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

Hi

I'm using the following code to process lines in the $discovered array, and create a number of hashed pairs in the same array row. The code works well. 

until ($discovered[$i] eq ""){
 ($key, $value) = split /:\s*/, $discovered[$i];
 $arrayAoH[$j]{$key} = $value;
 $i++;
}

[download]

But, when I enabled 'use strict' in my code, I get the following error when the line containing '$arrayAoH[$j]{$key} = $value;' is executed:

"Can't use string ("") as a HASH ref while "strict refs" in use at xxx.pl"

I've pored over the examples in 'Programming Perl', and have Google'd a bit. But I just don't understand why that line is wrong, and what I should do to fix it.

I tried using the following line in place of the offending line: 

 $arrayAoH[$j] = { $key => $value };

[download]

but it creates an array row with only a single has (whatever the last has processed was).

Thoughts, please!

Thanks tl

20050623 Edit by ysth: code tags

Replies are listed 'Best First'.
Re: Array of hashes reference problem
by tlm (Prior) on Jun 22, 2005 at 17:34 UTC

    Where is $j defined? What's it's value? It looks like $arrayAoH[$j] contains an empty string, not a hash ref.

    the lowliest monk

[reply]
      Sorry, here's the whole code segment:

         our @arrayAoH = "";
    my $i = 0; # i holds the line number of the input (@discovered) ar
+ray.
    my $j = 0; # j holds the number of the table row.
   my $key;
   my $value;
# $# returns the subscript of the last element in the array.
    until ($i eq $#discovered){
        if ($discovered[$i] =~ m/Item Number:/){
# parse this line containing labels and values until a blank line is f
+ound
            until ($discovered[$i] eq ""){
                ($key, $value) = split /:\s*/, $discovered[$i];
##            $arrayAoH[$j] = { $key => $value };
                $arrayAoH[$j]{$key} = $value;
                $i++;
            }
# If the selected item shouldn't be processed, remove this array row.
            if (($arrayAoH[$j]{"Model Number"} !~ m/^Foo/)){
                splice (@arrayAoH, $j, 1);
            }
            else {
            $j++;
            }
        }
        else {
        $i++;}
    }

      [download]

      20050623 Edit by ysth: code tags

[reply]
[d/l]
        here's the whole code segment
        I doubt that. This code won't parse.

        When using strict, you have to declare $arrayAoH first. Besides,

        $arrayAoH$j{$key} = $value;

        [download]
        should read:
        $arrayAoH[$j]{$key} = $value;

        [download]
        and
        if (($arrayAoH$j{"Model Number"} !~ m/^Foo/)){

        [download]
        should be
        if (($arrayAoH[$j]{"Model Number"} !~ m/^Foo/)){

        [download]
        Please post actual code...

        Paul

[reply]
[d/l]
[select]
        The eventual solution found by sapnac got buried below so I'll re-mention it here with an explanation. The issue is in the "initialization" code 
         our @arrayAoH = "";

        [download]
        The problem is that this doesn't just create an array. It creates an array with a single element that contains an empty string. It's basically equivalent to 
        our @arrayAoH;
$arrayAoH[0] = "";

        [download]
        The solution is to either leave out the assignment or to assign it an empty list (which is different from an empty string): 
        our @arrayAoH = ();

        [download]
        More formally, a simple scalar value in list context is treated as a list of length one containing that value.
[reply]
[d/l]
[select]
Re: Array of hashes reference problem
by injunjoel (Priest) on Jun 22, 2005 at 18:04 UTC
    Greetings all,
    Aside from suggesting Data::Dumper or Dumpvalue for complex data-structure investigations I think a read up on perldsc would be worthwhile.
    However my short answer is to make sure that $key contains something prior to the assignment.

    -InjunJoel
    "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo
[reply]
      Thank you for your reply. I'll re-read the DSC.

      I just stepped through the code with Komodo, and I'm absolutely sure that both $key and $value have values in them. Does it matter that $key contains a string with a space in the middle (like 'Foo Bar')? Any other suggestions?

      Thanks
      tl

[reply]
        hi! I ran the following code and it executed without error;
        Please check the input.
        did not check the result but did not get error when executed; 
        use strict;


my $i = 0; <br>
my $j = 0; <br>
my @discovered;<br>
my  @arrayAoH;<br>
<br>
@discovered =(" : hfjfda","rk qjhre:kjfsngfnfd","sdfjlksjf : sfljkhegl
+erg"); <br>
<br>
my $key;<br>
my $value;<br>

until ($i eq $#discovered){<br>
if ($discovered[$i] =~ m/Item Number:/){<br>
until ($discovered[$i] eq ""){<br>
($key, $value) = split /:\s*/, $discovered[$i];<br>
$arrayAoH[$j]{$key} = $value;<br>
$i++;<br>
}<br>

if (($arrayAoH[$j]{"Model Number"} !~ m/^Foo/)){<br>
splice (@arrayAoH, $j, 1);<br>
}<br>
else {<br>
$j++;<br>
}<br>
}<br>
else {<br>
$i++;}<br>
}<br>

        [download]
[reply]
[d/l]

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