CODEWITHSUNDEEP
xmlarraysperlhash
Jeff
Jeff

Reputation: 4433

Accessing each hash member of array -- Perl

I am trying to access each member of a hash I have stored in an array in Perl. I have already seen Looping through an array of hashes in Perl, and I need a better way to access them. My end result will be splitting the taking each item (hash) in an array, storing the keys of that hash in a new array, storing the values of the array in a different array.

Edit: I changed they way my hashes get their data to reflect my code better. I didn't think it mattered, but it does.

XML SOURCE:

<XML>
    <computer>
        <network>
            <interface1>
                <name>eht0</name>
                <ip>182.32.14.52</ip>
            </interface1>
            <interface2>
                <name>eth2</name>
                <ip>123.234.13.41</ip>
            </interface2>
        </network>
    </computer>
</xml>

PERL CODE:

my %interfaceHash;
for(my $i=0; $i < $numOfInterfaces; $i++ ){
    my $interfaceNodes = $xmldoc->findnodes('//computer/network/interface'.($i+1).'/*');
    foreach my $inode ($interfaceNodes->get_nodelist){
        my $inetValue = $inode->textContent();
        if ($inetValue){
            my $inetField = $inode->localname;
            push (@net_int_fields, $inetField);
            push (@net_int_values, $inetValue);
        }
    }
    for(my $i =0; $i< ($#net_int_fields); $i++){
        $net_int_hash{"$net_int_fields[$i]"} = "$net_int_values[$i]";
    }
    push (@networkInterfaces, \%net_int_hash); #stores 
}

Now, if I try to access the array, it wipes out what was stored in the hash.

Upvotes: 0

Views: 184

Answers (3)

DVK
DVK

Reputation: 129559

Your problem is that a hash can NOT be a member of an array. Only a scalar can.

What you need in an array is not a hash, but a scalar reference to the hash:

push @networkInterfaces \%interface1; # \ is a reference taking operator

Then, to access an individual element of that hashref, you do

$networkInterfaces[0]->{iFaceName}; # "->{}" accesses a value of a hash reference

To access a whole hash (e.g. to get its keys), dereference using %{ hashref } syntax:

foreach my $key ( keys %{ $networkInterfaces[0] } ) {

Upvotes: 1

choroba
choroba

Reputation: 242423

To build complex data structures in Perl, start with reading perldsc - Perl Data Structures Cookbook.

#!/usr/bin/perl
use warnings;
use strict;

my %interface1 = (iFaceName => 'eth0',
                  ipAddr    => '192.168.0.43',
                 );
my %interface2 = (iFaceName => 'eth1',
                  ipAddr    => '192.168.10.64',
                 );
my @networkInterfaces;
my @iFaceKeys;
my @iFaceVals;
push @networkInterfaces, \%interface1; # Note the backslash!
push @networkInterfaces, \%interface2;

for my $iFace (@networkInterfaces) {
    push @iFaceKeys, keys   %$iFace;
    push @iFaceVals, values %$iFace;
}

Upvotes: 3

Kris
Kris

Reputation: 193

One good way to do this is to create an array of hash refs.

%first_hash = (a => 1, b => 2);
%second_hash = (a => 3, b => 4);

@array_of_hash_refs = ( \%first_hash, \%second_hash );

foreach $hash_ref (@array_of_hash_refs)
{
        print "a = ", $hash->{a}, "\n";
        print "b = ", $hash->{b}, "\n";
}

Keep in mind that perl has different syntax to access hash data depending on whether you are working with a hash object or a reference to a hash object.

$hash_ref->{key}
$hash{key}

Upvotes: 0

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