Hash::Wrap

This module provides constructors which create light-weight objects from
existing hashes, allowing access to hash elements via methods (and thus
avoiding typos). Attempting to access a non-existent element via a
method will result in an exception.

Hash elements may be added to or deleted from the object after
instantiation using the standard Perl hash operations, and changes will
be reflected in the object's methods. For example,

   $obj = wrap_hash( { a => 1, b => 2 );
   $obj->c; # throws exception
   $obj->{c} = 3;
   $obj->c; # returns 3
   delete $obj->{c};
   $obj->c; # throws exception

To prevent modification of the hash, consider using the lock routines in
Hash::Util on the object.

The methods act as both accessors and setters, e.g.

  $obj = wrap_hash( { a => 1 } );
  print $obj->a; # 1
  $obj->a( 3 );
  print $obj->a; # 3

Only hash keys which are legal method names will be accessible via
object methods.

  Object construction and constructor customization

By default "Hash::Wrap" exports a "wrap_hash" subroutine which, given a
hashref, blesses it directly into the Hash::Wrap::Class class.

The constructor may be customized to change which class the object is
instantiated from, and how it is constructed from the data. For example,

  use Hash::Wrap
    { -as => 'return_cloned_object', -clone => 1 };

will create a constructor which clones the passed hash and is imported
as "return_cloned_object". To import it under the original name,
"wrap_hash", leave out the "-as" option.

The following options are available to customize the constructor.

"-as" => *subroutine name*
    This is optional, and imports the constructor with the given name.
    If not specified, it defaults to "wrap_hash".

"-class" => *class name*
    The object will be blessed into the specified class. If the class
    should be created on the fly, specify the "-create" option. See
    "Object Classes" for what is expected of the object classes. This
    defaults to "Hash::Wrap::Class".

"-create" => *boolean*
    If true, and "-class" is specified, a class with the given name will
    be created.

"-copy" => *boolean*
    If true, the object will store the data in a *shallow* copy of the
    hash. By default, the object uses the hash directly.

"-clone" => *boolean* | *coderef*
    Store the data in a deep copy of the hash. if *true*, "dclone" in
    Storable is used. If a coderef, it will be called as

       $clone = coderef->( $hash )

    By default, the object uses the hash directly.

  Object Classes

An object class has the following properties:

*   The class must be a subclass of "Hash::Wrap::Base".

*   The class typically does not provide any methods, as they would mask
    a hash key of the same name.

*   The class need not have a constructor. If it does, it is passed a
    hashref which it should bless as the actual object. For example:

      package My::Result;
      use parent 'Hash::Wrap::Base';

      sub new {
        my  ( $class, $hash ) = @_;
        return bless $hash, $class;
      }

    This excludes having a hash key named "new".

"Hash::Wrap::Base" provides an empty "DESTROY" method, a "can" method,
and an "AUTOLOAD" method. They will mask hash keys with the same names.

INSTALLATION

This is a Perl module distribution. It should be installed with whichever
tool you use to manage your installation of Perl, e.g. any of

  cpanm .
  cpan  .
  cpanp -i .

Consult http://www.cpan.org/modules/INSTALL.html for further instruction.
Should you wish to install this module manually, the procedure is

  perl Makefile.PL
  make
  make test
  make install

COPYRIGHT AND LICENSE

This software is Copyright (c) 2017 by Smithsonian Astrophysical
Observatory.

This is free software, licensed under:

  The GNU General Public License, Version 3, June 2007
