Provided by: libclass-meta-perl_0.66-3_all 
NAME
Class::Meta - Class automation, introspection, and data validation
SYNOPSIS
Generate a class:
package MyApp::Thingy;
use strict;
use Class::Meta;
BEGIN {
# Create a Class::Meta object for this class.
my $cm = Class::Meta->new(
key => 'thingy',
default_type => 'string',
);
# Add a constructor.
$cm->add_constructor(
name => 'new',
create => 1,
);
# Add a couple of attributes with generated methods.
$cm->add_attribute(
name => 'uuid',
authz => 'READ',
required => 1,
default => sub { Data::UUID->new->create_str },
);
$cm->add_attribute(
name => 'name',
is => 'string',
default => undef,
);
$cm->add_attribute(
name => 'age',
is => 'integer',
default => undef,
);
# Add a custom method.
$cm->add_method(
name => 'chk_pass',
view => 'PUBLIC',
code => sub { ... },
);
$cm->build;
}
sub chck_pass { ... }
Or use Class::Meta::Express for a more pleasant declarative syntax (highly recommended!):
package MyApp::Thingy;
use strict;
use Class::Meta::Express;
class {
meta thingy => ( default_type => 'string' );
ctor 'new';
has uuid => (
authz => 'READ',
required => 1,
default => sub { Data::UUID->new->create_str },
);
has name => ( required => 1 );
has age => ( is => 'integer' );
method chk_pass => sub { ... }
};
Now isn't that nicer? Then use the class:
use MyApp::Thingy;
my $thingy = MyApp::Thingy->new( id => 19 );
print "ID: ", $thingy->id, $/;
$thingy->name('Larry');
print "Name: ", $thingy->name, $/;
$thingy->age(42);
print "Age: ", $thingy->age, $/;
Or make use of the introspection API:
use MyApp::Thingy;
my $class = MyApp::Thingy->my_class;
my $thingy;
print "Examining object of class ", $class->package, $/;
print "\nConstructors:\n";
for my $ctor ($class->constructors) {
print " o ", $ctor->name, $/;
$thingy = $ctor->call($class->package);
}
print "\nAttributes:\n";
for my $attr ($class->attributes) {
print " o ", $attr->name, " => ", $attr->get($thingy), $/;
if ($attr->authz >= Class::Meta::SET && $attr->type eq 'string') {
$attr->get($thingy, 'hey there!');
print " Changed to: ", $attr->get($thingy), $/;
}
}
print "\nMethods:\n";
for my $meth ($class->methods) {
print " o ", $meth->name, $/;
$meth->call($thingy);
}
DESCRIPTION
Class::Meta provides an interface for automating the creation of Perl classes with
attribute data type validation. It differs from other such modules in that it includes an
introspection API that can be used as a unified interface for all Class::Meta-generated
classes. In this sense, it is an implementation of the "Facade" design pattern.
USAGE
Before we get to the introspection API, let's take a look at how to create classes with
Class::Meta. Unlike many class automation modules for Perl, the classes that Class::Meta
builds do not inherit from Class::Meta. This frees you from any dependencies on the
interfaces that such a base class might compel. For example, you can create whatever
constructors you like, and name them whatever you like.
First of all, you really want to be using Class::Meta::Express to declare your Class::Meta
classes. It provides a much more pleasant class declaration experience than Class::Meta
itself does. But since its functions support many of the same arguments as the declaration
methods described here, it's worth it to skim the notes here, as well. Or if you're just a
masochist and want to use the Class::Meta interface itself, well, read on!
I recommend that you create your Class::Meta classes in a "BEGIN" block. Although this is
not strictly necessary, it helps ensure that the classes you're building are completely
constructed and ready to go by the time compilation has completed. Creating classes with
Class::Meta is easy, using the Class::Meta object oriented interface. Here is an example
of a very simple class:
package MyApp::Dog;
use strict;
use Class::Meta;
use Class::Meta::Types::Perl;
BEGIN {
# Create a Class::Meta object for this class.
my $cm = Class::Meta->new( key => 'dog' );
# Add a constructor.
$cm->add_constructor(
name => 'new',
create => 1,
);
# Add an attribute.
$cm->add_attribute(
name => 'tail',
type => 'scalar',
);
# Add a custom method.
$cm->add_method( name => 'wag' );
$cm->build;
}
sub wag {
my $self = shift;
print "Wagging ", $self->tail;
}
This simple example shows of the construction of all three types of objects supported by
Class::Meta: constructors, attributes, and methods. Here's how it does it:
• First we load Class::Meta and Class::Meta::Types::Perl. The latter module creates data
types that can be used for attributes, including a "scalar" data type.
