in reply to Tk with map - Perl newbie

by adding unneeded complexity you've lost what is happening

why you wrote this way: 

my ($dfHost, $dfPort, $dfUser,$dfPassword) 
    = map {$fRight->Entry(    -textvariable=>$_ )->pack(-side=>'top',-
+pady=>3)}
        qw/\$user \$password/;

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you assign 2-element list to 4 variables, so last two are undefined.

But more to the point, if you'll write 

$fRight->Entry(    -textvariable=>\$user )->pack(-side=>'top',-pady=>3
+);
$fRight->Entry(    -textvariable=>\$password )->pack(-side=>'top',-pad
+y=>3);

[download]
your code works as expected.
I can not explain it, but I know it
:)

(addition) qw/\$user .../ does not do what you want

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Re^2: Tk with map - Perl newbie
by stickleback (Novice) on Mar 31, 2011 at 13:56 UTC
    Thanks for the quick reply.

    The 2 element list to 4 variables was a mistake in extracting the dialog from the larger program. Apologies for that.

    I your suggested broken out code works fine. The following also works ... 

    $dfUser->configure( -textvariable=>\$user);    
$dfPassword->configure( -textvariable=>\$password);

    [download]
    I can get my code to work and the dialog to display correctly but I wanted to understand why the original code does not work. I am trying to learn Perl along the way.
[reply]
[d/l]
      The quoting operator as in qw/\$user \$password/ doesn't work because what is getting translated in to the $_ variable is the TEXT '\$user', not a reference to $user!

      I show this below with a simple example. Using parens and comma for a normal list allows the \$user to be translated into a value that is the reference. The code will expect to deference the hash value and that will work if what is stored is really a reference to something else rather some text. So in this case, the qw// is not doing what (..,...) does. 

      #!/usr/bin/perl -w
use strict;
use Data::Dumper;

my ($user,$password);

my $a=0;
my %hash1 = map{$a++=>$_}qw/\$user \$password/; #just text
my %hash2 = map{$a++=>$_}(\$user, \$password);  #real reference

print Dumper \%hash1, \%hash2;

$user     = 234;
$password = 'xyz';

print Dumper \%hash1, \%hash2;
__END__
$VAR1 = {
          '1' => '\\$password',
          '0' => '\\$user'
        };
$VAR2 = {
          '3' => \undef,  #ref to an undefined val
          '2' => \undef
        };
#################
$VAR1 = {
          '1' => '\\$password',
          '0' => '\\$user'
        };
$VAR2 = {
          '3' => \'xyz', #see changing $user or $password
          '2' => \234    #did update the hash
                         #because these are real references.
        };

      [download]
[reply]
[d/l]
[select]
      (update) deleted wrong content,
      sorry
      :-|
[reply]

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