NAME
    Class::InsideOut - a safe, simple inside-out object construction kit

VERSION
    This documentation refers to version 1.0301

SYNOPSIS
      package My::Class;
 
      use Class::InsideOut qw( public private register id );
 
      public     name => my %name;       # accessor: name()
      private    age  => my %age;        # no accessor
 
      sub new { register( shift ) }
 
      sub greeting {
        my $self = shift;
        return "Hello, my name is $name{ id $self }";
      }

DESCRIPTION
    This is a simple, safe and streamlined toolkit for building inside-out
    objects. Unlike most other inside-out object building modules already on
    CPAN, this module aims for minimalism and robustness:

    *   Does not require derived classes to subclass it

    *   Uses no source filters, attributes or "CHECK" blocks

    *   Supports any underlying object type including black-box inheritance

    *   Does not leak memory on object destruction

    *   Overloading-safe

    *   Thread-safe for Perl 5.8 or better

    *   "mod_perl" compatible

    *   Makes no assumption about inheritance or initializer needs

    It provides the minimal support necessary for creating safe inside-out
    objects and generating flexible accessors.

  Additional documentation
    *   Class::InsideOut::Manual::About -- Guide to the inside-out
        technique, the "Class::InsideOut" philosophy, and other inside-out
        implementations

    *   Class::InsideOut::Manual::Advanced -- Advanced topics including
        customizing accessors, black-box inheritance, serialization and
        thread safety

USAGE
  Importing "Class::InsideOut"
    "Class::InsideOut" automatically imports several critical methods into
    the calling package, including "DESTROY" and support methods for
    serializing objects with "Storable". These methods are intimately tied
    to correct functioning of inside-out objects and will always be imported
    regardless of whether additional functions are requested.

    Additional functions may be imported as usual by including them as
    arguments to "use". For example:

      use Class::InsideOut qw( register public );
 
      public name => my %name;
 
      sub new { register( shift ) }

    As a shortcut, "Class::InsideOut" supports two tags for importing sets
    of functions:

    *   ":std" provides "id", "private", "public" and "register"

    *   ":all" imports all functions (including an optional constructor)

    Note: Automatic imports can be bypassed via "require" or by passing an
    empty list to "use Class::InsideOut". There is almost no circumstance in
    which this is a good idea.

  Object properties and accessors
    Object properties are declared with the "public" and "private"
    functions. They must be passed a label and the lexical hash that will be
    used to store object properties:

      public name => my %name;
      private age => my %age;

    Properties for an object are accessed through an index into the lexical
    hash based on the memory address of the object. This memory address
    *must* be obtained via "Scalar::Util::refaddr". The alias "id" may be
    imported for brevity.

      $name{ refaddr $self } = "James";
      $age { id      $self } = 32;

    Tip: since "refaddr" and "id" are function calls, it may be efficient to
    store the value once at the beginning of a method, particularly if it is
    being called repeatedly, e.g. within a loop.

    Object properties declared with "public" will have an accessor created
    with the same name as the label. If the accessor is passed an argument,
    the property will be set to the argument. The accessor always returns
    the value of the property.

      # Outside the class
      $person = My::Class->new;
      $person->name( "Larry" );

    Property accessors may also be hand-written by declaring the property
    "private" and writing whatever style of accessor is desired. For
    example:

      sub age     { $age{ id $_[0] } }
      sub set_age { $age{ id $_[0] } = $_[1] }

    Hand-written accessors will be very slightly faster as generated
    accessors hold a reference to the property hash rather than accessing
    the property hash directly.

  Object construction
    "Class::InsideOut" provides no default constructor method as there are
    many possible ways of constructing an inside-out object. This avoids
    constraining users to any particular object initialization or superclass
    initialization methodology.

    By using the memory address of the object as the index for properties,
    *any* type of reference may be used as the basis for an inside-out
    object with "Class::InsideOut".

      sub new {
        my $class = shift;
 
        my $self = \( my $scalar );    # anonymous scalar
      # my $self = {};                 # anonymous hash
      # my $self = [];                 # anonymous array
      # open my $self, "<", $filename; # filehandle reference
 
        bless $self, $class;
        register( $self );
      }

    However, to ensure that the inside-out object is thread-safe, the
    "register" function *must* be called on the newly created object. The
    "register" function may also be called with just the class name for the
    common case of blessing an anonymous scalar.

      register( $class ); # same as register( bless \(my $s), $class )

    As a convenience, "Class::InsideOut" provides an optional "new"
    constructor for simple objects.

    A more advanced technique for object construction uses another object,
    usually a superclass object, as the object reference. See "black-box
    inheritance" in Class::InsideOut::Manual::Advanced.

  Object destruction
    "Class::InsideOut" automatically exports a special "DESTROY" function.
    This function cleans up object property memory for all declared
    properties the class and for all "Class::InsideOut" based classes in the
    @ISA array to avoid memory leaks or data collision.

    Additionally, if a user-supplied "DEMOLISH" function is available in the
    same package, it will be called with the object being destroyed as its
    argument. "DEMOLISH" can be used for custom destruction behavior such as
    updating class properties, closing sockets or closing database
    connections. Object properties will not be deleted until after
    "DEMOLISH" returns.

      # Sample DEMOLISH: Count objects demolished (for whatever reason)
 
      my $objects_destroyed;
 
      sub DEMOLISH {
        $objects_destroyed++;
      }

    "DEMOLISH" will only be called if it exists for an object's actual
    class. "DEMOLISH" will not be inherited and "DEMOLISH" will not be
    called automatically for any superclasses.

