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Does inner hash/key exist?

by blink (Scribe)
on May 31, 2003 at 13:47 UTC ( [id://262065]=perlquestion: print w/replies, xml ) Need Help??

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

Given the following code, how could I effectively test for the existance of (@{$failed{$client}}, $sid) before populating it? I'm not sure how to use 'exist' in the context of a nested data structure. 
foreach my $key (sort keys %jobs)
{

    my $job    = $jobs{$key}->{jobid};
    my $status = $jobs{$key}->{status};
    my $client = $jobs{$key}->{client};
    my $class  = $jobs{$key}->{class};
    my $files  = $jobs{$key}->{files};

    if ($status gt 0 && $status ne 150)
    {
        my ($host, $sid, $type) = split ('_', $class);
        if ($type =~ /hot|cold/)
        {
            push (@{$failed{$client}}, $sid);
        }
        else
        {
            push (@{$failed{$client}}, $files);

        }
    }
}

[download]

Replies are listed 'Best First'.
Re: Does inner hash/key exist?
by pfaut (Priest) on May 31, 2003 at 13:55 UTC

    grep?

    push @{$failed{$client}}, $sid unless grep $_ eq $sid, @{$failed{$clie
+nt}};

    [download]
    90% of every Perl application is already written. ⇒
    dragonchild
[reply]
[d/l]
      Perfect! Thanks!
[reply]
Re: Does inner hash/key exist?
by Aristotle (Chancellor) on May 31, 2003 at 14:04 UTC
    pfaut answered your question, I'd just like to add some minor advice: you can remove redundancy in your assignments block by using a hash slice. 
    my ($job, $status, $client, $class, $files)
    = @{$jobs{$key}}{qw(jobid status client class files)};

    [download]

    Makeshifts last the longest.

[reply]
[d/l]
Re: Does inner hash/key exist?
by runrig (Abbot) on May 31, 2003 at 15:05 UTC
    pfaut already answered your question, but when you have to grep through arrays to determine existance, you almost always should be using a hash and the exists function. Even if you need to keep them in the order that they were found, you can use your array in conjunction with a separate hash (or hash of hashes in your case):
    push {@{$failed{$client}}, $sid unless exists $fail{$client}{$sid};
$fail{$client}{$sid} = undef;

    [download]
    Or just do the second statement if you don't need to keep the keys in order, then it doesn't matter if it exists already.
[reply]
[d/l]

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