reaper9187 has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone ..
I'm working on a problem.. Jus need some help with the following code: 
use Data::Dumper;
use strict;

our (@a,$c,$key,$bar);

 #!/usr/bin/perl
  use strict;
  use warnings;

use Data::Dumper;
  use Tk;
  use Tk::Chart::Lines;

  my $mw = MainWindow->new(
    -title      => 'Tk::Chart::Lines example',
    -background => 'white',
  );
  my $chart = $mw->Lines(
    -title  => 'My graph title',
    -xlabel => 'X Label',
    -ylabel => 'Y Label',
  )->pack(qw / -fill both -expand 1 /);

@a = qw/Mon Tue Wed Thurs/;

foreach $key(@a)
{
    
push(@{${$key}[0]},1,33);    
push(@{${$key}[0]},22,11);    
push(@{${$key}[1]},2,5);    
push(@{${$key}[2]},3,4);

}
  
$c ="Mon";

  # Add a legend to the graph
  my @legends = ( 'legend 1', 'legend 2', 'legend 3' );
  $chart->set_legend(
    -title       => 'Title legend',
    -data        => \@legends,
    -titlecolors => 'blue',
  );

  # Add help identification
  $chart->set_balloon();
print Dumper(@$c);

  # Create the graph
  $chart->plot( @$c );
  
  

  MainLoop();

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I get the error.. "Cant use string "Mon" as array ref while strict refs in use ... "

How do i solve this issue .. Please help ..!!!

Replies are listed 'Best First'.
Re: Cant use string(_) as array ref..!!
by choroba (Cardinal) on Jan 24, 2013 at 09:17 UTC
    Let's analyze it. @a is an array of strings. Next, you iterate over it with
    foreach $key (@a)

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    So, $key is a string, "Mon" in the first iteration. Then, you use the expression
    ${$key}[0]

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    It tries to dereference $key as an array reference, but it is not: it is a scalar string. Hence the error.
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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Re: Cant use string(_) as array ref..!!
by Anonymous Monk on Jan 24, 2013 at 09:14 UTC
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Re: Cant use string(_) as array ref..!!
by thundergnat (Deacon) on Jan 24, 2013 at 14:33 UTC

    Update: changed 'indirect' to 'symbolic' as that is what I meant, but blanked out on while I was composing my post.

    First off, Kudos for using the strict and warnings pragmas. They will really help you catch typos and silly errors in your script.

    push(@{${$key}[0]},1,33);    
push(@{${$key}[0]},22,11);    
push(@{${$key}[1]},2,5);    
push(@{${$key}[2]},3,4);

    [download]

    Ok you are trying to use indirect symbolic referencing to autovivify your hashes and that is not allowed under the strict pragma. You would probably be better off just predeclaring a single hash and use the day names as keys. Did you really want a 4 element array at index 0 and 2 element arrays elsewhere? Tk::Chart::Lines is going to complain about that. Anyway see if this clears anything up for you.

    #!/usr/bin/perl
use strict;
use warnings;

use Data::Dumper;
use Tk;
use Tk::Chart::Lines;

my $mw = MainWindow->new(
    -title      => 'Tk::Chart::Lines example',
    -background => 'white',
);

my $chart = $mw->Lines(
    -title  => 'My graph title',
    -xlabel => 'X Label',
    -ylabel => 'Y Label',
)->pack(qw / -fill both -expand 1 /);

my @a = qw/Mon Tue Wed Thurs/;

my %days;

foreach my $key (@a)
{
    push @{$days{$key}}, [1, 33];    
    push @{$days{$key}}, [22, 11];    
    push @{$days{$key}}, [2, 5];    
    push @{$days{$key}}, [3, 4];
}
  
my $c ='Mon';

# Add a legend to the graph
my @legends = ( 'legend 1', 'legend 2', 'legend 3' );
$chart->set_legend(
    -title       => 'Title legend',
    -data        => \@legends,
    -titlecolors => 'blue',
);

# Add help identification
$chart->set_balloon();
#print Dumper \$days{$c};

# Create the graph
$chart->plot( $days{$c} );

MainLoop;

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Re: Cant use string(_) as array ref..!!
by reaper9187 (Scribe) on Jan 24, 2013 at 09:22 UTC
    Can you please suggest a way to remove this issue ????
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      Just for clarification can you tell me what you are doing here ? push(@{${$key}[0]},1,33);

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