NAME

       Class::Meta::Attribute - Class::Meta class attribute introspection

SYNOPSIS

         # Assuming MyApp::Thingy was generated by Class::Meta.
         my $class = MyApp::Thingy->my_class;
         my $thingy = MyApp::Thingy->new;

         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) $/;
             }
         }

DESCRIPTION

       An object of this class describes an attribute of a class created by Class::Meta. It
       includes meta data such as the name of the attribute, its data type, its accessibility,
       and whether or not a value is required. It also provides methods to easily get and set the
       value of the attribute for a given instance of the class.

       Class::Meta::Attribute objects are created by Class::Meta; they are never instantiated
       directly in client code. To access the attribute objects for a Class::Meta-generated
       class, simply call its "my_class()" method to retrieve its Class::Meta::Class object, and
       then call the "attributes()" method on the Class::Meta::Class object.

INTERFACE

   Constructors
       new

       A protected method for constructing a Class::Meta::Attribute object. Do not call this
       method directly; Call the "add_attribute()" method on a Class::Meta object, instead.

   Instance Methods
       name

         my $name = $attr->name;

       Returns the name of the attribute.

       type

         my $type = $attr->type;

       Returns the name of the attribute's data type. Typical values are "scalar", "string", and
       "boolean". See Class::Meta for a complete list.

       is

         if ($attr->is('string')) {
             # ...
         }

       A convenience method for "$attr->type eq $type".

       desc

         my $desc = $attr->desc;

       Returns a description of the attribute.

       label

         my $label = $attr->label;

       Returns a label for the attribute, suitable for use in a user interface. It is
       distinguished from the attribute name, which functions to name the accessor methods for
       the attribute.

       required

         my $req = $attr->required;

       Indicates if the attribute is required to have a value.

       once

         my $once = $attr->once;

       Indicates whether an attribute value can be set to a defined value only once.

       package

         my $package = $attr->package;

       Returns the package name of the class that attribute is associated with.

       view

         my $view = $attr->view;

       Returns the view of the attribute, reflecting its visibility. The possible values are
       defined by the following constants:

       Class::Meta::PUBLIC
       Class::Meta::PRIVATE
       Class::Meta::TRUSTED
       Class::Meta::PROTECTED

       context

         my $context = $attr->context;

       Returns the context of the attribute, essentially whether it is a class or object
       attribute. The possible values are defined by the following constants:

       Class::Meta::CLASS
       Class::Meta::OBJECT

       authz

         my $authz = $attr->authz;

       Returns the authorization for the attribute, which determines whether it can be read or
       changed. The possible values are defined by the following constants:

       Class::Meta::READ
       Class::Meta::WRITE
       Class::Meta::RDWR
       Class::Meta::NONE

       class

         my $class = $attr->class;

       Returns the Class::Meta::Class object that this attribute is associated with. Note that
       this object will always represent the class in which the attribute is defined, and not any
       of its subclasses.

       default

         my $default = $attr->default;

       Returns the default value for a new instance of this attribute. Since the default value
       can be determined dynamically, the value returned by "default()" may change on subsequent
       calls. It all depends on what was passed for the "default" parameter in the call to
       "add_attribute()" on the Class::Meta object that generated the class.

       get

         my $value = $attr->get($thingy);

       This method calls the "get" accessor method on the object passed as the sole argument and
       returns the value of the attribute for that object. Note that it uses a "goto" to execute
       the accessor, so the call to "set()" itself will not appear in a call stack trace.

       set

         $attr->set($thingy, $new_value);

       This method calls the "set" accessor method on the object passed as the first argument and
       passes any remaining arguments to assign a new value to the attribute for that object.
       Note that it uses a "goto" to execute the accessor, so the call to "set()" itself will not
       appear in a call stack trace.

       build

         $attr->build($class);

       This is a protected method, designed to be called only by the Class::Meta class or a
       subclass of Class::Meta. It takes a single argument, the Class::Meta::Class object for the
       class in which the attribute was defined, and generates attribute accessors by calling out
       to the "make_attr_get()" and "make_attr_set()" methods of Class::Meta::Type as appropriate
       for the Class::Meta::Attribute object.

       Although you should never call this method directly, subclasses of
       Class::Meta::Constructor may need to override its behavior.

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

       Other classes of interest within the Class::Meta distribution include:

       Class::Meta
       Class::Meta::Class
       Class::Meta::Method
       Class::Meta::Constructor
       Class::Meta::Type

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.