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Re^2: symbolic variables

by Anonymous Monk
on Jan 04, 2008 at 02:07 UTC ( #660363=note: print w/replies, xml ) Need Help??

in reply to Re: symbolic variables
in thread symbolic variables

yikes, i have to resort to them whenever i want to have "generic" logi +c that deals with a multitude of routines. i use symbolic references for : object methods dispatch tables and in most unit test scripts If you have a better alternative; i'll consider it!

object methods : i use anonmyous routines for the methods that deal with scalar attributes.

package <>; our $scalarMethods; @{ $scalarMethods } = qw( name ); foreach my $attributeScalar ( @{ $scalarMethods } ) { no strict "refs"; *$attributeScalar = sub { my $subName = $package . "::$attributeScalar"; if ($VRB) { print " $subName \n"; } my ($self) = shift; if (@_) { $self->{$attributeScalar} = shift; } return $self->{$attributeScalar}; } }

dispatch tables : a generic manner to call routines in a package

for ( $ndx=0; $ndx<=0; $ndx++ ) { no strict 'refs'; ($kgDATA,$pmDATA) = &{ "cktTmplt_utils::$SUB" }($ndx );

unit test scripts : within the <>.t script

# are package variables accessible ? no strict "refs"; foreach my $pkg ( @{ $filePackages } ) { for ( my $i=0; $i<=1; $i++ ) { ${ $pkg . "::VRB" } = $i; is( $i, ${ $pkg . "::VRB" }, "GLBL VAR : VRB" ); ${ $pkg . "::TST" } = $i; is( $i, ${ $pkg . "::TST" }, "GLBL VAR : TST" ); } ${ $pkg . "::VRB" } = 1; # no STDOUT durings tests ${ $pkg . "::TST" } = 1; # return data and don't execute } use strict "refs";

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Re^3: symbolic variables
by Corion (Pope) on Jan 04, 2008 at 08:22 UTC

    Your first use to generate scalar methods is an OK use of symbolic references, because the way to create a named subroutine without using symbolic references is far more unwieldly:

    $::My::Package::{$attributeScalar} = sub {...};

    But why aren't you using Class::Accessor or any of the other modules which create such accessors for you?

    Using symbolic references in dispatch tables is convenient until you need to think about which subroutines are to be called dynamically and which not. Using hard references in a hash is self-documenting and more secure, and allows for renaming of the exported name:

    use vars qw(%user_methods); %user_methods = ( handle_foo => \&handle_foo, handle_bar => \&handle_bar, handle_baz => \&do_handle_baz, ); ... sub handle { my $data = shift; for my $filter (@_) { if (exists $user_methods{ $filter }) { $data = $user_methods{ $filter }->($data); } else { die "Unknown filter method '$filter'"; }; }; };

    Your third test will always succeed - you can always set global package variables. Also, I would ditch the C-style for loop in favour of:

    for my $i (0..1) {

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[choroba]: Isn't Using PerlPod Creatively rather a meditation?
[choroba]: I don't see a question
[1nickt]: ugh, I stuck my head in the bass bin for 30 seconds on a dare at Ted Nugent at Hammersmith Odeon. Yes, I am 40% deaf now.
[johngg]: My daughter is incredibly jealous of my wife who got to see The Clash at Brixton many years ago. They went to see The Vaccines there recently.
[1nickt]: But the bands are even louder! I saw Spearhead (Michael Franti) at an outdoor show and had to walk a mile away to not feel pain in my chest! Babies were crying ... I asked the sound engineer why it was necessary to have the bass so loud and he laughed...
[Discipulus]: but the best i attended live was Mano Negra Patchanka at Forte Prenestino .. in 1990
[Corion]: Hmmm - Mano Negra or at least Manu Chao seem to put on a good live show. At least the one live CD I have from Manu Chao sounds good ;)
Discipulus feels the same jealousity of the johngg's daughter
[1nickt]: choroba I agree
[choroba]: Playing in a punk rock band for 20 years... my hearing is quite bad

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