http://qs1969.pair.com?node_id=215933

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

Hello,
I am trying to have my script go through some
variables without the variable names being there until
the code is run. I think this is late-binding but i am
not entirley sure. Here is what i want to do.
my result_temp="";
foreach my $test (@testarray)
{
     if(!defined($result_temp = $session->getrequest(
             -varbindlist => ['$'.%cmd_table{$test}]
)))
{
print ("error in session:%s", %cmd_table{$test});
$result_temp="error";
}
push @RESULTS, @result_temp;
}

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What the code would look like that is late-bound is 
-varbindlist => [$myvariable]

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but what will the perl interpreter see?
cause the variable names are all in cmd_table hash
referenced by a number (where test_array is a array of
command numbers. Is there a way to so what i want?
Thanks.
Enigmae

Replies are listed 'Best First'.
Re: using variables in late contexts?
by Eimi Metamorphoumai (Deacon) on Nov 26, 2002 at 22:46 UTC
    Although the other replies will probably work, the idea is probably misguided. There are very, very few places where it's a good idea to use variables for variable names, and this isn't one of them. Try to rewrite your code using a hash instead. See mjd's excellent post for more information.
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Re: using variables in late contexts?
by robartes (Priest) on Nov 26, 2002 at 22:37 UTC
    Your code should work, except that you need to replace: 
    %cmd_table{$test}

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    by 
    $cmd_table{$test}

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    You are refering to the value of a hash entry, not the hash itself, that's why you need $.

    Oh, and there is no need for the @testarray (at least not in this snippet): just loop over the keys of %cmd_table, as in: 

    foreach $test (keys %cmd_hash) {
  # do your thing
}

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    Hope this helps.

    CU
    Robartes-

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Re: using variables in late contexts?
by jreades (Friar) on Nov 26, 2002 at 22:34 UTC

    Let me see that I have this straight.

    You want your code to 'look' like:

    -varbindlist => [$myvariable]

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    Where the input would be:

    -varbindlist => [${$some_variable}]

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    And the input $some_variable would be derived from a value in %cmd_table.

    In that case, I think that the answer is simply:

    my @RESULTS = ();
my $test;
foreach $test (@test_array) {
     my $temp = $session->getrequest(
          -varbindlist => [${$cmd_table{$test}}]
     );
     unless (defined $temp) {
          print("Error in session: %s", $cmd_table{$test});
          push @RESULTS, "error";
     } else {
          push @results, $temp;
     }
}

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    Reformat for personal style.

    Also note that this will probably cause some issues if you use strict since you're interpolating variable names which could result in various security issues.

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