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

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 v5.24.1			  2005-04-27		      Class::Loader(3)

NAME | VERSION | SYNOPSIS | DESCRIPTION | METHODS | SEE ALSO | AUTHOR | LICENSE

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