Class::Loader(3pm)

💖 Class::Loader 💖

okay bestie, welcome to Class::Loader — a Perl module in the User Contributed Perl Documentation corner of the manual, and honestly? it's giving runtime-decision-maker realness. it's an inheritable class that loads modules on demand and builds you objects. obsessed. 🫶

✨ NAME ✨

Class::Loader — loads modules and creates objects on demand, no cap. 🌈

🌸 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 => [ ],
                     }
            );

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🦋 DESCRIPTION 🦋

so like, some apps out here are not about deciding at compile time which module they're gonna use. they wanna wait till runtime, you know? main character energy: postponing the decision. 💅 and that's totally possible in perl, and it's a genuinely useful trick when you don't know the type of data at compile time and your app doesn't wanna be out here pre-compiling every module that could theoretically handle every type of data it might ever work with. loading modules at runtime also lowkey unlocks flexible interfaces for perl modules — the module can let the programmer pick which modules it uses instead of hard-coding their names. periodt.

Class::Loader is an inheritable class that gives you a method, _load(), which loads a module from disk and constructs an object by calling its constructor. it ALSO gives you a way to map module names + their associated metadata to symbolic names, and then you can use those symbolic names instead of module names inside _load(). iconic behaviour tbh. ✨

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👑 METHODS 👑

new()

a basic constructor, bestie. use it to make an object of Class::Loader in case you don't wanna inherit Class::Loader. that's it, that's the vibe. 🎀

_load()

_load() loads a module and calls its constructor. it returns the newly constructed object on success, or a non-true value on failure (yes, literally non-true, so check your return values 🌸). the first argument can be the name of the key in which the returned object gets stored — and that argument is optional. the second (or the first) argument is a hash which can take the following keys:

• Module — the name of the class to load. ⚠️ heads up: it is not the module's filename, bestie, don't get it twisted. it's the class name.
• Name — the symbolic name of the module, as defined with _storemap(). either Module or Name must be present in a call to _load(). one of them, minimum, no skipping. 💜
• Constructor — the 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 just call the constructor without any arguments at all. 😌
• 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 you've got a pre-configured CPAN shell available, so like, set that up first or it's not gonna happen. 🫶

_storemap()

Class::Loader keeps a class table that maps symbolic names to the parameters accepted by _load(). it takes a hash as its argument, where the keys are symbolic names and the values are hash references containing a set of _load() arguments. here's the glow-up in code form:

$self->_storemap ( "URL" => { Module => "Filter::URL",
                              Constructor => "foo",
                              Args => [qw(bar baz)],
                            }
                 );

# time passes...

$self->{handler} = $self->_load ( Name => 'URL' );

see? you store it once, you use it later. the way that works is so satisfying. 🍓

_retrmap()

_retrmap() returns the entire map stored with Class::Loader. Class::Loader keeps separate maps for different classes, and _retrmap() returns the map that's valid in the caller class — aka your class's map, not somebody else's. 🧚

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💜 SEE ALSO 💜

AnyLoader(3) — go look, bestie, iykyk. 📚

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🌟 AUTHOR 🌟

Vipul Ved Prakash, <mail@vipul.net> — thank you for your service, legend. 👑

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📜 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. 💖 (so like, go forth, but respect the terms, fr fr.)

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and that's the whole page, bestie!! this one's from perl v5.36.0, dated 2022-10-13, and it's the Class::Loader(3pm) manual — mwah, go load some modules at runtime. 💅✨🦋