man Class::MethodMaker::V1Compat (3): V1 compatibility code for C::MM

SYNOPSIS

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

DESCRIPTION

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).

Version 2 Implementations

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:

abstract

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

boolean

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.

code

  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.

copy

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

The v2 method is the same as v1.

counter

  use Class::MethodMaker
    [ scalar => [{-type => Class::MethodMaker::Constants::INTEGER}, 'a'] ];

copy

deep_copy

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

get_concat

  use Class::MethodMaker
    [ scalar => [{ -store_cb => sub {
                                  defined $_[1] ? ( defined $_[3] ?
                                                    "$_[3] $_[1]" : $_[1] )
                                                : undef;
                                }
                 },
                 'a' ]
    ];

get_set

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

hash

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

key_attrib

Although v1 calls will continue to work, this is not supported in v2.

key_with_create

Although v1 calls will continue to work, this is not supported in v2.

list

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

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

method

See "code".

new

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

new_hash_init

  use Class::MethodMaker
    [ new => [ -hash => 'a' ] ];

new_hash_with_init

  use Class::MethodMaker
    [ new => [ -hash => -init => 'a' ] ];

new_with_args

Although v1 calls will continue to work, this is not supported in v2, for it is a trivial application of "new_with_init".

new_with_init

  use Class::MethodMaker
    [ new => [ -init => 'a' ] ];

object

  use Class::MethodMaker
    [ scalar => [{ -type    => 'MyClass',
                   -forward => [qw/ method1 method2 /] }, 'a' ]
    ];

object_tie_hash

  use Class::MethodMaker
    [ hash => [{ -type      => 'MyClass',
                 -forward   => [qw/ method1 method2 /],
                 -tie_class => 'Tie::MyTie',
                 -tie_args  => [qw/ foo bar baz /],
               }, 'a' ]
    ];

object_tie_list

  use Class::MethodMaker
    [ array => [{ -type      => 'MyClass',
                  -forward   => [qw/ method1 method2 /],
                  -tie_class => 'Tie::MyTie',
                  -tie_args  => [qw/ foo bar baz /],
                }, 'a' ]
    ];

set_once

  use Class::MethodMaker
    [ scalar => [{ -store_cb => sub {
                                  die "Already stored $_[3]"
                                    if @_ > 3;
                                }
                 },
                 'a' ]
    ];

set_once_static

  use Class::MethodMaker
    [ scalar => [{ -store_cb => sub {
                                  die "Already stored $_[3]"
                                    if @_ > 3;
                                },
                   -static   => 1,
                 },
                 'a' ]
    ];

singleton

  use Class::MethodMaker
    [ new => [ -singleton => -hash => -init => 'a' ] ];

static_get_set

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

static_hash

  use Class::MethodMaker
    [ hash => [ -static => 'a' ], ];

static_list

  use Class::MethodMaker
    [ list => [ -static => 'a' ], ];

tie_hash

  use Class::MethodMaker
    [ hash => [ { -tie_class => 'MyTie',
                  -tie_args  => [qw/ foo bar baz /],
                } => 'a' ], ];

tie_list

  use Class::MethodMaker
    [ array => [ { -tie_class => 'MyTie',
                   -tie_args  => [qw/ foo bar baz /],
                 } => 'a' ], ];

tie_scalar

  use Class::MethodMaker
    [ scalar => [ { -tie_class => 'MyTie',
                    -tie_args  => [qw/ foo bar baz /],
                  } => 'a' ], ];

Caveats & Expected Breakages

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

grouped_fields
hash_of_lists
listed_attrib
struct

EXAMPLES

BUGS

REPORTING BUGS

Email the development mailing list "[email protected]".

AUTHOR

Martyn J. Pearce