Perl: how to increment a Class::Struct field? - perl

Question

How do I increment a field in a Class::Struct object?
For now I am stuck with
use Class::Struct foo => [
counter => '$',
];
my $bar = foo->new(counter => 5);
$bar->counter($bar->counter()+1);
I wonder if there is something more expressive than the last line (the obvious $bar->counter++ results in Can't modify non-lvalue subroutine call).
EDIT: of course, I am not interested in $bar->[0]++ et al - what if I add a field before counter? I don't want to have to hunt my code for all such "bugs-in-waiting".

Answer 1

You can add an increment method to foo:
#!/usr/bin/env perl
package foo;
use strict; use warnings;
sub increment_counter {
my $self = shift;
my $val = $self->counter + 1;
$self->counter($val);
return $val;
}
package main;
use 5.012;
use strict;
use warnings;
use Class::Struct foo => [
counter => '$',
];
my $bar = foo->new(counter => 5);
$bar->increment_counter;
say $bar->counter;
__END__

Answer 2

Alternatively, try doing this :
use strict; use warnings;
use Class::Struct foo => [
counter => '$',
];
my $bar = foo->new(counter => 5);
print ++$bar->[0];
or using a SCALAR ref (no need to hard-code the "path" like the previous snippet) :
use strict; use warnings;
$\ = "\n";
use Class::Struct foo => [
counter => '*$',
];
my $bar = foo->new(counter => 5);
print ++${ $bar->counter };