• Second, we create a Class::Meta object. It's okay to create it within the "BEGIN"
block, as it won't be needed beyond that. All Class::Meta classes have a "key" that
uniquely identifies them across an application. If none is provided, the class name
will be used, instead.
• Next, we create a Class::Meta::Constructor object to describe a constructor method for
the class. The "create" parameter to the "add_constructor()" method tells Class::Meta
to create the constructor named ""new()"".
• Then we call "add_attribute()" to create a single attribute, "tail". This is a simple
scalar attribute, meaning that any scalar value can be stored in it. Class::Meta will
create a Class::Meta::Attribute object that describes this attribute, and will also
shortly create accessor methods for the attribute.
• The "add_method()" method constructs a Class::Meta::Method object to describe any
methods written for the class. In this case, we've told Class::Meta that there will be
a "wag()" method.
• And finally, we tell Class::Meta to build the class. This is the point at which all
constructors and accessor methods will be created in the class. In this case, these
include the "new()" constructor and a "tail()" accessor for the "tail" attribute. And
finally, Class::Meta will install another method, "my_class()". This method will
return a Class::Meta::Class object that describes the class, and provides the complete
introspection API.
Thus, the class the above code creates has this interface:
sub my_class;
sub new;
sub tail;
sub wag;
Data Types
By default, Class::Meta loads no data types. If you attempt to create an attribute without
creating or loading the appropriate data type, you will get an error.
But I didn't want to leave you out in the cold, so I created a whole bunch of data types
to get you started. Any of these will automatically be loaded by Class::Meta if it is used
to create an attribute. They can also be loaded simply by "use"ing the appropriate module.
The modules are:
Class::Meta::Types::Perl
Typical Perl data types.
scalar
Any scalar value.
scalarref
A scalar reference.
array
arrayref
An array reference.
hash
hashref
A hash reference.
code
coderef
closure
A code reference.
Class::Meta::Types::String
string
Attributes of this type must contain a string value. Essentially, this means
anything other than a reference.
Class::Meta::Types::Boolean
boolean
bool
Attributes of this type store a boolean value. Implementation-wise, this means
either a 1 or a 0.
Class::Meta::Types::Numeric
These data types are validated by the functions provided by Data::Types.
whole
A whole number.
integer
An integer.
decimal
A decimal number.
real
A real number.
float
a floating point number.
Other data types may be added in the future. See the individual data type modules for more
information.
Accessors
Class::Meta supports the creation of three different types of attribute accessors: typical
Perl single-method accessors, "affordance" accessors, and "semi-affordance" accessors. The
single accessors are named for their attributes, and typically tend to look like this:
sub tail {
my $self = shift;
return $self->{tail} unless @_;
return $self->{tail} = shift;
}
Although this can be an oversimplification if the data type has associated validation
checks.
Affordance accessors provide at up to two accessors for every attribute: One to set the
value and one to retrieve the value. They tend to look like this:
sub get_tail { shift->{tail} }
sub set_tail { shift->{tail} = shift }
These accessors offer a bit less overhead than the traditional Perl accessors, in that
they don't have to check whether they're called to get or set a value. They also have the
benefit of creating a psychological barrier to misuse. Since traditional Perl accessors
can be created as read-only or write-only accessors, one can't tell just by looking at
them which is the case. The affordance accessors make this point moot, as they make clear
what their purpose is.
Semi-affordance accessors are similar to affordance accessors in that they provide at
least two accessors for every attribute. However, the accessor that fetches the value is
named for the attribute. Thus, they tend to look like this:
sub tail { shift->{tail} }
sub set_tail { shift->{tail} = shift }
To get Class::Meta's data types to create affordance accessors, simply pass the string
"affordance" to them when you load them:
use Class::Meta::Types::Perl 'affordance';
Likewise, to get them to create semi-affordance accessors, pass the string "semi-
affordance":
use Class::Meta::Types::Perl 'semi-affordance';
The boolean data type is the only one that uses a slightly different approach to the
creation of affordance accessors: It creates three of them. Assuming you're creating a
boolean attribute named "alive", it will create these accessors:
sub is_alive { shift->{alive} }
sub set_alive_on { shift->{alive} = 1 }
sub set_alive_off { shift->{alive} = 0 }
Incidentally, I stole the term "affordance" from Damian Conway's "Object Oriented Perl,"
pp 83-84, where he borrows it from Donald Norman.
