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Aspect::Library::Singleton(3pm) User Contributed Perl Documentation Aspect::Library::Singleton(3pm)


Aspect::Library::Singleton - A singleton aspect


  use Aspect;
  use Aspect::Singleton;
  aspect Singleton => 'Foo::new';
  my $f1 = Foo->new;
  my $f2 = Foo->new;
  # Both $f1 and $f2 refer to the same object


A reusable aspect that forces singleton behavior on a constructor. The constructor is defined by a pointcut spec: a string. regexp, or code ref.

It is slightly different from "Class::Singleton" (<>):

  • No specific name requirement on the constructor for the external interface, or for the implementation ("Class::Singleton" requires clients use "instance()", and that subclasses override "_new_instance()"). With aspects, you can change the cardinality of your objects without changing the clients, or the objects themselves.
  • No need to inherit from anything- use pointcuts to specify the constructors you want to memoize. Instead of pulling singleton behavior from a base class, you are pushing it in, using the aspect.
  • No package variable or method is added to the callers namespace

Note that this is just a special case of memoizing.


Adam Kennedy <>

Marcel Grünauer <>

Ran Eilam <>


Copyright 2001 by Marcel Grünauer

Some parts copyright 2009 - 2013 Adam Kennedy.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

2022-06-08 perl v5.34.0