Class::MakeMethods::Emulator::Singleton - Emulate Class::Singleton


Class-MakeMethods documentation Contained in the Class-MakeMethods distribution.

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NAME

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Class::MakeMethods::Emulator::Singleton - Emulate Class::Singleton

SYNOPSIS

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  use Class::MakeMethods::Emulator::Singleton; 

  # returns a new instance
  my $one = Class::MakeMethods::Emulator::Singleton->instance();

  # returns same instance
  my $two = Class::MakeMethods::Emulator::Singleton->instance();   




COMPATIBILITY

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This module emulates the functionality of Class::Singleton, using Class::MakeMethods to generate similar methods.

You may use it directly, as shown in the SYNOPSIS above,

Furthermore, you may call use Class::MakeMethods::Emulator::Singleton '-take_namespace'; to alias the Class::Singleton namespace to this package, and subsequent calls to the original package will be transparently handled by this emulator. To remove the emulation aliasing, call use Class::MakeMethods::Emulator::Singleton '-release_namespace'.

Caution: This affects all subsequent uses of Class::Singleton in your program, including those in other modules, and might cause unexpected effects.

DESCRIPTION

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A Singleton describes an object class that can have only one instance in any system. An example of a Singleton might be a print spooler or system registry. This module implements a Singleton class from which other classes can be derived. By itself, the Class::Singleton module does very little other than manage the instantiation of a single object. In deriving a class from Class::Singleton, your module will inherit the Singleton instantiation method and can implement whatever specific functionality is required.

SEE ALSO

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See Class::MakeMethods for general information about this distribution.

See Class::MakeMethods::Emulator for more about this family of subclasses.

See Class::Singleton for documentation of the original module.

For a description and discussion of the Singleton class, see "Design Patterns", Gamma et al, Addison-Wesley, 1995, ISBN 0-201-63361-2.

See new in Class::MakeMethods::Hash and instance in Class::MakeMethods::ClassVar for documentation of the created methods.


Class-MakeMethods documentation Contained in the Class-MakeMethods distribution.

package Class::MakeMethods::Emulator::Singleton;

use strict;
require Class::MakeMethods::Emulator;

my $emulation_target = 'Class::Singleton';

sub import {
  my $mm_class = shift;
  if ( scalar @_ and $_[0] =~ /^-take_namespace/ and shift) {
    Class::MakeMethods::Emulator::namespace_capture(__PACKAGE__, $emulation_target);
  } elsif ( scalar @_ and $_[0] =~ /^-release_namespace/ and shift) {
    Class::MakeMethods::Emulator::namespace_release(__PACKAGE__, $emulation_target);
  }
  # The fallback should really be to NEXT::import.
  $mm_class->SUPER::import( @_ );
}

########################################################################

use Class::MakeMethods (
  'Template::Hash:new --with_values' => '_new_instance',
  'Template::ClassVar:instance --get_init' => [ 'instance', 
			{new_method=>'_new_instance', variable=>'_instance'} ]
);

########################################################################

1;

__END__