Track dirtied attributes
Perl Perl 6
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MooseX::TrackDirty::Attributes - Track dirtied attributes


This document describes version 2.004 of MooseX::TrackDirty::Attributes - released October 12, 2016 as part of MooseX-TrackDirty-Attributes.


package Foo;
use Moose;
use MooseX::TrackDirty::Attributes;

# tracking accessor is not automagically applied
has foo => (is => 'rw');

# one_is_dirty() is generated by default
has one => (traits => [ TrackDirty ], is => 'rw');

# dirtyness "accessor" is generated as two_isnt_clean()
has two      => (
    traits   => [ TrackDirty ],
    is       => 'rw',
    is_dirty => 'two_isnt_clean',

# three_is_dirty() and original_value_of_three() are generated
has three => (
    traits         => [ TrackDirty ],
    is             => 'rw',
    original_value => 'original_value_of_three',

# ...meanwhile, at the bat-cave

package main;
my $foo = Foo->new();

$foo->one_is_dirty; # false


MooseX::TrackDirty::Attributes does the necessary metaclass fiddling to track if attributes are dirty; that is, if they're set to some value and then set again, to another value. (The setting can be done by the constructor, builder, default, accessor, etc.)

An attribute can be returned to a clean state by invoking its clearer.


Note that with one (significant) exceptions we can only track dirtiness at the very first level. That is, if you have an attribute that is a HashRef, we can tell that the _attribute_ is dirty if and only if the actual ref changes, but not if the HashRef's keys/values change. e.g.

$self->hashref({ new => 'hash' })

would render the 'hashref' attribute dirty, but

$self->hashref->{foo} = 'bar'

would not.

In plainer language: we can only tell if an attribute's value is dirty if our accessors are used to modify its values.

The exception to this is...


We now track when a native trait accessor is used to change the contents of the attribute; this is considered to make the attribute value dirty.

This is still new and experimental, so feedback is quite welcome :)


To track a given attribute, the trait must be applied. This package exports a "TrackDirty" function that returns the full (ridiculously long) package name of the trait.

Once applied, we have two additional options that can be passed to the attribute constructor (usually via 'has'):

  • is_dirty => method_name

    is_dirty controls what the name of the "is this attribute's value dirty?" accessor is (returning true on dirty; false otherwise):

    By default, the accessor is installed as "{attribute_name}_is_dirty". If a legal method name is passed, the accessor is installed under that name. Otherwise we blow up.

  • original_value => method_name

    original_value controls what the name for the original value accessor is installed (returns the original value if dirty, undef otherwise):

    By default, we do not install an original_value accessor. If a legal method name is passed, the accessor is installed under that name. Otherwise we blow up.

  • cleaner => method_name

    cleaner controls what the name for the cleaner accessor is installed (marks a dirty attribute as clean without clearing):

    By default, we do not install an cleaner accessor. If a legal method name is passed, the accessor is installed under that name. Otherwise we blow up.


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


Chris Weyl

I'm a material boy in a material world

Please note I do not expect to be gittip'ed or flattr'ed for this work, rather it is simply a very pleasant surprise. I largely create and release works like this because I need them or I find it enjoyable; however, don't let that stop you if you feel like it ;)

Flattr, Gratipay, or indulge my Amazon Wishlist... If and *only* if you so desire.


Gianni Ceccarelli


This software is Copyright (c) 2011 by Chris Weyl.

This is free software, licensed under:

The GNU Lesser General Public License, Version 2.1, February 1999