RE: Hash of Hashes - Error

[anand.jawaji]

Thanks a lot for the suggestions and solution.

Regards,
Anand

-----Original Message-----
From: Shlomi Fish [mailto:shlo...@shlomifish.org] 
Sent: Tuesday, August 23, 2011 5:09 PM
To: Jawaji, Anand
Cc: beginners@perl.org
Subject: Re: Hash of Hashes - Error

Hi Anand,

On Tue, 23 Aug 2011 05:57:02 -0400
<anand.jaw...@emc.com> wrote:

> Hi All,
> 
> I am working on the below code to traverse through a hash, but it throws an
> error which states "Can't coerce array into hash at temp.pl line 6."
> 

First of all, let me note that the indentation on that code is inconsistent and
erratic. But I was able to fix it by importing it into Vim and using the
"=" key (= "format") and some manual tweaks. Here is the correct version:

[CODE]
#!/usr/bin/perl

use strict;
use warnings;

sub hash_walk {
    my $self = shift;

    my ($hash, $key_list, $callback) = @_;

    while (my ($k, $v) = each (%$hash)) {
        push @$key_list, $k;

        if (ref($v) eq 'HASH') {
            $self->hash_walk($v, $key_list, $callback);
        }
        else {
            $callback->($k, \$v, $key_list);
        }

        pop @$key_list;

        $hash->{$k} = $v;
    }
}

my %data = (
    a => {
        ab => 1,
        ac => 2,
        ad => {
            ada => 3,
            adb => 4,
            adc => {
                adca => 5,
                adcb => 6,
            },
        },
    },
    b => 7,
    c => {
        ca => 8,
        cb => {
            cba => 9,
            cbb => 10,
        },
    },
);

hash_walk(\%data, [], \&replace_all_val_strings);

sub replace_all_val_strings {
    my ($k, $v, $key_list) = @_;
    printf "k = %-8s  v = %-4s  key_list = [%s]\n", $k, $$v, "@$key_list";
    $$v =~ s/oldstr/newstr/;
    printf "k = %-8s  v = %-4s  key_list = [%s]\n", $k, $$v, "@$key_list";
}
[/CODE]

Now after I did that, I used the perl debugger ("perl -d") to debug the code
(see http://perl-begin.org/topics/debugging/ ), and realised that the problem
was that hash_walk expects 4 arguments (including "$self" which is the object
handle), while it is only given 3 in the initial call, which fails. 

Do you need the "$self" or is there a good reason for that? If you do, read the
Object Oriented programming resources at
http://perl-begin.org/topics/object-oriented/ , because otherwise it's just
cargo-cult programming.

Also see:

http://perl-begin.org/tutorials/bad-elements/

Regards,

        Shlomi Fish

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