Class::MethodMaker::V1Compat(3) User Contributed Perl Documentation Class::MethodMaker::V1Compat(3)

Class::MethodMaker::V1Compat - V1 compatibility code for C::MM

This class is for internal implementation only. It is not a public API.

Class::MethodMaker version 2 strives for backward-compatibility with version 1 as far as possible. That is to say, classes built with version 1 should work with few if any changes. However, the calling conventions for building new classes are significantly different: this is necessary to achieve a greater consistency of arguments.

Version 2 takes all arguments within a single arrayref:

use Class::MethodMaker
  [ scalar => 'a' ];

If arguments are presented as a list, then Class::MethodMaker assumes that this is a version 1 call, and acts accordingly. Version 1 arguments are passed and internally rephrased to version 2 arguments, and passed off to the version 2 engine. Thus, the majority of version 1 calls can be upgraded to version 2 merely by rephrasing. However, there are a number of behaviours that in version 1 that are internally inconsistent. These behaviours are mimicked in version 1 mode as far as possible, but are not reproducible in version 2 (to allow version 2 clients to rely on a more internally consistent interface).

The nearest equivalent to each 1 component (slot) available in version 2 is shown below using the indicated data-structures & options to create a component called "a" that mimics the V1 component behaviour as closely as possible:

use Class::MethodMaker
  [ abstract => 'a' ];
Boolean is available as a backwards compatibility hack, but there is currently no V2 equivalent. It is likely that some replacement mechanism will be introduced in the future, but that it will be incompatible with the version 1 boolean.
use Class::MethodMaker
  [ scalar => 'a' ];

Let's face it, the v1 store-if-it's-a-coderef-else-retrieve semantics are rather broken. How do you pass a coderef as argument to one of these? It is on the TODO list to recognize code as fundamental restricted type (analogous to INTEGER), which would add in a *_invoke method.

use Class::MethodMaker
  [ copy => 'a' ];

The v2 method is the same as v1.

use Class::MethodMaker
  [ scalar => [{-type => Class::MethodMaker::Constants::INTEGER}, 'a'] ];
use Class::MethodMaker
  [ copy => [ -deep => 'a' ] ];
use Class::MethodMaker
  [ scalar => [{ -store_cb => sub {
                                defined $_[1] ? ( defined $_[3] ?
                                                  "$_[3] $_[1]" : $_[1] )
                                              : undef;
                              }
               },
               'a' ]
  ];
use Class::MethodMaker
  [ scalar => 'a' ];
use Class::MethodMaker
  [ hash => 'a' ];
Although v1 calls will continue to work, this is not supported in v2.
Although v1 calls will continue to work, this is not supported in v2.
use Class::MethodMaker
  [ list => 'a' ];

Note that the "*" method now sets the whole array if given arguments.

See "code".
use Class::MethodMaker
  [ new => 'a' ];
use Class::MethodMaker
  [ new => [ -hash => 'a' ] ];
use Class::MethodMaker
  [ new => [ -hash => -init => 'a' ] ];
Although v1 calls will continue to work, this is not supported in v2, for it is a trivial application of "new_with_init".
use Class::MethodMaker
  [ new => [ -init => 'a' ] ];
use Class::MethodMaker
  [ scalar => [{ -type    => 'MyClass',
                 -forward => [qw/ method1 method2 /] }, 'a' ]
  ];
use Class::MethodMaker
  [ hash => [{ -type      => 'MyClass',
               -forward   => [qw/ method1 method2 /],
               -tie_class => 'Tie::MyTie',
               -tie_args  => [qw/ foo bar baz /],
             }, 'a' ]
  ];
use Class::MethodMaker
  [ array => [{ -type      => 'MyClass',
                -forward   => [qw/ method1 method2 /],
                -tie_class => 'Tie::MyTie',
                -tie_args  => [qw/ foo bar baz /],
              }, 'a' ]
  ];
use Class::MethodMaker
  [ scalar => [{ -store_cb => sub {
                                die "Already stored $_[3]"
                                  if @_ > 3;
                              }
               },
               'a' ]
  ];
use Class::MethodMaker
  [ scalar => [{ -store_cb => sub {
                                die "Already stored $_[3]"
                                  if @_ > 3;
                              },
                 -static   => 1,
               },
               'a' ]
  ];
use Class::MethodMaker
  [ new => [ -singleton => -hash => -init => 'a' ] ];
use Class::MethodMaker
  [ scalar => [ -static => 'a' ], ];
use Class::MethodMaker
  [ hash => [ -static => 'a' ], ];
use Class::MethodMaker
  [ list => [ -static => 'a' ], ];
use Class::MethodMaker
  [ hash => [ { -tie_class => 'MyTie',
                -tie_args  => [qw/ foo bar baz /],
              } => 'a' ], ];
use Class::MethodMaker
  [ array => [ { -tie_class => 'MyTie',
                 -tie_args  => [qw/ foo bar baz /],
               } => 'a' ], ];
use Class::MethodMaker
  [ scalar => [ { -tie_class => 'MyTie',
                  -tie_args  => [qw/ foo bar baz /],
                } => 'a' ], ];

The following version 1 component (slot) types are not currently supported in version 2:

Email the development mailing list "class-mmaker-devel@lists.sourceforge.net".

Martyn J. Pearce

Copyright (c) 2003, 2004 Martyn J. Pearce. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

2022-05-29 perl v5.36.0