Returning and passing references to hashes

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

I am returning a reference to an array a scalar and 2 references to hashes
I then pass these values to different subroutines.
How do I loop through the values of the hashes.
below is the code that passes returns the values

my($dbh) = @_;
    my @datamodels;
    my %filenames;
    my %dbids;
    my $sql = "select DATAMODEL_CD, DB_ID, FILENAME from PRDRELEASE wh
+ere RELEASE_FG = 1";
    my $sth = $$dbh->prepare($sql)
           or $app->error($FATAL, "Can't do SQL statement [ $sql ] :: 
+$DBI::errstr");
    $sth->execute();

    while (my @values = $sth->fetchrow_array()){
    push (@datamodels, $values[0]);
    $dbids{$values[0]} = $values[1];
    $filenames{$values[0]} = $values[2];
    }#end while loop

    printf("@datamodels\n");
    my $numelements = @datamodels;
    return (\@datamodels, $numelements, \%dbids, \%filenames);
[download]

This is the code recieving the the values from the above code

my ($datamodels, $numelements, $dbids, $filenames) = get_data(\$dbh);
[download]

Now I pass filenames to a different subroutine.
create_file(\$dbh, $datamodels, $date, $numelements, $filenames);

How do I call the appropriate value within the calling subroutine?
This is what I have tried.

my ($dbh, $datamodel, $date, $numelements, $filenames) = @_; 
my $file = "$filenames{$datamodel->[$count]}"
print "$file\n";
[download]

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Re: Returning and passing references to hashes by ikegami (Patriarch) on Jan 04, 2006 at 18:48 UTC
You're treating "filenames" as a hash `$filenames{...}` instead of a reference to a hash `$filenames->{...}` or `${$filenames}{...}` In other words, `my $file = "$filenames{$datamodel->[$count]}";` should be `my $file = $filenames->{$datamodels->[$count]};` (What's with the quotes?) Update: ... except that $count is undefined. Maybe you want `foreach my $datamodel (@$datamodels) { my $file = $filenames->{$datamodel}; print "$file\n"; }` [download] You could also do away with $datamodels entirely, but the order of the output would be random. `foreach my $datamodel (keys %$filenames) { my $file = $filenames->{$datamodel}; print "$file\n"; }` [download] I'd get rid of $numelements. There's no use for it. Update: Some PerlMonks references on references: Dereferencing Syntax References Quick Reference References Tutorial	[reply] [d/l] [select]
Re^2: Returning and passing references to hashes by mnlight (Scribe) on Jan 04, 2006 at 19:59 UTC
`my $file = $filenames->{$datamodel};` this will work. the quotes were just a mistake. Now that I can reference it this way I will get rid of numelements. I will keep those references in my favorites thank you.	[reply] [d/l]
Re: Returning and passing references to hashes by Roy Johnson (Monsignor) on Jan 04, 2006 at 18:37 UTC
See perldoc perlreftut about using references. If you have hashrefs in scalar variables (as you do, e.g., $dbids), you can loop through the values like so: `for my $val (values %$dbids) { # Do something with a value...` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l]