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

Hey Monks, I am rather new to Perl and I cannot quite get my head around why this code doesn't work: 
    my %p = ( outputdir     => undef,
              rptfmt        => 'html',
              rptname       => undef,
              rptfile       => '',
              title         => undef,
              headers       => [],
              data          => [],
              stdout        => 0,
            );

....
cut
.....

my $rpt = Report->new($p{title}, $p{headers}, $p{data});

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Module 
sub new {
    my ($class,$title,$head,$data,$info) = @_;
    my $self = {}; 
    bless ($self, ref ($class) || $class);

    $title ||= "";
    $head = [] if !$head || ref $head ne 'ARRAY';
    $data = [] if !$data || ref $data ne "ARRAY";
    #$rows = $#{@$data} if $data || ref $data eq "ARRAY" || ref $$data
+[0] ne "ARRAY";

    my ($cols,$rows,@justify) = ($#{@$head},$#{@$data});

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The module fails on the last line shown. The error is: Can't use string ("9") as an ARRAY ref while "strict refs" in use at .//Report.pm line 72. I am following an example I was given so it must be outside the module that is wrong.. Any ideas?

Replies are listed 'Best First'.
Re: Cannot find error : Can't use string ("9") as an ARRAY ref while "strict refs" ...
by Corion (Patriarch) on Mar 12, 2009 at 16:21 UTC

    The error is correct, because this expression: $#{@$head} does not do what you think it should. I assume you want the number of elements in @$head there. If head were an array, your code would look like this:

    sub new {
    ...
    my @head = (1,2,3);
    my $cols = $#head;
    ...
};

    [download]

    This already is wrong, because $#head is the index of the last element, so $cols will be 2, not 3. But to translate the code above, just follow References Quick Reference and write:

    sub new {
    ...
    my $head = [1,2,3];
    my $cols = $#{$head};
    ...
};

    [download]
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Re: Cannot find error : Can't use string ("9") as an ARRAY ref while "strict refs" ...
by dreadpiratepeter (Priest) on Mar 12, 2009 at 16:24 UTC
    the $#{} construct is a deref and expects a reference. you passed it @$head, which is an array, not an arrayref. the array in scalar context gives the number of elements in it. since the $#{} construct needs a reference, which is a scalar, you are passing it 9


    -pete
    "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."
[reply]
      spot on guys, cheers!
[reply]

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