Zarabozo, Francisco (GE, Corporate) <> wrote:
> Hello All,
>
> I'm having some trouble with a module where I need to implement a
> change.
> Basically, this module defines constants that other modules will use
> at a later time.
>
> I need to detect parameters in the import() sub (that's the requested
> change) and, if the case, redefine some of those constants.
>
> I'm trying with evals but all I'm getting is a warning about
> "constant redefined", AND the constant is not really changing (it
> keeps its previous value).
No. It will be complaining about a subroutine being redefined.
>
> Is there a way to correctly redefine a constant at import() time?
I would hope not! That would subvert the whole concept of a constant.
However, ...
>
> Here is a simple example of the scene:
>
> Script.pl
> -----------------
> use strict;
> use warnings;
> use myModule constantA => 'foo';
> -----------------
>
> myModule.pm
> -----------------
> package myModule;
> use strict;
> use warnings;
> use constant constantA => 'bar';
>
> sub import {
> my %params = @_;
> if ($params{constantA}) {
> # This should change constantA from 'bar' to 'foo'
> eval 'use constant constantA => \''.$params{constantA}.'\'';
> warn $@ if $@;
> }
> }
> -----------------
>
> Any comments are highly appreciated.
While this appears to do what you want (at least it does after
modification), the warning about redefinition of a subroutine may be
hard to inhibit without changing constant.pm. One way would be to avoid
redefining any subroutines, e.g.
------------------------
use strict;
use warnings;
package myModule;
our %defaults = (constantA => 'bar');
sub import {
my $module = shift;
my %params = @_;
foreach my $k (keys %defaults) {
my $val = defined($params{$k}) ? $params{$k} : $defaults{$k};
eval qq{use constant $k => '$val'};
warn $@ if $@;
}
}
1;
--------------------------
Its not entirely clear what you are trying to achieve, but I don't think
that variable constants (i.e. constants that are not constant) is a good
way to do it.
HTH
--
Brian Raven
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