NAME
   Class::Autouse - Run-time load a class the first time you call a method
   in it.

SYNOPSIS
     # Debugging (if you go that way) must be set before the first use
     BEGIN {
         $Class::Autouse::DEBUG = 1;
     }

     # Load a class on method call
     use Class::Autouse;
     Class::Autouse->autouse( 'CGI' );
     print CGI->b('Wow!');

     # Use as a pragma
     use Class::Autouse qw{CGI};

     # Turn on developer mode
     use Class::Autouse qw{:devel};

     # Turn on the Super Loader
     use Class::Autouse qw{:superloader};

     # Disable module-existance check, and thus one additional 'stat'
     # per module, at autouse-time if loading modules off a remote
     # network drive such as NFS or SMB.
     use Class::Autouse qw{:nostat};

DESCRIPTION
   "Class::Autouse" allows you to specify a class the will only load when a
   method of that class is called. For large classes that might not be used
   during the running of a program, such as Date::Manip, this can save you
   large amounts of memory, and decrease the script load time a great deal.

 Class, not Module
   The terminology "class loading" instead of "module loading" is used
   intentionally. Modules will only be loaded if they are acting as a
   class.

   That is, they will only be loaded during a Class->method call. If you
   try to use a subroutine directly, say with "Class::method()", the class
   will not be loaded and a fatal error will mostly likely occur.

   This limitation is made to allow more powerfull features in other areas,
   because the module can focus on just loading the modules, and not have
   to deal with importing.

   And really, if you are doing OO Perl, you should be avoiding importing
   wherever possible.

 Use as a pragma
   Class::Autouse can be used as a pragma, specifying a list of classes to
   load as the arguments. For example

      use Class::Autouse qw{CGI Data::Manip This::That};

   is equivalent to

      use Class::Autouse;
      Class::Autouse->autouse( 'CGI'         );
      Class::Autouse->autouse( 'Data::Manip' );
      Class::Autouse->autouse( 'This::That'  );

 Developer Mode
   "Class::Autouse" features a developer mode. In developer mode, classes
   are loaded immediately, just like they would be with a normal 'use'
   statement (although the import sub isn't called).

   This allows error checking to be done while developing, at the expense
   of a larger memory overhead. Developer mode is turned on either with the
   "devel" method, or using :devel in any of the pragma arguments. For
   example, this would load CGI.pm immediately

       use Class::Autouse qw{:devel CGI};

   While developer mode is roughly equivalent to just using a normal use
   command, for a large number of modules it lets you use autoloading
   notation, and just comment or uncomment a single line to turn developer
   mode on or off. You can leave it on during development, and turn it off
   for speed reasons when deploying.

 No-Stat Mode
   For situations where a module exists on a remote disk or another
   relatively expensive location, you can call "Class::Autouse" with the
   :nostat param to disable initial file existance checking at hook time.

     # Disable autoload-time file existance checking
     use Class::Autouse qw{:nostat};

 Super Loader Mode
   Turning on the "Class::Autouse" super loader allows you to automatically
   load ANY class without specifying it first. Thus, the following will
   work and is completely legal.

       use Class::Autouse qw{:superloader};

       print CGI->b('Wow!');

   The super loader can be turned on with either the
   "Class::Autouse->"superloader> method, or the ":superloader" pragma
   argument.

   Please note that unlike the normal one-at-a-time autoloading, the
   super-loader makes global changes, and so is not completely
   self-contained.

   It has the potential to cause unintended effects at a distance. If you
   encounter unusual behaviour, revert to autousing one-at-a-time, or use
   the recursive loading.

   Use of the Super Loader is highly discouraged for widely distributed
   public applications or modules unless unavoidable. Do not use just to be
   lazy and save a few lines of code.

 Recursive Loading
   As an alternative to the super loader, the "autouse_recursive" and
   "load_recursive" methods can be used to autouse or load an entire tree
   of classes.

   For example, the following would give you access to all the URI related
   classes installed on the machine.

       Class::Autouse->autouse_recursive( 'URI' );

   Please note that the loadings will only occur down a single branch of
   the include path, whichever the top class is located in.

 mod_perl
   The mechanism that "Class::Autouse" uses is not compatible with
   mod_perl. In particular with reloader modules like Apache::Reload.
   "Class::Autouse" detects the presence of mod_perl and acts as normal,
   but will always load all classes immediately, equivalent to having
   developer mode enabled.

   This is actually beneficial, as under mod_perl classes should be
   preloaded in the parent mod_perl process anyway, to prevent them having
   to be loaded by the Apache child classes. It also saves HUGE amounts of
   memory.

 prefork
   As for mod_perl, "Class::Autouse" is compatible with the prefork module,
   and all modules autoloaded will be loaded before forking correctly, when
   requested by prefork.

 The Internal Debugger
   Class::Autouse provides an internal debugger, which can be used to debug
   any weird edge cases you might encounter when using it.

   If the $Class::Autouse::DEBUG variable is true when "Class::Autouse" is
   first loaded, debugging will be compiled in. This debugging prints
   output like the following to STDOUT.

    Class::Autouse::autouse_recursive( 'Foo' )
     Class::Autouse::_recursive( 'Foo', 'load' )
      Class::Autouse::load( 'Foo' )
      Class::Autouse::_child_classes( 'Foo' )
      Class::Autouse::load( 'Foo::Bar' )
       Class::Autouse::_file_exists( 'Foo/Bar.pm' )
       Class::Autouse::load -> Loading in Foo/Bar.pm
      Class::Autouse::load( 'Foo::More' )
       etc...

   Please note that because this is optimised out if not used, you can no
   longer (since 1.20) enable debugging at run-time. This decision was made
   to remove a large number of unneeded branching and speed up loading.

METHODS
 autouse $class, ...
   The autouse method sets one or more classes to be loaded as required.

 load $class
   The load method loads one or more classes into memory. This is
   functionally equivalent to using require to load the class list in,
   except that load will detect and remove the autoloading hook from a
   previously autoused class, whereas as use effectively ignore the class,
   and not load it.

 devel
   The devel method sets development mode on (argument of 1) or off
   (argument of 0).

   If any classes have previously been autouse'd and not loaded when this
   method is called, they will be loaded immediately.

 superloader
   The superloader method turns on the super loader.

   Please note that once you have turned the superloader on, it cannot be
   turned off. This is due to code that might be relying on it being there
   not being able to autoload its classes when another piece of code
   decides they don't want it any more, and turns the superloader off.

 class_exists $class
   Handy method when doing the sort of jobs that "Class::Autouse" does.
   Given a class name, it will return true if the class can be loaded (
   i.e. in @INC ), false if the class can't be loaded, and undef if the
   class name is invalid.

   Note that this does not actually load the class, just tests to see if it
   can be loaded. Loading can still fail. For a more comprehensive set of
   methods of this nature, see Class::Inspector.

 autouse_recursive $class
   The same as the "autouse" method, but autouses recursively.

 load_recursive $class
   The same as the "load" method, but loads recursively. Great for checking
   that a large class tree that might not always be loaded will load
   correctly.

SUPPORT
   Bugs should be always be reported via the CPAN bug tracker at

   <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Class-Autouse>

   For other issues, or commercial enhancement or support, contact the
   author.

AUTHORS
   Adam Kennedy (Creator and Maintainer), <http://ali.as/>, [email protected]

   Rob Napier (No longer involved), [email protected]

SEE ALSO
   autoload, autoclass

COPYRIGHT
   Copyright (c) 2002 - 2006 Adam Kennedy.

   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.

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