/ 
Feature-Compat-Class-0.01
River stage two • 12 direct dependents • 12 total dependents
/ Feature::Compat::Class

NAME

Feature::Compat::Class - make class syntax available

SYNOPSIS

use Feature::Compat::Class;

class Point {
   field $x;
   field $y;

   ADJUST {
      $x = $y = 0;
   }

   method move_to ($new_x, $new_y) {
      $x = $new_x;
      $y = $new_y;
   }

   method describe {
      say "A point at ($x, $y)";
   }
}

DESCRIPTION

This module provides the new class keyword and related others (method, field and ADJUST) in a forward-compatible way.

There is a branch of Perl development source code which provides this syntax, under the class named feature. If all goes well, this will become available in a stable release in due course. On such perls that contain the feature, this module simple enables it.

On older versions of perl before such syntax is availble in core, it is currently provided instead using the Object::Pad module, imported with a special set of options to configure it to only recognise the same syntax as the core perl feature, thus ensuring any code using it will still continue to function on that newer perl.

Perl Branch with feature 'class'

At time of writing, the use feature 'class' syntax is not part of mainline perl source but is available in a branch. That branch currently resides at https://github.com/leonerd/perl5/tree/feature-class/. It is intended this will be migrated to the main perl repository ahead of actually being merged once development has progressed further.

This module is a work-in-progress, because the underlying feature-class branch is too. Many of the limitations and inabilities listed below are a result of the early-access nature of this branch, and are expected to be lifted as work progresses towards a more featureful and complete implementation.

KEYWORDS

The keywords provided by this module offer a subset of the abilities of those provided by Object::Pad, restricted to specifically only what is commonly supported by the core syntax as well. In general, the reader should first consult the documentation for the corresponding Object::Pad keyword, but the following notes may be of interest:

class

class NAME { ... }
class NAME VERSION { ... }

class NAME; ...
class NAME VERSION; ...

See also "class" in Object::Pad.

Attributes are not supported. In particular, there is no ability to declare a superclass with :isa nor any roles with :does. The legacy subkeywords for these are equally not supported.

The :repr attribute is also not supported; the default representation type will always be selected.

The :strict(params) attribute is not available, but all constructed classes will behave as if the attribute had been declared. Every generated constructor will check its parameters for key names left unhandled by ADJUST blocks, and throw an exception if any remain.

method

method NAME { ... }
method NAME;

See also "method" in Object::Pad.

Attributes are not supported, other than the usual ones provided by perl itself. Of these, only :lvalue is particularly useful.

Lexical methods are not supported.

field

field $NAME;
field @NAME;
field %NAME;

See also "field" in Object::Pad.

Attributes are not supported. In particular, rather than using the accessor-generator attributes you will have to create accessor methods yourself; such as

field $var;
method var { return $var; }
method set_var ($new_var) { $var = $new_var; }

Field initialiser blocks are also not supported. Instead, you will have to use an ADJUST block to initialise a field:

field $five;
ADJUST { $five = 5; }

ADJUST

ADJUST { ... }

See also "ADJUST" in Object::Pad.

Other Keywords

The following other keywords provided by Object::Pad are not supported here at all:

role

BUILD, ADJUSTPARAMS

has

requires

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>