I came to this Is there an advantage to storing references to objects in an attribute instead of the object itself?. Applying find_cycle from Devel::Cycle in my own script showed that I had a lot of circular references.

I realized most of them were due to storing "external" objects' reference in $self current object, many of these were in fact not needed in methods call. But in some methods I had to use an object received in the constructor.

See for example the code below. The circular reference is suppress with a call to weaken (but the second call to do_something fails).

use strict;
use warnings;
use Devel::Cycle;

package A;

sub new {
    my ( $class, $href ) = @_;
    my $self = { dbi => $$href{dbi} };
    $self->{helper} =
        Helper->new( helper_function => sub { $self->this_is_from_A(@_
+) } );
    bless $self, $class;
  
}

sub do_something {
    my $self = shift;
    $self->{helper}->called_from_helper();
}

sub this_is_from_A {
    my ( $self, $arg ) = @_;
    print "$arg\nthis_is_from_A using $self->{dbi}\n";
}

package Helper;
#use Scalar::Util qw/weaken/;
sub new {
    my $class = shift;
    my %def   = ( a => "something" );
    my %arg   = ( ref $_[0] eq "HASH" ? ( %def, %{ $_[0] } ) : ( %def,
+ @_ ) );
    my $self  = \%arg;
    bless $self, $class;
}

sub called_from_helper {
    my $self = shift;
    print "called_from_helper\n";
    $self->{helper_function}->("param from Helper");
    #weaken($self->{helper_function});
}

package main;
my $a = A->new( { dbi => "some dbi object" } );
$a->do_something();
$a->do_something();
find_cycle($a);
[download]

Using a sub ref instead of a method calls to this_is_from_A in the code ref pass with helper_function eliminates the circular reference because the code can access the $href->{dbi} directly.

use strict;
use warnings;

use Devel::Cycle;

package A;

sub new {
    my ( $class, $href ) = @_;
    my $self = { dbi => $$href{dbi} }; 
    $self->{helper} =
        Helper->new( helper_function => sub { 
                     print "$_[0]\nthis_is_from_A using $$href{dbi}\n"
+;
            } );
    bless $self, $class;
}

sub do_something {
    my $self = shift;
    $self->{helper}->called_from_helper();
}
=for comment
sub this_is_from_A {
    my ($self, $arg) = @_;
    print "$arg\nthis_is_from_A using $self->{dbi}\n";
}
=cut

package Helper;

sub new {
    my $class = shift;
    my %def = ( a => "something");
    my %arg   = ( ref $_[0] eq "HASH" ? ( %def, %{ $_[0] } ) : ( %def,
+ @_ ) );
    my $self  = \%arg;
    bless $self, $class;
}

sub called_from_helper {
    my $self = shift;
    print "called_from_helper\n";
    $self->{helper_function}->("param from Helper");
}

package main;
my $a = A->new( { dbi => "some dbi object" } );
$a->do_something();
$a->do_something();
find_cycle($a)
[download]

But if the code from this_is_from_A was a long and complicated thing, wouldn't it clutter A->new and make it hard to understand and maintain ? Is there another solution ?

Thanks for any comment

frazap

Update: complete the example 2 (end was missing). Update 2 with the correct lines of code.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.