RE: 'around' method modifier does not seem to work

[John Macdonald]

As Ben suggested, setting the attribute is working fine; but any read of the 
attribute sets it to undef.  I added two lines to the end of Chris' test:

...
say $at->dump;
say $at->foo;
say $at->dump;

Now running it gives:

perl test.pl
$VAR1 = bless( {
                 'foo' => 'BAR'
               }, 'AroundTest' );

Use of uninitialized value $seq in uc at test.pl line 13.

$VAR1 = bless( {
                 'foo' => ''
               }, 'AroundTest' );

Write-only attributes are generally not very useful.  :-)


John Macdonald
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________________________________
From: Chris Prather [perig...@prather.org]
Sent: August 7, 2015 12:27 PM
To: Marcos Barbeitos
Cc: moose@perl.org
Subject: Re: 'around' method modifier does not seem to work

So you'll need to provide a reduced example that demonstrates the behavior your 
showing. When I tried to reproduce (with the script below) the attribute was 
being set just fine.

#!/usr/bin/env perl
use 5.12.1;
use warnings;

{

    package AroundTest;
    use Moose;

    has foo => ( is => 'rw' );
    around foo => sub {
        my ( $next, $self, $seq ) = @_;
        $seq = uc($seq);
        $self->$next($seq);
    };
}

my $at = AroundTest->new();
$at->foo('bar');
say $at->dump;




On Thu, Aug 6, 2015 at 7:04 PM, Marcos Barbeitos 
<msbarbei...@gmail.com<mailto:msbarbei...@gmail.com>> wrote:

Howdy,

I looked up the behavior of the modifier 'around' in 
<http://search.cpan.org/~ether/Moose-2.1600/lib/Moose/Manual/MethodModifiers.pod#Around_modifiers>,
 and the code snipet is:

  around 'size' => sub {
      my $orig = shift;
      my $self = shift;

      return $self->$orig()
          unless @_;

      my $size = shift;
      $size = $size / 2
          if $self->likes_small_things();

      return $self->$orig($size);
  };

In my code, I have:

has 'sequence' =>
(
    is => 'rw'
  , isa => 'Str'
  , predicate => 'has_sequence'
);

around 'sequence' => sub
{
    my $orig = shift;
    my $self = shift;
    my $sequence = uc shift;

    # Do lots of things with $sequence and then

    return $self->$orig( $sequence );
}

But the attribute is not set.

I've tried lots of variations of the last line:

$self->$orig( $sequence );
return $orig->( $self, $sequence );
$orig->( $self, $sequence );
return $sequence;

With no success, as expected. However, if I do:

around 'sequence' => sub
{
    my $orig = shift;
    my $self = shift;

    return $self->$orig( @_ );
}

The attribute is set and life goes on. Of course, that does not work for me 
because I need to do a bunch of things to the argument passed to this method.

Any ideas about the reasons for the (apparent?) discrepancy in behavior?

Best wishes and thanks in advance.

--
Marcos S. Barbeitos

Departamento de Zoologia - Sala 360
Setor de Ciências Biológicas
Universidade Federal do Paraná
Caixa Postal 19020
Curitiba, PR 81531-990
Brazil

Phone: (55 41) 3361-1634