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

I am having a problem using hidden() to generate hidden fields in forms. Here is a swatch of code to demonstrate my problem: 
#!/usr/bin/perl

use warnings;
use strict;
use CGI qw/ :standard /;

print hidden(
    -name => "foo",
    -default => "bar",
), "\n";

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When I run this code with the `foo' parameter defined, I get bad results. For example: 
> ./hidden.pl # the code above
<input type="hidden" name="foo" value="bar" />
> ./hidden.pl foo=123
<input type="hidden" name="foo" value="123" />

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The value of the hidden input changes based on the pre-existing values. I see that one can use hidden() to retrieve values but I simply want to define a new one at this point. The `hidden ( $name, $value )' usage functions in the same way.

Perldoc says:
Note, that just like all the other form elements, the value of a
hidden field is "sticky".  If you want to replace a hidden field
with some other values after the script has been called once youll
have to do it manually:

     $query->param(hidden_name,new,values,here);

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Destroying CGI parameters in order to insert hidden fields does not seem reasonable to me. There must be a bettery way. Is there a way to overcome this problem simply? And is there some reasoning behind the way things currently are?

Thanks in advance.

Replies are listed 'Best First'.
Re: Hidden fields using CGI
by eric256 (Parson) on Apr 12, 2004 at 16:45 UTC

    You can use the -override parameter to force it to use the default value.

    use strict;
use warnings;
use CGI qw/ :standard /;
 
print hidden(
       -name => "foo",
       -default => "bar",
   ), "\n";
   
print hidden(-name => "baz", -default => "bab" , -override => 1), "\n"
+;

__DATA__
C:\test>perl cgi.pl foo=test baz=test
<input type="hidden" name="foo" value="test" />
<input type="hidden" name="baz" value="bab" />

C:\test>perl cgi.pl
<input type="hidden" name="foo" value="bar" />
<input type="hidden" name="baz" value="bab" />

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    ___________
    Eric Hodges
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[d/l]
[select]
      Ah, that does the trick, thank you. Now that I know the keyword, I see it all over the documentation.
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Re: Hidden fields using CGI
by Ovid (Cardinal) on Apr 12, 2004 at 16:48 UTC

    If I understand you correctly, you want to add to the hidden fields rather than overwrite them. In that case, why not add the original values back to the parameter?

    $query->param($hidden_name,
  $query->param($hidden_name),
  @plus_the_new_values
);

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    Cheers,
    Ovid

    New address of my CGI Course.

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[d/l]

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