madsen / moosex-attributetree

Perl module to let Moose objects inherit attribute values like HTML+CSS does

MooseX::AttributeTree - Inherit attribute values like HTML+CSS does

This is a Git repository where development of MooseX::AttributeTree takes place. For more information, visit MooseX::AttributeTree on CPAN.

SYNOPSIS

package MyClass;
use Moose;
use MooseX::AttributeTree ();

has parent => (
  is       => 'rw',
  isa      => 'Object',
  weak_ref => 1,
);

has value => (
  is     => 'rw',
  traits => [qw/TreeInherit/],
);

DESCRIPTION

Classes can inherit attributes from their parent classes. But sometimes you want an attribute to be able to inherit its value from a parent object. For example, that's how CSS styles work in HTML.

MooseX::AttributeTree allows you to apply the TreeInherit trait to any attribute in your class. This changes the way the attribute's accessor method works. When reading the attribute's value, if no value has been set for the attribute in this object, the accessor will return the value from the parent object (which might itself be inherited).

The parent object does not need to be the same type as the child object, but it must have a method with the same name as the attribute's accessor method. (The parent's method may be an attribute accessor method, but it doesn't have to be.) If the parent doesn't have the right method, you'll get a runtime error if the child tries to call it.