CODEWITHSUNDEEP
perlooppass-by-reference
Bram Vanroy
Bram Vanroy

Reputation: 28437

Perl method and pass by reference

For me, Perl references are a hard thing to grasp. When reading to some OO-like scripts that use object methods, I never saw the object used as a reference. Even for big objects, that would benefit from being used as a reference instead of being copied to a subroutine (method).

PerlMaven says that:

$p->a_method($value);

Behind the scenes, perl will run

a_method($p, $value);

But if $p is huge object, wouldn't you want to pass it as a reference?

a_method(\$p, $value)

I have always understood that passing by reference can lead to a significant speed increase if the object is large. In OO, it is quite likely that you are working with large objects (e.g. a huge XML::Twig). So how would you call a method on such an object, when actually passing it as a reference to the subroutine?

Upvotes: 0

Views: 395

Answers (1)

choroba
choroba

Reputation: 241858

$p already contains a reference to the object. Method calls require a reference to the object, and it's this reference that's passed to the sub. So, $self is always a reference. See perlobj and bless.

#! /usr/bin/perl
use strict;
use warnings;
use feature 'say';

{   package Class;

    sub new { bless {}, __PACKAGE__ }
    sub inf { ref shift }
}

my $o = 'Class'->new;
say $o->inf ? 'reference' : 'not a reference';

Output:

reference

Upvotes: 9

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