Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
aliased(3)	      User Contributed Perl Documentation	    aliased(3)

       aliased - Use shorter versions of class names.

       version 0.34

	 # 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;

       "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.

       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

       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

	   # instead of:

	   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.

       This modules exports a subroutine with the same name as the "aliased"

       The namespace module.

       Many thanks to Rentrak, Inc. ( for graciously
       allowing	me to replicate	the functionality of some of their internal

       Curtis "Ovid" Poe <>

       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.

       o   Karen Etheridge <>

       o   Curtis Poe <>

       o   Ovid	<>

       o   Florian Ragwitz <>

       o   Grzegorz RoXniecki <>

       o   Father Chrysostomos <>

       o   Belden Lyman	<>

       o   Olivier Mengue <>

perl v5.32.0			  2015-01-03			    aliased(3)


Want to link to this manual page? Use this URL:

home | help