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

This is the revised question and code, many thanks go to jepri for all the changes, and the obvious mistake I made (didn't use strict;) anyways, on to the real question, but first a little background. I am creating a simple news database program that saves to a DBM style database, and can add entries into it, using hashes. I am also using HTML::Template for the first real time to seperate the code from the HTML. My question is, how can I have this code snippet display all of the database entries in a table? Also a second question I have about implementing this type of code, is: how can I display all the entries in a form where each of the contents of each hash row is seperated ... like by using split? Thanks for any help! note:I have not added the file lock yet, but that will be added before I actually use this code in a bigger project later. I am sure that there is a lot of the program that could be much more efficient than it is, if so, please let me know, so I can learn and fix it! Thanks again.

Here is the first file, the actual code file (news.pl): 

#!/usr/bin/perl -w
use strict;
use HTML::Template;
use CGI qw (:standard);
use CGI::Carp qw(fatalsToBrowser);
use DB_File;

my @fields = ("title","date","author","news");
my $q = new CGI;
print $q->header;

my $template = HTML::Template->new(filename => 'news.tmpl');

my $filename="database.db";
tie(my %hash, "DB_File", $filename) or die "Can't open $filename: $!";

#add(); Temporarily not used.

my @loop_data = ();  # initialize an array to hold your loop
my @keys = ();
my @values = ();

while ((my $key, my $value) = each my %hash) {
  push(@keys, $key);
  push(@values, $value);
}

while (@keys and @values) {
  my %row_data;
  
  $row_data{KEY} = shift @keys;
  $row_data{VALUE} = shift @values;

  push(@loop_data, \%row_data);
}

#delete(); Temporarily not used.
untie %hash;

$template->param(
    SHOW_ALL_LOOP => \@loop_data);

print $template->output;

sub add {
  my $key = time();
  my $record = $key;
  foreach my $field(@fields){
    $record  .= "\|$field";
  }
  $hash{$key}  = "$record";
}

sub delete {
  %hash = ();
}

[download]


And here is the HTML Template file for the code (news.tmpl): 

<html>
<head><title>News</title></head>
<body bgcolor=#eeeeee>
<center>

<TMPL_LOOP NAME="SHOW_ALL_LOOP">
  <table width=400 border=1 cellspacing=0 cellpadding=0>
  <tr><td valign=top bgcolor=#dddddd>
  <b>Key</b>:<TMPL_VAR NAME="KEY"><br>
  <b>Value</b>:<TMPL_VAR NAME="VALUE"><br><br>
  </td></tr>
  </table><br>
</TMPL_LOOP>

</center>
</body>
</html>

[download]


That should be all you need to check this program. By the way, this is not a homework question, this is a question that I would like to figure out how to do this sort of program correctly, because last summer I created a web framework news type of thing, but it sucked, and I am hoping this will be better overall than my last project. The old project's site page is at www.hashes.f2s.com ... but it is terrible ^_- so don't see it.

Andy Summers

Replies are listed 'Best First'.
map can help you
by larryk (Friar) on Dec 29, 2001 at 19:55 UTC
    An optimisation for you using map:

    Replace the following 

    my @loop_data = ();
my @keys = ();
my @values = ();

# incidentally, the "my %hash" on the next line should be just "%hash"

while ((my $key, my $value) = each my %hash) {
  push(@keys, $key);
  push(@values, $value);
}

while (@keys and @values) {
  my %row_data;
  
  $row_data{KEY} = shift @keys;
  $row_data{VALUE} = shift @values;

  push(@loop_data, \%row_data);
}

    [download]
    with... 
    my @loop_data = map { { KEY => $_, VALUE => $hash{$_} } } keys %hash;

    [download]
    map is a way to build lists from lists. in this case you can use it to iterate through the keys of %hash and create a hashref for each key/value pair to be stored in @loop_data.

    Don't be confused by the { { ... } } syntax though - map likes a block (i.e. map { ... } list) or a single expression (i.e. map expression, list - notice the comma) but since you want hashrefs ({})we have to use a block or it will get confused when you put a comma after. Maybe I just confused you even more - RTFM and you should see what I mean.

    Hope this helps.

    Update

    Regarding your actual question I think if you put the loop inside the <table></table> around the rows then it'll all be in the same table - is that what you were asking? Sorry, I'm feeling a bit thick today! 

    <table width=400 border=1 cellspacing=0 cellpadding=0>
  <TMPL_UNLESS SHOW_ALL_LOOP>
  <tr>
    <td>
      Nothing to see here folks, move along!
    </td>
  </tr>
  </TMPL_UNLESS>
  <TMPL_LOOP SHOW_ALL_LOOP>
  <tr>
    <td valign=top bgcolor=#dddddd>
      <b>Key</b>:&nbsp;<TMPL_VAR NAME="KEY">
      <b>Value</b>:&nbsp;<TMPL_VAR NAME="VALUE">
    </td>
  </tr>
  </TMPL_LOOP>
</table><br>

    [download]

    Update 2

    Check out DB_File::Lock for obvious reasons.

    Update 3

    For your second question you could just put the template vars in separate table cells: 

        <td valign=top bgcolor=#dddddd>
      <b>Key</b>:&nbsp;<TMPL_VAR NAME="KEY">
    </td>
    <td>
      <b>Value</b>:&nbsp;<TMPL_VAR NAME="VALUE">
    </td>

    [download]
       larryk                                          
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