On Thu, Apr 15, 2010 at 1:20 PM, Sir Robert Burbridge
<rburb...@cisco.com> wrote:
>
> Ahh, thanks. So typing is basically nomination of classes into a program's
> cosmology. That's super helpful.
>
> Thanks again,
Types work on things other than classes as well. It's more of a way of
saying "This arrangement of Data is special. Here's a name for it."
For example you can define a type that has nothing to do with a class at all:
subtype PersonRecord => as HashRef => where { exists $_->{first_name}
&& exists $_->{last_name} };
This would match: { first_name => 'Cory', last_name => 'Watson' }
but wouldn't match:
class Person::Record { has first => ( accessor => 'first_name' ); has
last => ( accessor => 'last_name' ); }
...
This distinction becomes important when you get into things like
coercions. You can then say something like:
coerce 'Person::Record' => from PersonRecord => via {
Person::Record->new(first = $_->{first_name}, last => $_->{last_name})
};
and create objects from hashes with a minimum of fuss. There are also
things like MatchOnType in Moose::Util::TypeConstraints and other
tools that come into play once you have a good grasp of the Typing
system.
-Chris
