Hashrefs and arrayrefs

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

Newbie alert. I have done some admin scripts in perl, but now I'm trying my hand at cgi using HTML::Template. Following the tutorial on the sourceforge site for HTML::Template, I created the following code that is supposed to generate a table from a directory listing. It generates the table just fine, but the content of the table is wrong. If there are N items in the directory, I get N rows with the Nth item repeated in each row.

I am obviously missing something. If you need more of the code, just ask.

...snip...
foreach $dir(@dirlist) {
   my $newdir=($dest."\/".$dir);
   if (-f $absdir."\/".$dir) {
   %info=(
       driver =>"working",
     filename=> "<a href=\"../drivers$newdir\">$dir</a><BR>",
       desc =>"working on this, too"
    );
}
   else {
       %info=(
       driver =>"working",
       filename =>"<a href=\"/cgi/index.cgi?$newdir\">$dir</a><BR>",
       desc =>"working on this, too"
                );
    }
    push(@tmplt_list, \%info);
}
[download]

Thanks much, and please be gentle :)

Comment on Hashrefs and arrayrefs Download Code

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Re: Hashrefs and arrayrefs by stephen (Priest) on Apr 19, 2002 at 14:17 UTC
Your problem is that you are pushing the same variable reference into to list over and over. You need to localize `%info` with `my`, like so: `...snip... foreach $dir(@dirlist) { my %info; my $newdir=($dest."\/".$dir); if (-f $absdir."\/".$dir) { %info=( driver =>"working", ...snip...` [download] It's an easy mistake to make... unless you've got `use strict` running. Turn on `use strict`. :) stephen	[reply] [d/l] [select]
Re: Hashrefs and arrayrefs by kappa (Chaplain) on Apr 19, 2002 at 14:40 UTC
TMTOWTDI, as usual :) Change this: `push(@tmplt_list, \%info);` [download] ...to this: `push(@tmplt_list, {%info});` [download] so that you push a reference to a copy of `%info`, not the real `%info` which you change on next iteration.	[reply] [d/l] [select]
Re: Hashrefs and arrayrefs by digger (Friar) on Apr 19, 2002 at 15:11 UTC
As usual TMTOWTDI. Both of your suggestions worked. I am using strict as well as warnings (part of the code I did not post). The issue was I put the `my %info` outside the foreach loop, so it was not localized correctly. Once I moved the %info declaration inside the foreach, presto, it worked. And I understand it. To avoid cargo cult programming, I must ask kappa about the syntax of `push(@tmplt_list, {%info});`. What does the extra set of braces around %info accomplish? Thank you, again	[reply] [d/l] [select]
Re: Re: Hashrefs and arrayrefs by Juerd (Abbot) on Apr 19, 2002 at 15:16 UTC
push(@tmplt_list, {%info}); . What does the extra set of braces around %info accomplish? They create a reference to an anonymous hash, that in this case consists of the same elements as the %info hash. In other words: it copies %info to a hash without a name, and returns a reference to it. Would you want to reference the original %info (which is more efficient but not always what you want), you would use: `push @tmplt_list, \%info;` [download] - Yes, I reinvent wheels. - Spam: Visit eurotraQ.	[reply] [d/l]