NAME
Class::Autouse - Run-time class loading on first method call
SYNOPSIS
# 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 debugging
use Class::Autouse qw{:debug};
# Turn on developer mode
use Class::Autouse qw{:devel};
# Turn on the Super Loader
use Class::Autouse qw{:superloader};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.
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' );The Internal Debugger
Given the :debug pragma argument, Class::Autouse will dump detailed internal call information. This can be usefull when an error has occurred that may be a little difficult to debug, and some more inforamtion about when the problem has actually occurred is required. Debug messages are written to STDOUT, and will look something like
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...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 that is relatively expensive to get to, you can call Class::Autouse with the :nostat param to disable initial file existance checking at hook time.
Super Loader
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.
Recursion
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.
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 do use a subroutine directly, say with Class::method(), the class will not be loaded. 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.
mod_perl
The methods that Class::Autouse uses are 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.
METHODS
autouse $class
The autouse method sets the class 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)
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.
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 (Maintainer), http://ali.as/, cpan@ali.as
Rob Napier (No longer involved), rnapier@employees.org
SEE ALSO
COPYRIGHT
Copyright (c) 2002 - 2005 Adam Kennedy. All rights reserved.
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.