Odd (literally) problems with HTML::Template and params

[legLess]

Monks ~

I'm writing a script with CGI and HTML::Template. This code:

$template->param( STYLE_SHEET       => "$STYLE_SHEET",
                  SCRIPT_LOCATION   => "$SCRIPT_LOCATION",
                  MEMBER_NAME       => $q->param('realname')
                 );

Produces an error ("You gave me an odd number of parameters to param()!") if $q->param('realname') isn't defined. Set $q->param('realname') to 0 (or anything else) and everything's fine.

First question
This code:

$template->param( MEMBER_NAME       => $q->param('realname')
                 );

Produces no errors with identical input. Why? As long as MEMBER_NAME is the only parameter, it seems not to matter if $q->param('realname') defined or not. It's only when there are other parameters that I get the error. The error itself makes a sort of sense, but this seems inconsistent.

Second question
One solution to this is to explicitly set every parameter to 0 if it's not defined. This is possible, but inelegant, and a headache. I like that Perl assumes false if something's undefined. Am I missing something?

Third question
This code is kind of ugly, especially compared with assigning to a hash slice (@row is a row returned from a database):

if (@row) {
    $q-param( mid        => $row[0],
              name       => $row[1],
              realname   => $row[2],
              email      => $row[3]
             );
}

And if, as in question 2 above, I set every param to 0 if it was undefined, I'd have to add something like this:

} else {
    $q-param( mid        => 0,
              name       => 0,
              realname   => 0,
              email      => 0
             );
}

Surely there's a better way?

TIA
--
man with no legs, inc.

[bikeNomad]

The problem is that param() is sensitive to context. If you call it in a list context (which you are), and there's no value, then it returns an empty list (that is, zero items). This is different than returning undef (which would be one item). If you really want just one item from param(), call it in scalar context:

$template->param( STYLE_SHEET       => "$STYLE_SHEET",
                  SCRIPT_LOCATION   => "$SCRIPT_LOCATION",
                  MEMBER_NAME       => scalar( $q->param('realname') )
                 );

[legLess]

*Cough* Gee, legLess, does the work "duh" mean anything to you? Thanks for the gentle clue-stick, bikeNomad.
--
man with no legs, inc.

[LD2]

To clear parameters - use the clear_params() function. Also for more information, you may want to check out:
• jeffa's HTML::Template Tutorial
• HTML::Template
• Google
.
I believe one way to deal with the failure of one param out of many is using the die_on_bad_params option and set it to 1 - although, it's probably not the best way. I'd use bikeNomad's suggestion.

[bwana147]

For the 3rd question, you want to assign to different hash elements the values of a list? You can use a counter (and take care of missing values with an ||):

if ( @row ) {
    my $counter = 0;
    $q->param(
        map { $_ => $row[$counter++] || '' } qw/mid name realname emai
+l/
    );
}

Don't know if it's more legible though.

--bwana147

[legLess]

Oooh - very pretty. Thanks!
--
man with no legs, inc.

[PrakashK]

What version are you using? This problem is fixed in version 2.2 and greater (I believe the current version is 2.3).

/prakash

[legLess]

My host is using 1.7; I'm trying to get them to upgrade.
--
man with no legs, inc.