Get just the unique value

[Anonymous Monk]

Hi there Monks!

I need to get only the unique value from this anonymous array of hashes, but I just don’t understand why this code can't?

#/usr/bin/perl

use strict; 
use Data::Dumper;

my $data = [
   {
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },
   {
     'name' => 'Documents',
     'reference' => '100       ',
     'type' => 'Paper'
   },
   {
     'name' => 'Money',
     'reference' => '340       ',
     'type' => 'Plastic'
   },   {
     'name' => 'Money',
     'reference' => '340       ',
     'type' => 'Plastic'
   },   {
     'name' => 'Money',
     'reference' => '340       ',
     'type' => 'Plastic'
   },   {
     'name' => 'Money',
     'reference' => '340       ',
     'type' => 'Plastic'
   },
   {
     'name' => 'State',
     'reference' => '40        ',
     'type' => 'Cotton'
   },
   {
     'name' => 'State',
     'reference' => '40        ',
     'type' => 'Cotton'
   },
   {
     'name' => 'State',
     'reference' => '40        ',
     'type' => 'Cotton'
   },
   {
     'name' => 'Slice',
     'reference' => '30        ',
     'type' => 'Cotton'
   },
   {
     'name' => 'Part',
     'reference' => '45        ',
     'type' => 'Cotton'
   },
{
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },
{
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },
{
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },
{
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },
{
     'name' => 'Discount',
     'reference' => '100       ',
     'type' => 'Paper'
   },

];

my $res;

 for my $entry (@$data) {
     
     #$entry->{type} = [] unless exists $entry->{type};
     
     push @$res, $entry->{type} unless $entry;
   
 }

print Dumper @$res;

Thanks for looking!

[CountOrlok]

Use a hash instead:

my %res = ();

for my $entry (@$data) {
     $res{$entry->{type}} = 1;
}
print join(',', sort(keys(%res)))."\n";

[hdb]

Use a hash and build keys from the whole entry:

my %res;

for my $entry (@$data) {
  $res{join "|", sort %{$entry}} = $entry; 
}    

@$data = values %res;

print Dumper $data;

UPDATE: Added a "sort" to become independent from order within the hash.

[Anonymous Monk]

It still doesnt work, I am still getting duplicated "type":

$VAR1 = [
          {
            'reference' => '100       ',
            'name' => 'Discount',
            'type' => 'Paper'
          },
          {
            'reference' => '30        ',
            'name' => 'Slice',
            'type' => 'Cotton'
          },
          {
            'reference' => '340       ',
            'name' => 'Money',
            'type' => 'Plastic'
          },
          {
            'reference' => '100       ',
            'name' => 'Documents',
            'type' => 'Paper'
          },
          {
            'reference' => '45        ',
            'name' => 'Part',
            'type' => 'Cotton'
          },
          {
            'reference' => '40        ',
            'name' => 'State',
            'type' => 'Cotton'
          }
        ];

[hdb]

Well, these are the distinct records from your original array of hashes. You did not specify which value is to be unique. I would think that you should now be able from the answers here and the answers from your post yesterday: Accessing this array ref. to conclude whatever you wanted to achieve.

[CountOrlok]

It isn't clear what you want for output. You want to remove entries in the original data where type is duplicated, it seems, but how do you want to handle the case where reference or name is different? Which entry in the arrayref do you want to choose?

[jaredor]

use Modern::Perl;
use List::MoreUtils qw(uniq);
use Data::Dump qw(pp);
my $data = { ... your array of hashes here ... };
my @names = uniq map { $_->{'type'} } @$data;
pp \@names;

[NetWallah]

You could do it without naming a temporary hash - I'm not recommending you do this, but it was fun writing:

print qq|$_ | for sort keys %{{ +map {$_->{type} => undef} @$data }};

Prints:
Cotton Paper Plastic