PERL Beginners - CGI: How do I populate a form field based on the value entered in a different field

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CGI: How do I populate a form field based on the value entered in a different field

Richard Fernandez

2006-09-23, 6:57 pm

Hi folks,

I'm trying to create an HTML form that will refresh itself based on user
input. In the POD for CGI it says that you can set the value of a named
parameter by using something like:

$query->param(-name=>'foo', -value=>'the value');

But it doesn't say (or at least I didn't see) anything about how to
redisplay the form with the new value in the textbox (or a different
textbox for that matter).

The sample script at the top of the doco (perldoc CGI) creates a blank
form that takes some input, a name, a "combination", and a color and
displays the user input in the bottom half of the page.

I would like to edit the value entered into the "name" textbox and
display my edited value in the same, or possibly a different textbox.
I've tried a bunch of things including the call to param() above,
without success.

For example, if the user types "Wilma" into the textbox, the script
should populate the target textbox with my edited value, say, "Betty".

As always, Thanks in Advance for any help!

richf

nobull67@gmail.com

2006-09-23, 6:57 pm

Richard Fernandez wrote:

> I'm trying to create an HTML form that will refresh itself based on user
> input. In the POD for CGI it says that you can set the value of a named
> parameter by using something like:
>
> $query->param(-name=>'foo', -value=>'the value');
>
> But it doesn't say (or at least I didn't see) anything about how to
> redisplay the form with the new value in the textbox (or a different
> textbox for that matter).

If you are using the CGI methods to display the form, and (of course)
you have the code to display the form _after_ the code that alters the
values then is should just happen.

> As always, Thanks in Advance for any help!

As always, please reduce your problem to a minmum but complete script
(that uses strict and warnings) and post it here in it's entirity,
unaltered.

Richard Fernandez

2006-09-23, 6:57 pm

> $query->param(-name=3D>'foo', -value=3D>'the value');

Make that line $query->param(-name=3D>'foo', -value=3D>"$the_value");

Then somwhere at the start where you get the variables;

my $name =3D $query->param('name')||'';

if ($name =3D~/mary/i){ $the_value =3D "Howdy Mary" }

How you do it depends on your workflow/logic

Owen

Thanks for your response, but I still don't get it. I type my name into
the box and click=20
Submit, but it doesn't change!

Could you please clarify?

Here's my code:

#!/usr/bin/perl -w
# This script is the example at the top of the CGI pod --richf;
use strict;
use CGI;

my $html =3D new CGI;

my $new_value;
my $name =3D $html -> param('name') or '';
if ($name =3D~ /richf/i) {
$new_value =3D 'John';
}

print $html -> header,
$html -> start_html('A Simple Example'),
$html -> h1('A Simple Example'),
$html -> start_form,

"What's your name?",
$html -> textfield(-name =3D> 'name'),

$html -> p,
"What's the combination?",
$html -> p,
$html -> checkbox_group(-name=3D>'words',
-values=3D>['eenie','meenie','minie','moe'],
-defaults=3D>['eenie','minie']),
$html -> p,
"What's your favorite color?",
$html -> popup_menu(-name=3D>'color',
-values=3D>['red','green','blue','chartreuse']),
$html -> p,
$html -> submit,
$html -> end_form,
$html -> hr;

$html -> param(-name =3D> 'name', -value =3D> $new_value);
print $html -> end_html;

D. Bolliger

2006-09-23, 6:57 pm

RICHARD FERNANDEZ am Sunday, 24. September 2006 02:15:
>
> Make that line $query->param(-name=>'foo', -value=>"$the_value");
>
> Then somwhere at the start where you get the variables;
>
> my $name = $query->param('name')||'';
>
> if ($name =~/mary/i){ $the_value = "Howdy Mary" }
>
>
>
> How you do it depends on your workflow/logic
>
>
>
> Owen

Hello Richard

> Thanks for your response, but I still don't get it. I type my name into
> the box and click
> Submit, but it doesn't change!
>
> Could you please clarify?
>
> Here's my code:
>
> #!/usr/bin/perl -w
> # This script is the example at the top of the CGI pod --richf;
> use strict;
> use CGI;
>
> my $html = new CGI;
>
> my $new_value;

my $new_value='';

> my $name = $html -> param('name') or '';

This should read:

my $name = $html->param('name') || '';

due to the precedence of the operators: '||' > '=' > 'or'
See

perldoc perlop

('' is never assigned to $new_value with 'or')

And please don't use spaces around '->' :-)

> if ($name =~ /richf/i) {
> $new_value = 'John';
> }
>
> print $html -> header,
> $html -> start_html('A Simple Example'),
> $html -> h1('A Simple Example'),
> $html -> start_form,
>
> "What's your name?",
> $html -> textfield(-name => 'name'),

Here's the source of your problem: the textfield value is missing:

$html->textfield(-name => 'name', -value => $new_value),

> $html -> p,
> "What's the combination?",
> $html -> p,
> $html -> checkbox_group(-name=>'words',
> -values=>['eenie','meenie','minie','moe'],

btw, above line can be written shorter:

-values=>[ qw( eenie meenie minie moe ) ],

> -defaults=>['eenie','minie']),
> $html -> p,
> "What's your favorite color?",
> $html -> popup_menu(-name=>'color',
> -values=>['red','green','blue','chartreuse']),
> $html -> p,
> $html -> submit,
> $html -> end_form,
> $html -> hr;
>
>
>
> $html -> param(-name => 'name', -value => $new_value);

This will only change the value in the request object, but not in the form!
(also part of your problem)

> print $html -> end_html;

Hope this helps!

Dani

Richard Fernandez

2006-09-23, 9:57 pm

Did you test it? It is my impression that CGI.pm works this way
normally:

<snip>

if (param) {

# Replace the parameter.
my $temp =3D param('name');
if ($nmap{$temp}) {
# param('name',$nmap{$temp}); # This also works.
param(-name =3D> 'name', -value =3D> $nmap{$temp});
}

print
"Your name is ",em(param('name')),p,
"The keywords are: ",em(join(", ",param('words'))),p,
"Your favorite color is ",em(param('color')),".\n";
}
print end_html;

Thanks for your response, Mumia.=20

This is very similar to the example in the doc, and it does work, but
what I'm (still) trying to do is replace the name that is typed into the
textfield, not print it outside of the form.

Thanks to all who've responded, so far. I'm still playing with it, but
haven't cracked it yet... I hate getting hung up on something simple.
(maybe what I need is sleep at this point :)=20

richf

Richard Fernandez

2006-09-23, 9:57 pm

Ding! Ding! Ding! I finally got it!!!=20

Not sure why this had me so stumped...

In any case, thanks to all that responded. I appreciate all the help.

richf

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