NAME

       Class::Loader - Load modules and create objects on demand.

VERSION

           $Revision: 2.2 $
           $Date: 2001/07/18 20:21:39 $

SYNOPSIS

           package Web::Server;
           use Class::Loader;
           @ISA = qw(Class::Loader);

           $self->_load( 'Content_Handler', {
                                    Module => "Filter::URL",
                               Constructor => "new",
                                      Args => [ ],
                                }
                       );

DESCRIPTION

       Certain applications like to defer the decision to use a particular module till runtime.
       This is possible in perl, and is a useful trick in situations where the type of data is
       not known at compile time and the application doesn't wish to pre-compile modules to
       handle all types of data it can work with. Loading modules at runtime can also provide
       flexible interfaces for perl modules. Modules can let the programmer decide what modules
       will be used by it instead of hard-coding their names.

       Class::Loader is an inheritable class that provides a method, _load(), to load a module
       from disk and construct an object by calling its constructor. It also provides a way to
       map modules names and associated metadata with symbolic names that can be used in place of
       module names at _load().

METHODS

       new()
           A basic constructor. You can use this to create an object of Class::Loader, in case
           you don't want to inherit Class::Loader.

       _load()
           _load() loads a module and calls its constructor. It returns the newly constructed
           object on success or a non-true value on failure. The first argument can be the name
           of the key in which the returned object is stored. This argument is optional. The
           second (or the first) argument is a hash which can take the following keys:

           Module
               This is name of the class to load. (It is not the module's filename.)

           Name
               Symbolic name of the module defined with _storemap(). Either one of Module or Name
               keys must be present in a call to _load().

           Constructor
               Name of the Module constructor. Defaults to "new".

           Args
               A reference to the list of arguments for the constructor. _load() calls the
               constructor with this list. If no Args are present, _load() will call the
               constructor without any arguments.

           CPAN
               If the Module is not installed on the local system, _load() can fetch & install it
               from CPAN provided the CPAN key is present. This functionality assumes
               availability of a pre-configured CPAN shell.

       _storemap()
           Class::Loader maintains a class table that maps symbolic names to parameters accepted
           by _load(). It takes a hash as argument whose keys are symbolic names and value are
           hash references that contain a set of _load() arguments. Here's an example:

               $self->_storemap ( "URL" => { Module => "Filter::URL",
                                             Constructor => "foo",
                                             Args => [qw(bar baz)],
                                           }
                                );

               # time passes...

               $self->{handler} = $self->_load ( Name => 'URL' );

       _retrmap()
           _retrmap() returns the entire map stored with Class::Loader. Class::Loader maintains
           separate maps for different classes, and _retrmap() returns the map valid in the
           caller class.

SEE ALSO

       AnyLoader(3)

AUTHOR

       Vipul Ved Prakash, <mail@vipul.net>

LICENSE

       Copyright (c) 2001, Vipul Ved Prakash. All rights reserved. This code is free software;
       you can redistribute it and/or modify it under the same terms as Perl itself.