Class Attributes with Moo ?

mascip has asked for the wisdom of the Perl Monks concerning the following question:

Hello,
with Moose i used MooseX::ClassAttribute to declare class attributes. I am thinking about transitioning to Moo, and am wondering how to best deal with class attributes.

For example, i am sharing a timer between all the objects of a class. I used to write

package MyClass;
use Moose;
use MooseX::ClassAttribute;

class_has 'timer' => (
    is       => 'ro',
    isa      => 'Benchmark::Timer',
    default  => sub { Benchmark::Timer->new() },
);
[download]

Now with Moo i have just used the "good old way" (maybe not that "good"?) :

package MyClass;
use Moo;

my $timer = Benchmark::Timer->new();
[download]

Is there any nicer way to do that?

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Re: Class Attributes with Moo ? by tobyink (Canon) on Dec 27, 2012 at 07:53 UTC
Yes, this is a MooX module I've been meaning to write for some time. Like you, I've been using package variables, but a proper class attribute would give you delegation, type constraints, triggers, etc. I may have a stab at writing something along these lines in the next couple of weeks. I just need to delve into the Method::Generate::* code to see how feasible it might be. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply]
Re^2: Class Attributes with Moo ? by mascip (Pilgrim) on Dec 27, 2012 at 16:22 UTC
Thank you for your reply :-) I was wondering if i was missing anything. In the future if i need to use inheritance, i might put this timer as a simple attribute, and pass it to my objects from the client code. It's giving some non-related job to the client, but it should do the trick. I'll keep an eye open, in case you created a new MooX module. Sorry i cannot help : i don't have the skills nor the time to develop them right now.	[reply]
Re^3: Class Attributes with Moo ? by tobyink (Canon) on Jan 01, 2013 at 10:37 UTC
OK, MooX::ClassAttribute is now on CPAN. Subclassing Method::Generate::Accessor to generate class attributes was relatively easy. The hard parts were getting class attributes defined in roles to work, and getting Moose inflation going. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply]
Re^4: Class Attributes with Moo ? by mascip (Pilgrim) on Jan 01, 2013 at 16:37 UTC
Re^2: Class Attributes with Moo ? by mascip (Pilgrim) on Dec 28, 2012 at 07:29 UTC
I don't have the time to try it today, but maybe tomorrow : Class::Data::Inheritable might do the trick according to its documentation. This could be enough for me right now. The annoying bit is that you have to inherit from Class::Data::Inheritable. I'm not sure how annoying that could be though.	[reply]