Iterating through a HoHoH ... does a particular sub-hash exist?

[jedikaiti]

I have a hash, much like the one below:

%cmdData = (
     'command_1' => {
          'subfields' => [],
          'description' => 'descriptive text',
          'safety' => 'SAFE'
                    },
     'command_2' => {
          'subfields' => [
               {
                  '_size' => 32,
                   'state_conversions' => [],
                   'subfield_name' => 'sub_1',
                   '_fsw_type' => 'UINT32',
               },
               {
                  '_size' => 32,
                   'state_conversions' => [],
                   'subfield_name' => 'sub_2',
                   '_fsw_type' => 'UINT32',
               },
                          ],
          'description' => 'descriptive text',
          'safety' => 'SAFE',
                    }
)

What I want to do is to loop through each command (key) in the hash, and do X if it has one or more subfields, and Y if it has 0 subfields. So I have a foreach loop in my code (below), with an if/else statement.

Problem is, I can't get the if/else conditions right. I have tried it as below, and I have tried if (not defined $cmdData->{$cmd}{subfields}). In both cases, it prints all the command names, followed by "defined".

#!/usr/bin/perl -w
use strict;
use warnings;
use Storable;

my %info;
my $cmdData = retrieve('file.pm')

foreach my $cmd ( sort { $cmdData->{$a}{pkt_target} cmp $cmdData->{$b}
+{pkt_target} || $a cmp $b } keys %{$cmdData}) {
    print "$cmd   ";

    if ($cmdData->{$cmd}{subfields} eq "") {
        print "undef\n";
    } else {
        print "defined\n";
    }
};

Yes, I can change the hash I'm working with - sort of. I have a preprocessing script that is compiling a whole mess of hashes of the same format into one big one in a file (so it's easier to iterate through later). I can change that script to output something nicer, but I still need to know how to tell if there are subfields or not (this is how they appear in the original hashes I'm pulling from) so I can fix them.

Thanks a million, Monks!

[ikegami]

$cmdData->{command_1}{subfields} is defined. It's an array reference.
$cmdData->{command_2}{subfields} is defined. It's an array reference.

Sounds like you want to check the number of elements in the referenced array. That would be

@{ $cmdData->{$cmd}{subfields} }

in scalar context.

[CountZero]

Are you using the strictures, jedikaiti?

If you did, you would have seen that

$cmdData->{$cmd}{subfields}

gives you an error, unless you have elsewhere declared $cmdData.

$cmdData->... contains a scalar reference and has nothing to do with your hash %cmdData. You probably meant something like $cmdData{'command_2'}->{subfields}.

Update: Forget what I wrote above. I somehow totally missed the code in your node. Thanks almut for pointing that out to me.

[almut]

I guess the retrieve in my $cmdData = retrieve('file.pm') would return a reference to the hash in question, so things should be fine.