Problems passing hash reference

baxy77bax has asked for the wisdom of the Perl Monks concerning the following question:

I am having problem understanding why this code is not working:


# my Test package (Test.pm)


package Test;

use strict;
use Data::Dumper;

sub new {
    my ($class) = @_;
    my $self->{_name}   = __PACKAGE__;
    $self->{_suffix} = ".sp";
    bless $self, $class;
}



sub make{

  my ($self,$arg) = @_;

  if (ref $arg eq 'ARRAY'){
    foreach my $t (@{$arg}){
      if (ref $t eq 'HASH'){
        _ss($t)
      };
    }
  }

}

sub _ss {
  my ($self, %arg) = @_;

  print Dumper(\%arg);
}

1;


## and my test scritp(test.pl)

use strict;
use lib "./";
use Test;

my $t = Test->new();

my @a;
my %t = (1 =>"1",
         2 => "2");
push(@a,\%t);


$t->make(\@a);
[download]

When I execute I get

$VAR1 = {};
[download]

Why ?? How to pass a hash ref to _ss()

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Re: Problems passing hash reference by shmem (Chancellor) on Oct 11, 2019 at 16:48 UTC
`sub make{ my ($self,$arg) = @_; if (ref $arg eq 'ARRAY'){ foreach my $t (@{$arg}){ if (ref $t eq 'HASH'){ _ss($t) }; } } } sub _ss { my ($self, %arg) = @_; print Dumper(\%arg); }` [download] You probably mean `$self->_ss($t)` [download] since in `sub _ss()` you are shifting away the first argument into `$self`. What happens next? You assign the arguments to a hash, but in the calling code you just pass a single reference, not a key/value pair. So your hash reference ends up as a stringified key in `%arg` with no value attached. perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'	[reply] [d/l] [select]
Re: Problems passing hash reference by AnomalousMonk (Archbishop) on Oct 11, 2019 at 22:02 UTC
Further to shmem's post: `sub _ss { my ($self, %arg) = @_; print Dumper(\%arg); }` [download] ... so what you probably want is something like: `sub _ss { my ($self, $hashref) = @_; print Dumper($hashref); # do stuff with $hashref }` [download] or maybe: `sub _ss { my ($self, $hashref) = @_; my %hash = %$hashref; print Dumper(\%hash); # do stuff with %hash }` [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: Problems passing hash reference by NetWallah (Canon) on Oct 11, 2019 at 22:03 UTC
In addition to shmemem's "$self->_ss()" call, you need to update the _ss argument to be a scalar, instead of a hash, since you are calling it with a scalar "$t".: `sub _ss { my ($self, $arg) = @_; print Dumper($arg); }` [download] Update: I just noticed that AnomalousMonk's post says essentially the same thing. Actually, shmem points this out in his original post. "From there to here, from here to there, funny things are everywhere." -- Dr. Seuss	[reply] [d/l]
Re: Problems passing hash reference by Anonymous Monk on Oct 12, 2019 at 11:04 UTC
Hi. Test is taken. /Local.*/ is always available	[reply]
Re^2: Problems passing hash reference by daxim (Curate) on Oct 15, 2019 at 09:42 UTC
Considered: [AnomalousMonk]: REAP: Meaningless You need some education, AnomalousMonk. Put away your itching reap finger. The namespace Test is already in use, so one should not use it for examples: `perl -mTest -e'print Test->VERSION' # 1.31` [download] The namespace Local is reserved.	[reply] [d/l]