Class::Meta::Declare is a Perl module deprecated in favor of Class::Meta::Express.

SYNOPSIS

This was a first attempt at making a saner interface for Class::Meta. It is nicer, but Class::Meta::Express is nicer still. Go use that one.

package MyApp::Thingy;
use Class::Meta::Declare :all;
use Data::UUID;

Class::Meta::Declare->new(
meta => [
key => thingy,
accessors => $ACC_SEMI_AFFORDANCE,
],
attributes => [
pi => {
context => $CTXT_CLASS,
authz => $AUTHZ_READ,
default => 3.1415927,
},
id => {
authz => $AUTHZ_READ,
type => $TYPE_STRING,
default => sub { Data::UUID->new->create_str },
},
name => {
required => 1,
type => $TYPE_STRING,
default => No Name Supplied,
},
age => { type => $TYPE_INTEGER, },
],
methods => [
some_method => {
view => $VIEW_PUBLIC,
code => sub {
my $self = shift;
return [ reverse @_ ];
},
}
]
);

my $object = MyApp::Thingy->new;
print MyApp::Thingy->pi; # prints 3.1415927
print $object->name; # prints "No Name Supplied;
$object->set_name("bob");
print $object->name; # prints "bob"

This class provides an alternate interface for Class::Meta.

Class::Meta is a useful module which allows one to create Perl classes which support introspection (also known as reflection). Typically Perl classes, when created, dont supply a lot of metadata. Imported helper functions show up when you call $object->can($method). Private, protected and trusted methods are not readily supported. Fetching a list of attributes or methods is a haphazard affair. Class::Meta overcomes these shortcomings by building the classes for you and allowing you to fetch a class object:

my $class_object = $object->my_class;

foreach my $attribute ( $class_object->attributes ) {
print $attribute->name, "n";
}
foreach my $method ( $class_object->methods ) {
print $method->name, "n";
}

If youve set up your class correctly, these properties are now easy to discover.

Unfortunately, many find the Class::Meta interface to be a bit clumsy. As an alternative, Class::Meta::Declare allows you to declare your entire class in a single argument list to the constructor and have the class built for you automatically. Further, reasonable defaults are provided for just about everything.

IMPORTANT: You want this class or Class::Meta if you need an introspection API for your classes. If you do not need introspection or dynamic class generation, these modules are overkill.