Object::Pad::MetaFunctions(3pm)

NAME
"Object::Pad::MetaFunctions" - utility functions for "Object::Pad" classes

SYNOPSIS
   use v5.36;
   use Object::Pad::MetaFunctions qw( deconstruct_object );

   sub debug_print_object ( $obj )
   {
      my ( $classname, @repr ) = deconstruct_object( $obj );

      say "An object of type $classname having:";

      foreach my ( $fieldname, $value ) ( @repr ) {
         printf "%30s = %s\n", $fieldname, $value;
      }
   }

DESCRIPTION
This module contains a number of miscellaneous utility functions for working with Object::Pad-based classes or instances thereof.

These functions all involve a certain amount of encapsulation-breaking into the object instances being operated on. This sort of thing shouldn't be encouraged in most regular code, but there can be occasions when it is useful; such as debug printing of values, generic serialisation, or tightly-coupled unit tests that wish to operate on the internals of the object instances they test.

Therefore, use of these functions should be considered "last-resort". Consider carefully the sorts of things you are trying to do with them, and whether this kind of reaching into the internals of an object, bypassing all of its interface encapsulation, is really the best technique to achieve your goal.

FUNCTIONS

  metaclass
   $metaclass = metaclass( $obj );

Since version 0.67.

Returns the Object::Pad::MOP::Class metaclass associated with the class that the object is an instance of.

  deconstruct_object
   ( $classname, @repr ) = deconstruct_object( $obj );

Since version 0.67.

Returns a list of perl values containing a representation of all the fields in the object instance. This representation form may be useful for tasks such as debug printing or serialisation of the instance. This list is prefixed by the name of the class of instance as a plain string.

The exact form of this representation is still experimental and may change in a later version. Currently, it takes the form of an even-sized list of key/value pairs, associating field names with their values. Each key gives the name of a component class and the full name of the field within it, separated by a dot (".").

   'CLASSNAME.$FIELD1' => VALUE, 'CLASSNAME.@FIELD2' => VALUE, ...

In the case of scalar fields, the value is the actual value of that field. In the case of array or hash fields, the value in the repr list is a reference to an anonymous copy of the value stored in the field.

   'CLASSNAME.$SCALARFIELD' => $VALUE,
   'CLASSNAME.@ARRAYFIELD'  => [ @VALUE ],
   'CLASSNAME.%HASHFIELD'   => { %VALUE },

The pairs are ordered, with the actual object class type first, followed by any roles added by that class, then each parent class recursively. Within each component class, the fields are given in declared order.

This reliable ordering may be useful when printing values in human-readable form, or serialising to some stable storage.

  ref_field
   $fieldref = ref_field( $fieldname, $obj );

Since version 0.67.

Returns a reference to the named field storage variable of the given instance object. The $fieldname should be specified as the class name and the field name separated by a dot (".") (as per "deconstruct_object").

The class name may also be omitted; at which point the first occurrence of a field of the given name found in any component class it matched instead.

If no matching field is found, an exception is thrown.

Be careful when using this function as it has the ability to expose instance fields in a way that allows them to be modified. For a safer alternative when only read access is required, use "get_field" instead.

  get_field
   $scalar = get_field( $fieldname, $obj );
   @array  = get_field( $fieldname, $obj );
   %hash   = get_field( $fieldname, $obj );

Since version 0.67.

Returns the value of the named field of the given instance object. Behaves correctly given context; namely, that when invoked on array or hash fields in scalar context it will return the number of elements or keys, or in list context will return the list of elements or key/value pairs.

AUTHOR
Paul Evans <leonerd@leonerd.org.uk>