See Class::Meta::Type for details on creating new data types.
Introspection API
Class::Meta provides four classes the make up the introspection API for
Class::Meta-generated classes. Those classes are:
Class::Meta::Class
Describes the class. Each Class::Meta-generated class has a single constructor object that
can be retrieved by calling a class' "my_class()" class method. Using the
Class::Meta::Class object, you can get access to all of the other objects that describe
the class. The relevant methods are:
constructors
Provides access to all of the Class::Meta::Constructor objects that describe the
class' constructors, and provide indirect access to those constructors.
attributes
Provides access to all of the Class::Meta::Attribute objects that describe the class'
attributes, and provide methods for indirectly getting and setting their values.
methods
Provides access to all of the Class::Meta::Method objects that describe the class'
methods, and provide indirect execution of those constructors.
Class::Meta::Constructor
Describes a class constructor. Typically a class will have only a single constructor, but
there could be more, and client code doesn't necessarily know its name.
Class::Meta::Constructor objects resolve these issues by describing all of the
constructors in a class. The most useful methods are:
name
Returns the name of the constructor, such as "new".
call
Calls the constructor on an object, passing in the arguments passed to "call()"
itself.
Class::Meta::Attribute
Describes a class attribute, including its name and data type. Attribute objects are
perhaps the most useful Class::Meta objects, in that they can provide a great deal of
information about the structure of a class. The most interesting methods are:
name
Returns the name of the attribute.
type
Returns the name of the attribute's data type.
required
Returns true if the attribute is required to have a value.
once
Returns true if the attribute value can be set to a defined value only once.
set Sets the value of an attribute on an object.
get Returns the value of an attribute on an object.
Class::Meta::Method
Describes a method of a class, including its name and context (class vs. instance). The
relevant methods are:
name
The method name.
context
The context of the method indicated by a value corresponding to either
Class::Meta::OBJECT or Class::Meta::CLASS.
call
Calls the method, passing in the arguments passed to "call()" itself.
Consult the documentation of the individual classes for a complete description of their
interfaces.
INTERFACE
Class Methods
default_error_handler
Class::Meta->default_error_handler($code);
my $default_error_handler = Class::Meta->default_error_handler;
Sets the default error handler for Class::Meta classes. If no "error_handler" attribute is
passed to new, then this error handler will be associated with the new class. The default
default error handler uses "Carp::croak()" to handle errors.
Note that if other modules are using Class::Meta that they will use your default error
handler unless you reset the default error handler to its original value before loading
them.
handle_error
Class::Meta->handle_error($err);
Uses the code reference returned by "default_error_handler()" to handle an error. Used
internally Class::Meta classes when no Class::Meta::Class object is available. Probably
not useful outside of Class::Meta unless you're creating your own accessor generation
class. Use the "handle_error()" instance method in Class::Meta::Class, instead.
for_key
my $class = Class::Meta->for_key($key);
Returns the Class::Meta::Class object for a class by its key name. This can be useful in
circumstances where the key has been used to track a class, and you need to get a handle
on that class. With the class package name, you can of course simply call
"$pkg->my_class"; this method is the solution for getting the class object for a class
key.
keys
my @keys = Class::Meta->keys;
Returns the keys for all Class::Meta::Class objects. The order of keys is not guaranteed.
In scalar context, this method returns an array reference containing the keys.
clear
Class::Meta->clear;
Class::Meta->clear($key);
Called without arguments, "clear" will remove all Class::Meta::Class objects from memory.
Called with an argument, "clear" attempts to remove only that key from memory. Calling it
with a non-existent key is a no-op.
In general, you probably won't want to use this method, except perhaps in tests, when you
might need to do funky things with your classes.
