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package # hide the package from PAUSE
AttributesWithHistory;
use strict;
use warnings;
our $VERSION = '0.05';
use parent 'Class::MOP::Attribute';
# this is for an extra attribute constructor
# option, which is to be able to create a
# way for the class to access the history
AttributesWithHistory->meta->add_attribute('history_accessor' => (
reader => 'history_accessor',
init_arg => 'history_accessor',
predicate => 'has_history_accessor',
));
# this is a place to store the actual
# history of the attribute
AttributesWithHistory->meta->add_attribute('_history' => (
accessor => '_history',
default => sub { {} },
));
sub accessor_metaclass { 'AttributesWithHistory::Method::Accessor' }
AttributesWithHistory->meta->add_after_method_modifier('install_accessors' => sub {
my ($self) = @_;
# and now add the history accessor
$self->associated_class->add_method(
$self->_process_accessors('history_accessor' => $self->history_accessor())
) if $self->has_history_accessor();
});
package # hide the package from PAUSE
AttributesWithHistory::Method::Accessor;
use strict;
use warnings;
our $VERSION = '0.01';
use parent 'Class::MOP::Method::Accessor';
# generate the methods
sub _generate_history_accessor_method {
my $attr_name = (shift)->associated_attribute->name;
eval qq{sub {
unless (ref \$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}) \{
\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\} = [];
\}
\@\{\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}\};
}};
}
sub _generate_accessor_method {
my $attr_name = (shift)->associated_attribute->name;
eval qq{sub {
if (scalar(\@_) == 2) {
unless (ref \$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}) \{
\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\} = [];
\}
push \@\{\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}\} => \$_[1];
\$_[0]->{'$attr_name'} = \$_[1];
}
\$_[0]->{'$attr_name'};
}};
}
sub _generate_writer_method {
my $attr_name = (shift)->associated_attribute->name;
eval qq{sub {
unless (ref \$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}) \{
\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\} = [];
\}
push \@\{\$_[0]->meta->get_attribute('$attr_name')->_history()->\{\$_[0]\}\} => \$_[1];
\$_[0]->{'$attr_name'} = \$_[1];
}};
}
1;
=pod
=head1 NAME
AttributesWithHistory - An example attribute metaclass which keeps a history of changes
=head1 SYSNOPSIS
package Foo;
Foo->meta->add_attribute(AttributesWithHistory->new('foo' => (
accessor => 'foo',
history_accessor => 'get_foo_history',
)));
Foo->meta->add_attribute(AttributesWithHistory->new('bar' => (
reader => 'get_bar',
writer => 'set_bar',
history_accessor => 'get_bar_history',
)));
sub new {
my $class = shift;
$class->meta->new_object(@_);
}
=head1 DESCRIPTION
This is an example of an attribute metaclass which keeps a
record of all the values it has been assigned. It stores the
history as a field in the attribute meta-object, and will
autogenerate a means of accessing that history for the class
which these attributes are added too.
=head1 AUTHORS
Stevan Little E<lt>stevan@iinteractive.comE<gt>
Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
=cut
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