array of hashes

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monk,

i want to fetch the elements of array, which contain hashes, using reference. i have written the following code but there are errors. Would you help me with my code.

#!/usr/bin/perl -w

        use strict;

        my @arr;
        my %one;
        my %sec;
        my %thr;

         %one = { 1    => 'mili',
                       2  => 'brown',
                          3 => 'kalu'
                     };
         %sec = { 'age'    => 23,
                       'eyes'   => 'hazel',
                            'weight' => 128
                     };
         %thr = { 'name'    => 'deep',
                       'roll'   => 02,
                          'class' => 'BI'
                     };

        my $one = \%one;
        my $sec = \%sec;
        my $thr = \%thr;

        @arr = ($one, $sec, $thr);
        my $ref = \@arr;

        for (my $i = 0; $i < 3; $i++) {
                my $a = $$ref[$i];
                print "$a";
                foreach my $x (keys %{$a}) {
                        print $x;
                }
        }

exit 0;
[download]

Thank You

Comment on array of hashes Download Code

Replies are listed 'Best First'.
Re: array of hashes by bart (Canon) on Feb 10, 2011 at 12:37 UTC
`%one = { 1 => 'mili', 2 => 'brown', 3 => 'kalu' };` Wrong. You should decide on whether you want to use a hash, in which case you must use normal parens; or a hash ref, in which case you can the curly braces. Thus, choose between: `%one = ( 1 => 'mili', 2 => 'brown', 3 => 'kalu' );` [download] and `$one = { 1 => 'mili', 2 => 'brown', 3 => 'kalu' };` [download] Note that %one and $one are not the same variable, and you use them differently. So you have to adapt the rest of your code to this choice. I see you've made this same mistake several times in your code.	[reply] [d/l] [select]
Re^2: array of hashes by AnomalousMonk (Archbishop) on Feb 10, 2011 at 21:55 UTC
It would also be wise for a novice Anonymonk to `use` diagnostics`;` in addition to both strict and warnings in his or her code: >perl -wMstrict -le "use diagnostics; ;; my %hash = { foo => 'bar' }; " Reference found where even-sized list expected at -e line 1 (#1) (W misc) You gave a single reference where Perl was expecting a list with an even number of elements (for assignment to a hash). This usually means that you used the anon hash constructor when you meant to use parens. In any case, a hash requires key/value pairs. %hash = { one => 1, two => 2, }; # WRONG %hash = [ qw/ an anon array / ]; # WRONG %hash = ( one => 1, two => 2, ); # right %hash = qw( one 1 two 2 ); # also fine [download]	[reply] [d/l] [select]
Re: array of hashes by moritz (Cardinal) on Feb 10, 2011 at 10:57 UTC
If you put your code in `<code>...</code>` tags, and tell us what errors you get, maybe we can help you. See also: How (Not) To Ask A Question, Writeup Formatting Tips Perl 6 - second systems done right	[reply] [d/l]
Re: array of hashes by hsinclai (Deacon) on Feb 10, 2011 at 16:59 UTC
`#!/usr/bin/perl -w use strict; my $one = { 1 => 'mili', 2 => 'brown', 3 => 'kalu' }; my $sec = { 'age' => 23, 'eyes' => 'hazel', 'weight' => 128 }; my $thr = { 'name' => 'deep', 'roll' => 02, 'class' => 'BI' }; my @arr = ($one, $sec, $thr); my $ref = \@arr; for (my $i = 0; $i < 3; $i++) { while ( my($k,$v) = each %{$$ref[$i]} ) { print " $k " . '-> ' . $v . $/; } }` [download] There must be a nicer way to lay out the dereferencing, someone anyone?	[reply] [d/l]
Re^2: array of hashes by AnomalousMonk (Archbishop) on Feb 10, 2011 at 21:41 UTC
`>perl -wMstrict -le "# as before... ;; my $arrayref = [ $one, $sec, $thr, ]; ;; for my $hashref (@$arrayref) { while (my ($k, $v) = each %$hashref) { print qq{ '$k' -> '$v'}; } } " '1' -> 'mili' '3' -> 'kalu' '2' -> 'brown' 'weight' -> '128' 'eyes' -> 'hazel' 'age' -> '23' 'name' -> 'deep' 'class' -> 'BI' 'roll' -> '2'` [download]	[reply] [d/l]