Constructors
new
my $cm = Class::Meta->new( key => $key );
Constructs and returns a new Class::Meta object that can then be used to define and build
the complete interface of a class. Many of the supported parameters values will default to
values specified for the most immediate Class::Meta-built parent class, if any. The
supported parameters are:
package
The package that defines the class. Defaults to the package of the code that calls
"new()".
key A key name that uniquely identifies a class within an application. Defaults to the
value of the "package" parameter if not specified.
name
The human name to use for the class. Defaults to the value of "key" with underscores
replaced with spaces and each word capitalized by the "ucfirst" operator. So "foo"
will become "Foo" and "contact_type" will become "Contact Type".
abstract
A boolean indicating whether the class being defined is an abstract class. An abstract
class, also known as a "virtual" class, is not intended to be used directly. No
objects of an abstract class should every be created. Instead, classes that inherit
from an abstract class must be implemented.
default_type
A data type to use for attributes added to the class with no explicit data type. See
"Data Types" for some possible values for this parameter. Inheritable from parent
class.
trust
An array reference of key names or packages that are trusted by the class.
trust => ['Foo::Bar', 'Foo::Bat'],
Trusted packages and the classes that inherit from them can retrieve trusted
attributes and methods of the class. Trusted packages need not be Class::Meta classes.
Trusted classes do not include the declaring class by default, so if you want the
class that declares an attribute to be able to use trusted attribute accessors, be
sure to include it in the list of trusted packages:
trust => [__PACKAGE__, 'Foo::Bar', 'Foo::Bat'],
If you need to trust a single class, you may pass in the key name or package of that
class rather than an array reference:
trust => 'Foo::Bar',
class_class
The name of a class that inherits from Class::Meta::Class to be used to create all of
the class objects for the class. Defaults to Class::Meta::Class. Inheritable from
parent class.
constructor_class
The name of a class that inherits from Class::Meta::Constructor to be used to create
all of the constructor objects for the class. Defaults to Class::Meta::Constructor.
Inheritable from parent class.
attribute_class
The name of a class that inherits from Class::Meta::Attribute to be used to create all
of the attribute objects for the class. Defaults to Class::Meta::Attribute.
Inheritable from parent class.
method_class
The name of a class that inherits from Class::Meta::Method to be used to create all of
the method objects for the class. Defaults to Class::Meta::Method. Inheritable from
parent class.
error_handler
A code reference that will be used to handle errors thrown by the methods created for
the new class. Defaults to the value returned by "Class::Meta->default_error_handler".
Inheritable from parent class.
add_constructor
$cm->add_constructor(
name => 'construct',
create => 1,
);
Creates and returns a Class::Meta::Constructor object that describes a constructor for the
class. The supported parameters are:
name
The name of the constructor. The name must consist of only alphanumeric characters or
"_". Required.
create
When true, Class::Meta::Constructor will automatically create and install a
constructor named for the "name" parameter. Defaults to true unless "code" is passed.
In general you won't need to specify this parameter unless you've written your own
constructor in the package, in which case you'll want to specify "create => 0".
label
A label for the constructor. Generally used for displaying its name in a user
interface. Optional.
desc
A description of the constructor. Possibly useful for displaying help text in a user
interface. Optional.
code
You can implicitly define the constructor in your class by passing a code reference
via the "code" parameter. Once "build()" is called, Kinetic::Meta::Constructor will
install the constructor into the package for which the Class::Meta object was defined,
and with the name specified via the "name" parameter. Note that if the constructor
view is PRIVATE or PROTECTED, the constructor will be wrapped in extra code to
constrain the view. Optional.
view
The visibility of the constructor. The possible values are defined by the following
constants:
Class::Meta::PUBLIC
Can be used by any client.
Class::Meta::PRIVATE
Can only be used by the declaring class.
Class::Meta::TRUSTED
Can only be used by the classes specified by the "trust" parameter to "new()".
Class::Meta::PROTECTED
Can only be used by the declaring class or by classes that inherit from it.
Defaults to Class::Meta::PUBLIC if not defined. You can also use strings aliases to
the above constants, although the constant values will actually be stored in the
Class::Meta::Constructor object, rather than the string. The supported strings are
"PUBLIC", "PRIVATE", "TRUSTED", and "PROTECTED".
caller
A code reference that calls the constructor. Defaults to a code reference that calls a
method with the name provided by the "name" attribute on the class being defined.
