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

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John Macdonald
August 9, 2015 20:57
RE: 'around' method modifier does not seem to work
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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:

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

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

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

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

John Macdonald
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Ontario Institute for Cancer Research
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From: Chris Prather []
Sent: August 7, 2015 12:27 PM
To: Marcos Barbeitos
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);

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

On Thu, Aug 6, 2015 at 7:04 PM, Marcos Barbeitos <<>> wrote:


I looked up the behavior of the modifier 'around' in <>, 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

Phone: (55 41) 3361-1634

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