflow.com/faq' => '13015',
'http://www.stackoverflow.com/questions' => '10506'
},
'equal' => {
'http://www.stackoverflow.com/ ' => '33362'
}
}
};
foreach my $key1 ( keys( %{$content_lengths} ) ) {
print( "$key1\n" );
foreach my $key2 ( keys( %{$content_lengths->{$key1}} ) ) {
print( "\t$key2\n" );
foreach my $key3 ( keys( %{$content_lengths->{$key1}{$key2}} ) ) {
print( "\t\t$key3\n" );
}
}
}
Which results in this output:
http://www.superuser.com/
difference
http://www.superuser.com/questions
http://www.superuser.com/faq
equal
http://www.superuser.com/
http://www.stackoverflow.com/
difference
http://www.stackoverflow.com/faq
http://www.stackoverflow.com/questions
equal
http://www.stackoverflow.com/