If Class::Meta creates the constructor, it will be a simple parameter-list constructor,
wherein attribute values can be passed as a list of attribute-name/value pairs, e.g.:
my $thingy = MyApp::Thingy->new(
name => 'Larry',
age => 32,
);
Required attributes must have a value passed to the constructor, with one exception: You
can pass an optional subroutine reference as the last argument to the constructor. After
all parameter values and default values have been set on the object, but before any
exceptions are thrown for undefined required attributes, the constructor will execute this
subroutine reference, passing in the object being constructed as the sole argument. So,
for example, if "name" is required but, for some reason, could not be set before
constructing the object, you could set it like so:
my $thingy = MyApp::Thingy->new(
age => 32,
sub {
my $thingy = shift;
# age and attributes with default values are already set.
my $name = calculate_name( $thingy );
$thingy->name($name);
},
);
This allows developers to have a scope-limited context in which to work before required
constraints are enforced.
add_attribute
$cm->add_attribute(
name => 'tail',
type => 'scalar',
);
Creates and returns a Class::Meta::Attribute object that describes an attribute of the
class. The supported parameters are:
name
The name of the attribute. The name must consist of only alphanumeric characters or
"_". Required.
type
is The data type of the attribute. See "Data Types" for some possible values for this
parameter. If the type name corresponds to a data type in a package in the
Class::Meta::Types name space, that package will automatically be loaded and
configured with Perl-style accessors, so that the data type can simply be used. If
both "type" and "is" are passed, "is" will be used. Required unless the class was
declared with a "default_type".
required
A boolean value indicating whether the attribute is required to have a value.
Defaults to false.
once
A boolean value indicating whether the attribute can be set to a defined value only
once. Defaults to false.
label
A label for the attribute. Generally used for displaying its name in a user interface.
Optional.
desc
A description of the attribute. Possibly useful for displaying help text in a user
interface. Optional.
view
The visibility of the attribute. See the description of the "view" parameter to
"add_constructor" for a description of its value.
authz
The authorization of the attribute. This value indicates whether it is read-only,
write-only, read/write, or inaccessible. The possible values are defined by the
following constants:
Class::Meta::READ
Class::Meta::WRITE
Class::Meta::RDWR
Class::Meta::NONE
Defaults to Class::Meta::RDWR if not defined. You can also use strings aliases to the
above constants, although the constant values will actually be stored in the
Class::Meta::Attribute object, rather than the string. The supported strings are
"READ", "WRITE", "RDWR", and "NONE".
create
Indicates what type of accessor or accessors are to be created for the attribute.
Class::Meta::GET
Create read-only accessor(s).
Class::Meta::SET
Create write-only accessor(s).
Class::Meta::GETSET
Create read/write accessor(s).
Class::Meta::NONE
Create no accessors.
You can also use strings aliases to the above constants, although the constant values
will actually be stored in the Class::Meta::Attribute object, rather than the string.
The supported strings are "GET", "SET", "GETSET", and "NONE".
If not unspecified, the value of the "create" parameter will correspond to the value
of the "authz" parameter like so:
authz create
------------------
READ => GET
WRITE => SET
RDWR => GETSET
NONE => NONE
The "create" parameter differs from the "authz" parameter in case you've taken it upon
yourself to create some accessors, and therefore don't need Class::Meta to do so. For
example, if you were using standard Perl-style accessors, and needed to do something a
little different by coding your own accessor, you'd specify it like this:
$cm->add_attribute(
name => $name,
type => $type,
authz => Class::Meta::RDWR,
create => Class::Meta::NONE
);
Just be sure that your custom accessor compiles before you call "$cm->build" so that
Class::Meta::Attribute can get a handle on it for its "get()" and/or "set()" methods.
context
The context of the attribute. This indicates whether it's a class attribute or an
object attribute. The possible values are defined by the following constants:
Class::Meta::CLASS
Class::Meta::OBJECT
You can also use strings aliases to the above constants, although the constant values
will actually be stored in the Class::Meta::Attribute object, rather than the string.
The supported strings are "CLASS", and "OBJECT".
default
The default value for the attribute, if any. This may be either a literal value or a
code reference that will be executed to generate a default value.
override
If an attribute being added to a class has the same name as an attribute in a parent
class, Class::Meta will normally throw an exception. However, in some cases you might
want to override an attribute in a parent class to change its properties. In such a
case, pass a true value to the "override" parameter to override the attribute and
avoid the exception.
add_method
$cm->add_method( name => 'wag' );
Creates and returns a Class::Meta::Method object that describes a method of the class. The
supported parameters are:
name
The name of the method. The name must consist of only alphanumeric characters or "_".
label
A label for the method. Generally used for displaying its name in a user interface.
