aliased(3pm)
NAME
aliased - Use shorter versions of class names.
VERSION
version 0.34
SYNOPSIS
# Class name interface
use aliased 'My::Company::Namespace::Customer';
my $cust = Customer->new;
use aliased 'My::Company::Namespace::Preferred::Customer' => 'Preferred';
my $pref = Preferred->new;
# Variable interface
use aliased;
my $Customer = alias "My::Other::Namespace::Customer";
my $cust = $Customer->new;
my $Preferred = alias "My::Other::Namespace::Preferred::Customer";
my $pref = $Preferred->new;
DESCRIPTION
"aliased" is simple in concept but is a rather handy module. It loads
the class you specify and exports into your namespace a subroutine that
returns the class name. You can explicitly alias the class to another
name or, if you prefer, you can do so implicitly. In the latter case,
the name of the subroutine is the last part of the class name. Thus,
it does something similar to the following:
#use aliased 'Some::Annoyingly::Long::Module::Name::Customer';
use Some::Annoyingly::Long::Module::Name::Customer;
sub Customer {
return 'Some::Annoyingly::Long::Module::Name::Customer';
}
my $cust = Customer->new;
This module is useful if you prefer a shorter name for a class. It's
also handy if a class has been renamed.
(Some may object to the term "aliasing" because we're not aliasing one
namespace to another, but it's a handy term. Just keep in mind that
this is done with a subroutine and not with typeglobs and weird
namespace munging.)
Note that this is only for "use"ing OO modules. You cannot use this to
load procedural modules. See the "Why OO Only?" section. Also, don't
let the version number fool you. This code is ridiculously simple and
is just fine for most use.
Implicit Aliasing
The most common use of this module is:
use aliased 'Some::Module::name';
"aliased" will allow you to reference the class by the last part of
the class name. Thus, "Really::Long::Name" becomes "Name". It does
this by exporting a subroutine into your namespace with the same name
as the aliased name. This subroutine returns the original class name.
For example:
use aliased "Acme::Company::Customer";
my $cust = Customer->find($id);
Note that any class method can be called on the shorter version of the
class name, not just the constructor.
Explicit Aliasing
Sometimes two class names can cause a conflict (they both end with
"Customer" for example), or you already have a subroutine with the same
name as the aliased name. In that case, you can make an explicit alias
by stating the name you wish to alias to:
use aliased 'Original::Module::Name' => 'NewName';
Here's how we use "aliased" to avoid conflicts:
use aliased "Really::Long::Name";
use aliased "Another::Really::Long::Name" => "Aname";
my $name = Name->new;
my $aname = Aname->new;
You can even alias to a different package:
use aliased "Another::Really::Long::Name" => "Another::Name";
my $aname = Another::Name->new;
Messing around with different namespaces is a really bad idea and you
probably don't want to do this. However, it might prove handy if the
module you are using has been renamed. If the interface has not
changed, this allows you to use the new module by only changing one
line of code.
use aliased "New::Module::Name" => "Old::Module::Name";
my $thing = Old::Module::Name->new;
Import Lists
Sometimes, even with an OO module, you need to specify extra arguments
when using the module. When this happens, simply use "Explicit
Aliasing" followed by the import list:
Snippet 1:
use Some::Module::Name qw/foo bar/;
my $o = Some::Module::Name->some_class_method;
Snippet 2 (equivalent to snippet 1):
use aliased 'Some::Module::Name' => 'Name', qw/foo bar/;
my $o = Name->some_class_method;
Note: remember, you cannot use import lists with "Implicit Aliasing".
As a result, you may simply prefer to only use "Explicit Aliasing" as a
matter of style.
alias()
This function is only exported if you specify "use aliased" with no
import list.
use aliased;
my $alias = alias($class);
my $alias = alias($class, @imports);
"alias()" is an alternative to "use aliased ..." which uses less magic
and avoids some of the ambiguities.
Like "use aliased" it "use"s the $class (pass in @imports, if given)
but instead of providing an "Alias" constant it simply returns a scalar
set to the $class name.
my $thing = alias("Some::Thing::With::A::Long::Name");
# Just like Some::Thing::With::A::Long::Name->method
$thing->method;
The use of a scalar instead of a constant avoids any possible ambiguity
when aliasing two similar names:
# No ambiguity despite the fact that they both end with "Name"
my $thing = alias("Some::Thing::With::A::Long::Name");
my $other = alias("Some::Other::Thing::With::A::Long::Name");
and there is no magic constant exported into your namespace.
The only caveat is loading of the $class happens at run time. If
$class exports anything you might want to ensure it is loaded at
compile time with:
my $thing;
BEGIN { $thing = alias("Some::Thing"); }
However, since OO classes rarely export this should not be necessary.
prefix() (experimental)
This function is only exported if you specify "use aliased" with no
import list.
use aliased;
Sometimes you find you have a ton of packages in the same top-level
namespace and you want to alias them, but only use them on demand. For
example:
# instead of:
MailVerwaltung::Client::Exception::REST::Response->throw()
my $error = prefix('MailVerwaltung::Client::Exception');
$error->('REST::Response')->throw(); # same as above
$error->()->throw; # same as MailVerwaltung::Client::Exception->throw
Why OO Only?
Some people have asked why this code only support object-oriented
modules (OO). If I were to support normal subroutines, I would have to
allow the following syntax:
use aliased 'Some::Really::Long::Module::Name';
my $data = Name::data();
That causes a serious problem. The only (reasonable) way it can be
done is to handle the aliasing via typeglobs. Thus, instead of a
subroutine that provides the class name, we alias one package to
another (as the namespace module does.) However, we really don't want
to simply alias one package to another and wipe out namespaces willy-
nilly. By merely exporting a single subroutine to a namespace, we
minimize the issue.
Fortunately, this doesn't seem to be that much of a problem. Non-OO
modules generally support exporting of the functions you need and this
eliminates the need for a module such as this.
EXPORT
This modules exports a subroutine with the same name as the "aliased" name.
SEE ALSO
The namespace module.
THANKS
Many thanks to Rentrak, Inc. (http://www.rentrak.com/) for graciously allowing me to replicate the functionality of some of their internal code.
AUTHOR
Curtis "Ovid" Poe <ovid@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2005 by Curtis "Ovid" Poe. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
CONTRIBUTORS
* Karen Etheridge <ether@cpan.org> * Curtis Poe <ovid@cpan.org> * Ovid <curtis_ovid_poe@yahoo.com> * Florian Ragwitz <rafl@debian.org> * Grzegorz RoXniecki <xaerxess@gmail.com> * Father Chrysostomos <sprout@cpan.org> * Belden Lyman <belden@shutterstock.com> * Olivier Mengue <dolmen@cpan.org>
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