in reply to Re: dereferencing syntax Re: Getting keys/values from a referenced hash
in thread Getting keys/values from a referenced hash

Hi again Misha, here's my $.2,

Well, this line (which I think is equivalent) works ok: 

perl -e 'my $nested = { key_to_hash => {data => "here"}}; print %{$nes
+ted->{key_to_has
h}};'

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The error message simply means that $hashref is undefined, i.e. the scalar called 'hashref' contains no value. So this means that there is a problem with $nested->{key_to_hash} - maybe the key key_to_hash doesn't exist, or the value is undefined. Maybe $nested is pointing to the wrong hash.

An easy way to see what's gone wrong is to use the module Data::Dumper - which is standard, so you probably have it. Do this:

use Data::Dumper;
print Dumper($nested);

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and you'll see the contents of the hash referred to by $nested.

If you can't see what's up with it, post the code where you set up $nested.

Have a nice day and thanks for the tips yesterday!
That's ok, you too.

andy.

Replies are listed 'Best First'.
Re: dereferencing stuff
by professa (Beadle) on Nov 28, 2001 at 17:55 UTC
    Hi Andy!

    I found out now (using Dumper-mod) that my reference to the nested hash is undefined (but only when I use use strict;)
    When I don't use strict the reference ($results) holds all the data I want and is dumped correctly. Here's the way I get the nested hash from a file (the only possibility I have):

    my $filename = $ARGV[0];
open (_filehandle_, "<$filename") or die "Meeeeep! $filename does not 
+exist!\n";
my @file = <_filehandle_>;
close (_filehandle_);
my $line = join "", @file;
my $results = eval ($line);
print '$results: '.Dumper($results);
my $colpattern = $results->{"col_pattern"};

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    That's pretty straight and ineffective code, but I better first try how things work and squeeze it up later then. ;-)
    The fact that $results is undef tells me sth. goes wrong with eval().
    Can it be that the use strict-statement affects or somehow impairs the evaluation of the file's contents (which is in $line now)?

    Greetz, Micha

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[d/l]
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      Looks like the code you are evaling isn't strict compatible. You should check the value of $@ right after your eval. For instance, try this script with and without strict: 
      #!/usr/bin/perl -wT
use strict;

my $c;
my $code = '$global = 10; $c = 6';
eval $code;
die $@ if $@;
print "\$c = $c\n";

__END__

=head1 OUTPUT with strict
Global symbol "$global" requires explicit package name at (eval 1) lin
+e 1.

=head2 OUTPUT w/o strict
$c = 6

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      Also, your slurp-and-eval would be cleaner as a require or a do instead.

      -Blake

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[d/l]
        Seems to be the code from that file to be the error:

        Global symbol "$res_g2" requires explicit package name at (eval 2) line 1.

        Var $res_g2 holds the nested array I need to evaluate. Since I have no influence on the code written to the file I think I have to live without strict for that part.
        Thanks a lot!

        Micha

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[d/l]
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Re: Re: Re: dereferencing syntax Re: Getting keys/values from a referenced hash
by professa (Beadle) on Nov 28, 2001 at 18:04 UTC
    (whoops! I think I started a new thread accidentally by changing the subject line...)

    Hi Andy!

    I found out now (using Dumper-mod) that my reference to the nested hash is undefined (but only when I use use strict;)
    When I don't use strict the reference ($results) holds all the data I want and is dumped correctly. Here's the way I get the nested hash from a file (the only possibility I have):

    my $filename = $ARGV[0];
open (_filehandle_, "<$filename") or die "Meeeeep! $filename does not 
+exist!\n";
my @file = <_filehandle_>;
close (_filehandle_);
my $line = join "", @file;
my $results = eval ($line);
print '$results: '.Dumper($results);
my $colpattern = $results->{"col_pattern"};

    [download]

    That's pretty straight and ineffective code, but I better first try how things work and squeeze it up later then. ;-)
    As output from ::Dumper I get: $results: $VAR1 = undef;
    The fact that $results is undef tells me sth. goes wrong with eval().
    Can it be that the use strict-statement affects or somehow impairs the evaluation of the file's contents (which is in $line now)?

    Greetz, Micha

[reply]
[d/l]
[select]
      Yep, first think, then post. Stupid me.
      The posts just didn't show up coz I restricted the note depth...I noticed now, sorry for that!

      Micha

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