Class::Loader(3pm)					User Contributed Perl Documentation					Class::Loader(3pm)

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.

perl v5.10.1							    2005-04-27							Class::Loader(3pm)