NAME

       "Object::Pad::FieldAttr::Final" - declare "Object::Pad" fields readonly after construction

SYNOPSIS

          use Object::Pad;
          use Object::Pad::FieldAttr::Final;

          class Rectangle {
             has $width  :param :reader :Final;
             has $height :param :reader :Final;

             has $area :reader :Final;

             ADJUST {
                $area = $width * $height;
             }
          }

DESCRIPTION

       This module provides a third-party field attribute for Object::Pad-based classes, which
       declares that the field it is attached to shall be set as readonly when the constructor
       returns, disallowing further modification to it.

       WARNING The ability for Object::Pad to take third-party field attributes is still new and
       highly experimental, and subject to much API change in future. As a result, this module
       should be considered equally experimental.

FIELD ATTRIBUTES

   :Final
          has $field :Final ...;
          has $field :Final ... = DEFAULT;

       Declares that the field variable will be set readonly at the end of the constructor, after
       any assignments from ":param" declarations or "ADJUST" blocks. At this point, the value
       cannot otherwise be modified by directly writing into the field variable.

          has $field :Final;

          ADJUST { $field = 123; }    # this is permitted

          method m { $field = 456; }  # this will fail

       Note that this is only a shallow readonly setting; if the field variable contains a
       reference to a data structure, that structure itself remains mutable.

          has $aref :Final;
          ADJUST { $aref = []; }

          method more { push @$aref, "another"; }   # this is permitted

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>