There are times that you want to use a role, but only as an interface. If 9
out of 10 classes use the implementation, it's annoying to have that 10th class
have to do this:
with 'My::Role' => { excludes => \...@a_long_list_of_methods };
What about something like this?
with 'My::Role' => { includes => [] };
That would be the mutually exclusive opposite of 'excludes'. No methods would
be composed into your class, but they would all be added to the 'requires'
list. This (I think) would largely overcome chromatic's objection
(http://use.perl.org/comments.pl?sid=42835&cid=68295) that if someone wants to
use a role as an interface, being forced to manually exclude every method is
annoying and would discourage role use. So a role could be trivially used as
an interface, if desired, even if implementation is provided.
Plus, if you still needed two of the 8 methods a role provided:
with 'My::Role' => { includes => [qw{ foo bar }] };
Seems to me that this is the best of both worlds, but this is also just an
offhand idea.
This also shows what I *think* is a limitation in 'excludes'. All methods
listed in a role should be explicitly added to the 'requires' list. The
following is a runtime failure:
#!/usr/bin/env perl
package My::Role;
use Moose::Role;
sub foo { __PACKAGE__ }
package Bar;
use Moose;
with 'My::Role' => { excludes => 'foo' };
print Bar->foo;
# Can't locate object method "foo" via package "Bar" at role.pl line 13.
Thoughts?
Cheers,
Ovid
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