Optional.
desc
A description of the method. Possibly useful for displaying help text in a user
interface. Optional.
view
The visibility of the method. See the description of the "view" parameter to
"add_constructor" for a description of its value. Class::Meta only enforces the "view"
if the "code" parameter is used to define the method body. Otherwise, it's up to the
class implementation itself to do the job.
code
You can implicitly define the method in your class by passing a code reference via the
"code" parameter. Once "build()" is called, Kinetic::Meta::Method will install the
method into the package for which the Class::Meta object was defined, and with the
name specified via the "name" parameter. If the "view" is anything other than PUBLIC,
it will be enforced.
context
The context of the method. This indicates whether it's a class method or an object
method. See the description of the "context" parameter to "add_attribute" for a
description of its value.
caller
A code reference that calls the method. This code reference will be be used by the
"call()" method of Class::Meta::Method to execute the method on behalf of an object.
Defaults to a code reference that calls a method with the name provided by the "name"
attribute on the class being defined.
args
A description of the arguments to the method. This can be anything you like, but I
recommend something like a string for a single argument, an array reference for a list
of arguments, or a hash reference for parameter arguments.
returns
A string describing the return value or values of the method.
Instance Methods
class
my $class = $cm->class;
Returns the instance of the Class::Meta::Class object that will be used to provide the
introspection API for the class being generated.
build
$cm->build;
Builds the class defined by the Class::Meta object, including the "my_class()" class
method, and all requisite constructors and accessors.
JUSTIFICATION
One might argue that there are already too many class automation and parameter validation
modules on CPAN. And one would be right. They range from simple accessor generators, such
as Class::Accessor, to simple parameter validators, such as Params::Validate, to more
comprehensive systems, such as Class::Contract and Class::Tangram. But, naturally, none of
them could do exactly what I needed.
What I needed was an implementation of the "Facade" design pattern. Okay, this isn't a
facade like the "Gang of Four" meant it, but it is in the respect that it creates classes
with a common API so that objects of these classes can all be used identically, calling
the same methods on each. This is done via the implementation of an introspection API. So
the process of creating classes with Class::Meta not only creates attributes and
accessors, but also creates objects that describe those classes. Using these descriptive
objects, client applications can determine what to do with objects of
Class::Meta-generated classes. This is particularly useful for user interface code.
TO DO
• Add support for an "accessor" parameter to "add_attribute()" that will be used for the
accessor instead of generating one.
• Make class attribute accessors behave as they do in Class::Data::Inheritable.
• Modify class attribute accessors so that they are thread safe. This will involve
sharing the attributes across threads, and locking them before changing their values.
If they've also been made to behave as they do in Class::Data::Inheritable, we'll have
to figure out a way to make it so that newly generated accessors for subclasses are
shared between threads, too. This may not be easy.
SUPPORT
This module is stored in an open GitHub repository <http://github.com/theory/class-meta/>.
Feel free to fork and contribute!
Please file bug reports via GitHub Issues <http://github.com/theory/class-meta/issues/> or
by sending mail to bug-Class-Meta@rt.cpan.org <mailto:bug-Class-Meta@rt.cpan.org>.
AUTHOR
David E. Wheeler <david@justatheory.com>
SEE ALSO
First of all, use Class::Meta::Express instead of Class::Meta to declare your classes. I
hope I've made that clear enough by now.
Other classes of interest within the Class::Meta distribution include:
Class::Meta::Class
Class::Meta::Constructor
Class::Meta::Attribute
Class::Meta::Method
Class::Meta::Type
Class::Meta::Types::Perl
Class::Meta::Types::String
Class::Meta::Types::Boolean
Class::Meta::Types::Numeric
For comparative purposes, you might also want to check out these fine modules:
Class::Accessor
Accessor and constructor automation.
Params::Validate
Parameter validation.
Class::Contract
Design by contract.
Class::Tangram
Accessor automation and data validation for Tangram applications.
Class::Maker
An ambitious yet under-documented module that also manages accessor and constructor
generation, data validation, and provides a reflection API. It also supports
serialization.
Class::MOP
Stevan Little's application of Perl 6 meta classes to Perl 5.
Moose
"It's the new camel." Another extension of the Perl 5 object system, built on
Class::MOP.
COPYRIGHT AND LICENSE
Copyright (c) 2002-2011, David E. Wheeler. Some Rights Reserved.
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.