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.

    There is no ability to declare 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.

    The following class attributes are supported:

  :isa

       :isa(CLASS)
    
       :isa(CLASS CLASSVER)

    Since version 0.02.

    Declares a superclass that this class extends. At most one superclass
    is supported.

    If the package providing the superclass does not exist, an attempt is
    made to load it by code equivalent to

       require CLASS ();

    and thus it must either already exist, or be locatable via the usual
    @INC mechanisms.

    An optional version check can also be supplied; it performs the
    equivalent of

       BaseClass->VERSION( $ver )

 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.

    Attributes are not supported; in particular the :params attribute of
    Object::Pad v0.70.

 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>

