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use strict;
use warnings;
package MooseX::SetOnce;
our $VERSION = '0.100471';
# ABSTRACT: write-once, read-many attributes for Moose
package MooseX::SetOnce::Attribute;
our $VERSION = '0.100471';
use Moose::Role 0.90;
before set_value => sub { $_[0]->_ensure_unset($_[1]) };
sub _ensure_unset {
my ($self, $instance) = @_;
Carp::confess("cannot change value of SetOnce attribute")
if $self->has_value($instance);
}
around accessor_metaclass => sub {
my ($orig, $self, @rest) = @_;
return Moose::Meta::Class->create_anon_class(
superclasses => [ $self->$orig(@_) ],
roles => [ 'MooseX::SetOnce::Accessor' ],
cache => 1
)->name
};
package MooseX::SetOnce::Accessor;
our $VERSION = '0.100471';
use Moose::Role 0.90;
around _inline_store => sub {
my ($orig, $self, $instance, $value) = @_;
my $code = $self->$orig($instance, $value);
$code = sprintf qq[%s->meta->get_attribute("%s")->_ensure_unset(%s);\n%s],
$instance,
quotemeta($self->associated_attribute->name),
$instance,
$code;
return $code;
};
package Moose::Meta::Attribute::Custom::Trait::SetOnce;
our $VERSION = '0.100471';
sub register_implementation { 'MooseX::SetOnce::Attribute' }
1;
__END__
=pod
=head1 NAME
MooseX::SetOnce - write-once, read-many attributes for Moose
=head1 VERSION
version 0.100471
=head1 SYNOPSIS
Add the "SetOnce" trait to attributes:
package Class;
use Moose;
use MooseX::SetOnce;
has some_attr => (
is => 'rw',
traits => [ qw(SetOnce) ],
);
...and then you can only set them once:
my $object = Class->new;
$object->some_attr(10); # works fine
$object->some_attr(20); # throws an exception: it's already set!
=head1 DESCRIPTION
The 'SetOnce' attribute lets your class have attributes that are not lazy and
not set, but that cannot be altered once set.
The logic is very simple: if you try to alter the value of an attribute with
the SetOnce trait, either by accessor or writer, and the attribute has a value,
it will throw an exception.
If the attribute has a clearer, you may clear the attribute and set it again.
=head1 AUTHOR
Ricardo SIGNES <rjbs@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2010 by Ricardo SIGNES.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut
|
