Actually Class::MOP does not provide for a (direct) way to add methods to an instance, it mostly deals with just classes. And with Moose, there is no way to add a single method on a per-instance basis really either, you do it with runtime Roles instead, like this:
{
package My::Class;
use Moose;
sub hello { "Hello" }
package My::Role;
use Moose::Role;
sub foo { "Foo" }
}
my $obj_1 = My::Class->new;
my $obj_2 = My::Class->new;
My::Role->meta->apply($obj_1);
print $obj_1->foo; # print "Foo"
print $obj_2->foo; # dies with a method not found error
Also
Class::Trait does this same type of thing using Traits instead of Roles.
Ruby accomplishes this type of thing with "Eigenclasses" which were in the Perl 6 metamodel at one time, but were not backported to Moose (because they tended to make simple metaclass things overly complex). The Ruby idiom of:
class << obj
def new_method
"fweeee"
end
end
roughly translates into this:
obj.add_singleton_method(lambda { "fweee" })
where
add_singleton_method is just a method in
Object. Something like this could be added to
Moose without too much trouble at all really (no AUTOLOAD tricks needed either).
