NAME

Object::Pad::ClassAttr::Struct - declare an Object::Pad class to be struct-like

SYNOPSIS

   use Object::Pad;
   use Object::Pad::ClassAttr::Struct;

   class Colour :Struct {
      # These get :param :mutator automatically
      field $red   = 0;
      field $green = 0;
      field $blue  = 0;

      # Additional methods are still permitted
      method lightness {
         return ($red + $green + $blue) / 3;
      }
   }

   my $cyan = Colour->new( green => 1, blue => 1 );

   # A positional constructor is created automatically
   my $white = Colour->new_values(1, 1, 1);

DESCRIPTION

This module provides a third-party class attribute for Object::Pad-based classes, which applies some attributes automatically to every field added to the class, as a convenient shortcut for making structure-like classes.

CLASS ATTRIBUTES

:Struct

   class Name :Struct ... { ... }

Automatically applies the :param and :mutator attributes to every field defined on the class, meaning the constructor will accept parameters for each field to initialise the value, and each field will have an lvalue mutator method.

In addition, the class itself gains the :strict(params) attribute, meaning the constructor will check parameter names and throw an exception for unrecognised names.

Since version 0.04 a positional constructor class method called new_values is also provided into the class, which takes a value for every field positionally, in declared order.

   $obj = ClassName->new_values($v1, $v2, $v3, ...);

This positional constructor must receive as many positional arguments as there are fields in total in the class; even the optional ones. All arguments are required here.

Since version 0.05 the following options are permitted inside the attribute value parentheses:

:Struct(readonly)

Instances of this class do not permit fields to be modified after construction. The accessor is created using the :reader field attribute rather than :mutator.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>