Class::Autouse man page on Pidora

Man page or keyword search:  
man Server   31170 pages
apropos Keyword Search (all sections)
Output format
Pidora logo
[printable version]

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

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

SYNOPSIS
	   ##################################################################
	   # SAFE FEATURES

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

	   # Turn on developer mode (always load immediately)
	   use Class::Autouse qw{:devel};

	   # 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};

	   # Use a whole module tree
	   Class::Autouse->autouse_recursive('Acme');

	   # 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.
	   # (See below for other performance optimizations.)
	   use Class::Autouse qw{:nostat};

	   ##################################################################
	   # UNSAFE FEATURES

	   # Turn on the Super Loader (load all classes on demand)
	   use Class::Autouse qw{:superloader};

	   # Autouse classes matching a given regular expression
	   use Class::Autouse qr/::Test$/;

	   # Install a class generator (instead of overriding UNIVERSAL::AUTOLOAD)
	   # (See below for a detailed example)
	   use Class::Autouse \&my_class_generator;

	   # Add a manual callback to UNIVERSAL::AUTOLOAD for syntactic sugar
	   Class::Autouse->sugar(\&my_magic);

DESCRIPTION
       Class::Autouse is a runtime class loader that allows you to specify
       classes that will only load when a method of that class is called.

       For large classes or class trees 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::Autouse also provides a number of "unsafe" features for runtime
       generation of classes and implementation of syntactic sugar. These
       features make use of (evil) UNIVERSAL::AUTOLOAD hooking, and are
       implemented in this class because these hooks can only be done by a one
       module, and Class::Autouse serves as a useful place to centralise this
       kind of evil :)

   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 we 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.

   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.

   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.

   Loading with Regular Expressions
       As another alternative to the superloader and recursive loading, a
       compiled regular expression (qr//) can be supplied as a loader.	Note
       that this loader implements UNIVERSAL::AUTOLOAD, and has the same side
       effects as the superloader.

   Registering a Callback for Dynamic Class Creation
       If none of the above are sufficient, a CODE reference can be given to
       Class::Autouse.	Any attempt to call a method on a missing class will
       launch each registered callback until one returns true.

       Since overriding UNIVERSAL::AUTOLOAD can be done only once in a given
       Perl application, this feature allows UNIVERSAL::AUTOLOAD to be shared.
       Please use this instead of implementing your own UNIVERSAL::AUTOLOAD.

       See the warnings under the "Super Loader Module" above which apply to
       all of the features which override UNIVERSAL::AUTOLOAD.

       It is up to the callback to define the class, the details of which are
       beyond the scope of this document.   See the example below for a quick
       reference:

       Callback Example

       Any use of a class like Foo::Wrapper autogenerates that class as a
       proxy around Foo.

	   use Class::Autouse sub {
	       my ($class) = @_;
	       if ($class =~ /(^.*)::Wrapper/) {
		   my $wrapped_class = $1;
		   eval "package $class; use Class::AutoloadCAN;";
		   die $@ if $@;
		   no strict 'refs';
		   *{$class . '::new' } = sub {
		       my $class = shift;
		       my $proxy = $wrapped_class->new(@_);
		       my $self = bless({proxy => $proxy},$class);
		       return $self;
		   };
		   *{$class . '::CAN' } = sub {
		       my ($obj,$method) = @_;
		       my $delegate = $wrapped_class->can($method);
		       return unless $delegate;
		       my $delegator = sub {
			   my $self = shift;
			   if (ref($self)) {
			       return $self->{proxy}->$method(@_);
			   }
			   else {
			       return $wrapped_class->$method(@_);
			   }
		       };
		       return *{ $class . '::' . $method } = $delegator;
		   };

		   return 1;
	       }
	       return;
	   };

	   package Foo;
	   sub new { my $class = shift; bless({@_},$class); }
	   sub class_method { 123 }
	   sub instance_method {
	       my ($self,$v) = @_;
	       return $v * $self->some_property
	   }
	   sub some_property { shift->{some_property} }

	   package main;
	   my $x = Foo::Wrapper->new(
	       some_property => 111,
	   );
	   print $x->some_property,"\n";
	   print $x->instance_method(5),"\n";
	   print Foo::Wrapper->class_method,"\n";

   sugar
       This method is provided to support "syntactic sugar": allowing the
       developer to put things into Perl which do not look like regular Perl.
       There are several ways to do this in Perl.  Strategies which require
       overriding UNIVERSAL::AUTOLOAD can use this interface instead to share
       that method with the superloader, and with class gnerators.

       When Perl is unable to find a subroutine/method, and all of the class
       loaders are exhausted, callbacks registered via sugar() are called.
       The callbacks recieve the class name, method name, and parameters of
       the call.

       If the callback returns nothing, Class::Autouse will continue to
       iterate through other callbacks.	 The first callback which returns a
       true value will end iteration.  That value is expected to be a CODE
       reference which will respond to the AUTOLOAD call.

       Note: The sugar callback(s) will only be fired by UNIVERSAL::AUTOLOAD
       after all other attempts at loading the class are done, and after
       attempts to use regular AUTOLOAD to handle the method call.  It is
       never fired by isa() or can().  It will fire repatedly for the same
       class.  To generate classes, use the regular CODE ref support in
       autouse().

       Syntactic Sugar Example

	   use Class::Autouse;
	   Class::Autouse->sugar(
	       sub {
		   my $caller = caller(1);
		   my ($class,$method,@params) = @_;
		   shift @params;
		   my @words = ($method,$class,@params);
		   my $sentence = join(" ",@words);
		   return sub { $sentence };
	       }
	   );

	   $x = trolls have big ugly hairy feet;

	   print $x,"\n";
	   # trolls have big ugly hairy feet

   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.

       Note that dynamically generated classes and classes loaded via regex
       CANNOT be pre-loaded automatically before forking child processes.
       They will still be loaded on demand, often in the child process.	 See
       prefork below.

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

       Since modules generated via callback or regex cannot be loaded
       automatically by prefork in a generic way, it's advised to use prefork
       directly to load/generate classes when using mod_perl.

   Performance Optimizatons
       :nostat
	   Described above, this option is useful when the module in question
	   is on remote disk.

       :noprebless
	   When set, Class::Autouse presumes that objects which are already
	   blessed have their class loaded.

	   This is true in most cases, but will break if the developer intends
	   to reconstitute serialized objects from Data::Dumper, FreezeThaw or
	   its cousins, and has configured Class::Autouse to load the involved
	   classes just-in-time.

       :staticisa
	   When set, presumes that @ISA will not change for a class once it is
	   loaded.  The greatest grandparent of a class will be given back the
	   original can/isa implementations which are faster than those
	   Class::Autouse installs into UNIVERSAL.  This is a performance
	   tweak useful in most cases, but is left off by default to prevent
	   obscure bugs.

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

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

AUTHORS
       Adam Kennedy <cpan@ali.as>

       Scott Smith <sakoht@cpan.org>

       Rob Napier <rnapier@employees.org>

SEE ALSO
       autoload, autoclass

COPYRIGHT
       Copyright 2002 - 2012 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.

perl v5.14.2			  2012-02-03		     Class::Autouse(3)
[top]

List of man pages available for Pidora

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net