NAME
Object::Pad::SlotAttr::Final
- declare Object::Pad
slots readonly after construction
SYNOPSIS
use
Object::Pad;
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 slot attribute for Object::Pad-based classes, which declares that the slot 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 slot 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.
SLOT ATTRIBUTES
:Final
has
$slot
:Final ...;
has
$slot
:Final ... = DEFAULT;
Declares that the slot 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 slot variable.
has
$slot
:Final;
ADJUST {
$slot
= 123; }
# this is permitted
method m {
$slot
= 456; }
# this will fail
Note that this is only a shallow readonly setting; if the slot 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>