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

I've been working on a new script and unfortunately come to a brick wall.

Basically I have a variable with a numerical value in it (ex. $food = "5";) that's passed to a subroutine.

Alright, so far so good.

But now I need the variable's contents (5) to be used in a new variable, which is assigned to something else.

Ex. $work_5 = "plumbing";

I've looked around but still can't find any solutions to my problem, although I'm sure it's simple.

Any help is greatly appreciated, Thanks!


Kevin
  • Comment on Using variable contents in new variable name

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Re: Using variable contents in new variable name
by imp (Priest) on Dec 11, 2006 at 02:07 UTC
    Perl allows this through symbolic references... but their use results in messy code that is difficult to maintain, and violates strict (which should always be used).

    You should use a different type of data structure instead - arrays and hashes are very appropriate here. 

    my @work_array;
$work_array[5] = "plumbing";

my %work_hash;
$work_hash{5} = "plumbing";

    [download]
[reply]
[d/l]

      If it turns out that you actually need symbolic references, and still want to use strict, you can put a "no strict refs" just before the symbolic reference work, which will temporarily disable strictness for symbolic references. Remember to re-enable them, though!

[reply]
        Remember to re-enable them, though!

        Do it only in the scope of a small code block

        use strict;
...
# strict in effect here
...
{
    no strict q{refs};
    # strict refs not in effect in the scope
    # of this code block so do something with
    # symbolic refs here
    ...
}
...
# strict refs back in effect again without having
# to remember to re-enable it.
...

        [download]

        But, as imp says, don't go there if you can possibly help it.

        Cheers,

        JohnGG

[reply]
[d/l]
Re: Using variable contents in new variable name
by McDarren (Abbot) on Dec 11, 2006 at 02:16 UTC
    As imp points out, you really don't want to do this.
    Have a read of this excellent article by Dominus to understand why not.

    What you probably need instead is a hash. If you are not sure how to implement this, post a short snippet of the actual code.

    Cheers,
    Darren :)

[reply]
      Yeah, I had a feeling what I needed was a hash but like you said, I have no idea how to implement it in this situation.

      Not sure how much this snippet will help (I'm also working in Tk) but: 

      ## This is the button that initiates the sub ADMISSION

$COLUMN_1->Button(-image=>$admiss_1, 
          -width=>179,
          -border=>0,
          -background=>'#c2d297',
          -relief=>'flat',
          -command=>sub{ ADMISSION('1') } )
              ->pack(-side=>'top');

## This is part of the sub ADMISSION that contains a text field ($name
+field) that the variable "$admiss_?_name" needs to be assigned to.(Wi
+th the question mark being replaced by the "1" being passed by the bu
+tton)

sub ADMISSION {
    $namefield->Text(-width=>30,-height=>1)->pack();
        }

      [download]
      So ideally, the text field in the sub would be assigned like this

      $admiss_1_name = $namefield->Text(-width=>30,-height=>1)->pack();

      Thanks for your help guys!
[reply]
[d/l]
[select]

        Your sample line becomes:

        $admiss_ref->{name} = $namefield->Text(-width=>30,-height=>1)->pack();

        [download]

        Or if, as seems to be the case, there are a number of these things in an array you could:

        $COLUMN_1->Button(,
          ...
          -command=>[\&ADMISSION, \%admiss, 1])
              ->pack(-side=>'top');

...

sub ADMISSION {
    my ($admiss_ref, $index) = @_;

    $admiss_ref->[$index]{name} = ...
}

        [download]
        DWIM is Perl's answer to Gödel
[reply]
[d/l]
[select]
Re: Using variable contents in new variable name
by GrandFather (Saint) on Dec 11, 2006 at 02:23 UTC
[reply]

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