Damien Krotkine home

MooX::LvalueAttribute - Lvalue accessors in Moo

Yesterday I was reading Joel’s post, where he lists great Perl things he’s seen done lately. Indeed these are great stuff. I was particulary interested by his try at playing with Lvalue accessors.

I thought that it would be a great exercise to try to implement it in Moo, as an additional feature, trying to get rid of the AUTOLOAD. Also, I was willing to avoid doing a tie every time an instance attribute accessor was called. Surely, I needed to tie only once per instance and per attribute, not each time the attribute is accessed.

So I started hacking on the code of Moo. Getting rid of the AUTOLOAD was easy, as I could change the way the accessor generator was, well, generating the, err, accessors.

Shortly after I started having issues to cache a tied variable. I asked the all-mighty Vincent Pit, and he found a solution for my tied variables, but more importanlty pointed me to Variable::Magic, which is faster, more flexible and powerful.

All I needed was to move my hacks in a proper Role, and wrap the whole in a module, and push it on CPAN. Tadaa, MooX::LvalueAttribute was born.

In the process I used play-perl to register my quests, and exchanged thoughts with Joel Berger. I think I’m going to use this website more, see if it can boost my productivity, and help me figure out what’s really important to do.

On IRC, haarg discovered a bug and recommended to use so-called fieldhashes, from Hash::Util::FieldHash::Compat. At the end of the day, I only acted as a glue between different pieces of knowledges, and that was very satisfactory.


MooX::LvalueAttribute is a module that provides Lvalue attributes:

package App;
use Moo;
use MooX::LvalueAttribute;

has name => (
  is => 'rw',
  lvalue => 1,

# Elsewhere
my $app = App->new(name => 'foo');

$app->name = 'Bar';

print $app->name;  # Bar


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