NAME

Object::Pad::Operator::Of - access fields of other instances

SYNOPSIS

On Perl v5.38 or later:

use v5.38;
use Object::Pad;
use Object::Pad::Operator::Of;

class Bucket {
   field $size :param;

   use overload '<=>' => method ($other, $) {
      return $size <=> $size of $other;
   };
}

DESCRIPTION

This module provides an infix operator for accessing fields of other instances of an Object::Pad class, even if those fields do not have accessor methods. This allows code to be written that can look into the inner workings of other instances of the same class (or subclasses thereof), in order to implement particular behaviours, such as sorting comparisons.

Support for custom infix operators was added in the Perl 5.37.x development cycle and is available from development release v5.37.7 onwards, and therefore in Perl v5.38 onwards. The documentation of XS::Parse::Infix describes the situation in more detail.

OPERATORS

of

my $value = $field of $other;

Yields the current value of the given field of a different instance than $self. The field variable, on the left of the operator, must be lexically visible in the current scope. The expression on the right must yield an instance of the class that defines the field (or some subclass of it); if not an exception is thrown.

TODO

• Try to find a better operator name, which puts the object instance on the left and the field on the right.

• Look into whether regular subs can also use of expressions. Currently no fields are visible due to the way that Object::Pad implements methods.

• Look into whether it might be possible to use of expressions as lvalues, for mutation or assignment.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>