Fitz,
I am not sure when that behavior will change so a TODO test is
probably still very premature.
I think docs would be better placed in Moose where we discuss the
alias and exclude features of roles. Patches are always welcome.
- Stevan
On May 31, 2009, at 2:02 PM, Fitz Elliott wrote:
Hello All,
I have a Role that uses MooseX::AttributeHelpers to provide
convenience methods for its attributes. I ran into a problem when
I tried to alias the provided methods in the composing class. Here
is the example code:
package DoesFetch;
use Moose::Role;
use MooseX::AttributeHelpers;
has 'queued' => (
metaclass => 'Collection::Array',
is => 'ro',
isa => 'ArrayRef[Int]',
default => sub { [] },
provides => {push => 'add_ids'},
);
package Source::Pubmed;
use Moose;
with 'DoesFetch' => {alias => {add_ids => 'add_pmids',}};
package main;
my $source = Source::Pubmed->new();
$source->add_ids(1..10); # works
$source->add_pmids(11..20); # dies: Can't locate object method
# "add_pmids" via package
"Source::Pubmed"
I've worked around this by adding a wrapper sub to Source::Pubmed,
but I was curious as to why this didn't work. After doing some
debugging, I found that 'add_ids' was being installed in
Source::Pubmed's namespace, but not DoesFetch's. The aliasing code
in Moose::Meta::Role::Application::ToClass gets the methods from the
Role and DoesFetch doesn't know that 'add_ids' is one of its methods.
In the perldoc for Moose::Meta::Role, under "Attributes", it says:
"However, attributes stored in this class are not stored as
objects. Rather, the attribute definition is stored as a hash
reference. When a role is composed into a class, this hash reference
is passed directly to the metaclass's add_attribute method."
"This is quite likely to change in the future."
(http://search.cpan.org/~drolsky/Moose-0.79/lib/Moose/Meta/Role.pm#Attributes
)
I'm assuming from this that MX::AttributeHelpers runs when the
attributes are inflated, and therefore can't install its methods
into the Role. Is that correct? Would it be helpful if I were to
provide a note for the MX::AttributeHelpers docs that warns about
this usage? I can also provide a TODO test, if this behavior is
still expected to change.
Thanks everyone, for such a fantastic module!
Cheers,
Fitz