    "DEMOLISH" should manage any necessary calls to superclass "DEMOLISH"
    methods. As with "new", implementation details are left to the user
    based on the user's approach to object inheritance. Depending on how the
    inheritance chain is constructed and how "DEMOLISH" is being used, users
    may wish to entirely override superclass "DEMOLISH" methods, rely upon
    "SUPER::DEMOLISH", or may prefer to walk the entire @ISA tree:

      use Class::ISA;
 
      sub DEMOLISH {
        my $self = shift;
        # class specific demolish actions
 
        # DEMOLISH for all parent classes, but only once
        my @parents = Class::ISA::super_path( __PACKAGE__ );
        my %called;
        for my $p ( @parents  ) {
          my $demolish = $p->can('DEMOLISH');
          $demolish->($self) if not $called{ $demolish }++;
        }
      }

FUNCTIONS
  "id"
      $name{ id $object } = "Larry";

    This is a shorter, mnemonic alias for "Scalar::Util::refaddr". It
    returns the memory address of an object (just like "refaddr") as the
    index to access the properties of an inside-out object.

  "new"
      My::Class->new( name => "Larry", age => 42 );

    This simplistic constructor is provided as a convenience and is only
    exported on request. When called as a class method, it returns a blessed
    anonymous scalar. Arguments will be used to initialize all matching
    inside-out class properties in the @ISA tree. The argument may be a hash
    or hash reference.

  "options"
      Class::InsideOut::options( \%new_options );
      %current_options = Class::InsideOut::options();

    The "options" function sets default options for use with all subsquent
    property definitions for the calling package. If called without
    arguments, this function will return the options currently in effect.
    When called with a hash reference of options, these will be joined with
    the existing defaults, overriding any options of the same name.

  "private"
      private weight => my %weight;
      private haircolor => my %hair_color, { %options };

    This is an alias to "property" that also sets the privacy option to
    'private'. It will override default options or options passed as an
    argument.

  "property"
      property name => my %name;
      property rank => my %rank, { %options };

    Declares an inside-out property. Two arguments are required and a third
    is optional. The first is a label for the property; this label will be
    used for introspection and generating accessors and thus must be a valid
    perl identifier. The second argument must be the lexical hash that will
    be used to store data for that property. Note that the "my" keyword can
    be included as part of the argument rather than as a separate statement.
    The property will be tracked for memory cleanup during object
    destruction and for proper thread-safety.

    If a third, optional argument is provided, it must be a reference to a
    hash of options that will be applied to the property and will override
    any default options that have been set.

  "public"
      public height => my %height;
      public age => my %age, { %options };

    This is an alias to "property" that also sets the privacy option to
    'public'. It will override default options or options passed as an
    argument.

  "register"
      register( bless( $object, $class ) ); # register the object 
      register( $reference, $class );       # automatic bless 
      register( $class );                   # automatic blessed scalar

    Registers objects for thread-safety. This should be called as part of a
    constructor on a object blessed into the current package. Returns the
    resulting object. When called with only a class name, "register" will
    bless an anonymous scalar reference into the given class. When called
    with both a reference and a class name, "register" will bless the
    reference into the class.

OPTIONS
    Options customize how properties are generated. Options may be set as a
    default with the "options" function or passed as a hash reference to
    "public", "private" or "property".

    Valid options include:

  "privacy"
      property rank => my %rank, { privacy => 'public' };
      property serial => my %serial, { privacy => 'private' };

    If the *privacy* option is set to *public*, an accessor will be created
    with the same name as the label. If the accessor is passed an argument,
    the property will be set to the argument. The accessor always returns
    the value of the property.

  "get_hook"
      public list => my %list, {
          get_hook => sub { @$_ }
      };

    Defines an accessor hook for when values are retrieved. $_ is locally
    aliased to the property value for the object. *The return value of the
    hook is passed through as the return value of the accessor.* See
    "Customizing Accessors" in Class::InsideOut::Manual::Advanced for
    details.

  "set_hook"
      public age => my %age, {
         set_hook => sub { /^\d+$/ or die "must be an integer" }
      };

    Defines an accessor hook for when values are set. The hook subroutine
    receives the entire argument list. $_ is locally aliased to the first
    argument for convenience. The property receives the value of $_. See
    "Customizing Accessors" in Class::InsideOut::Manual::Advanced for
    details.

SEE ALSO
    Programmers seeking a more full-featured approach to inside-out objects
    are encouraged to explore Object::InsideOut. Other implementations are
    also noted in Class::InsideOut::Manual::About.

ROADMAP
    Features slated for after the 1.0 release include:

    *   Adding support for Data::Dump::Streamer serialization hooks

    *   Adding additional accessor styles (e.g. get_name()/set_name())

    *   Further documentation revisions and clarification

BUGS
    Please report bugs or feature requests using the CPAN Request Tracker:
    <http://rt.cpan.org/Public/Dist/Display.html?Name=Class-InsideOut>

    When submitting a bug or request, please include a test-file or a patch
    to an existing test-file that illustrates the bug or desired feature.

AUTHOR
    David A. Golden (DAGOLDEN)

    dagolden@cpan.org

    http://dagolden.com/

COPYRIGHT AND LICENSE
    Copyright (c) 2006 by David A. Golden

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

    The full text of the license can be found in the LICENSE file included
    with this module.

DISCLAIMER OF WARRANTY
    BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
    FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
    OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
    PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
    EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
    ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
    YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
    NECESSARY SERVICING, REPAIR, OR CORRECTION.

    IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
    WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
    REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
    TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
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    SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
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