Question

I have the following five Moose attributes:

has ['summary_file', 'html_file', 'url1', 'url2', 'txt_file'] => (
    is       => 'rw',
    isa      => 'Str',
    required => 0,
    lazy     => 1,
    default  => sub { confess "Attribute not set"; },
    );

I would like to:

1. Make each of them use its own builder (e.g. set 'summary_file' use _build_summary_file, etc.)
2. Make the default confess sub state which (uninitialized) attribute was called (e.g. "Attribute 'summary_file' not set").

I can accomplish the above by writing five separate has‘s, but perhaps there’s a more compact way?

Answer 1

You could do something the like following (new working example after your “does not work” comment below):

package My::Class;
use Moose;
use namespace::autoclean;

for my $attr (qw(x y)) {
    has $attr => (
        is       => 'rw',
        isa      => 'Str',
        required => 0,
        lazy     => 1,
        builder  => "_build_$attr",
    );
}

sub _build_x { rand }
sub _build_y { rand }

__PACKAGE__->meta->make_immutable;

package main;

use strict; use warnings;

my $o = My::Class->new;

print $o->$_, "\n" for qw(x y);

Note that you cannot specify both a default and a builder.

@Oesor points out in a comment something I forgot:

has ['summary_file', 'html_file', 'url1', 'url2', 'txt_file'] => (
    is         => 'rw',
    isa        => 'Str',
    required   => 0,
    lazy_build => 1,
);