How do I make a new Moose class and instantiate an object of that class at runtime?

Question

After creating a metaclass using Moose::Meta::Class->create, how do I instantiate a real Moose class with that class as a metaclass? (I need to create the metaclass also because I also want to apply some roles to it.)

Answer 1

Not sure this answers this or your other SO question How do I build a Moose class at runtime, add a method to it, apply a role to it and instantiate it once? How would you approach this? at Building a Moose class at runtime and tuning it but have a look at:

• MooseX::SingletonMethod

It may do what you want. Or you may find it useful to peer into our it works.

The documentation does provide links to blog posts I made while coming to grips with building this module so you may find those helpful also.

Here is an brief code example of MooseX::SingletonMethod:

{
    package Foo;
    use MooseX::SingletonMethod;
    sub bar { say 'bar' }
}

my $baz = Foo->new;
my $bar = Foo->new;

$baz->add_singleton_method( baz => sub { say 'baz' } );

$baz->bar;   # => bar
$bar->bar;   # => bar

$baz->baz;   # => baz
$bar->baz;   # Throws can't find baz error

/I3az/

Answer 2

The metaclass is the class, of course. If you want an instance of that class, just do:

my $instance = $meta->name->new

You might also need to make sure that $meta doesn't get collected too soon. Generally, you do this:

$meta->add_method( meta => sub { $meta } );

That will keep the metaclass around, but you're going to leak the class if you aren't careful. If you only do this once, it won't matter; if you do it thousands of times, you could get yourself into trouble.

Much better to use something higher-level like Moose::Meta::Class::create_anon_class or MooseX::Traits.