Role::Tiny

Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
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NAME

Role::Tiny - Roles: a nouvelle cuisine portion size slice of Moose

SYNOPSIS

 package Some::Role;

 use Role::Tiny;

 sub foo { ... }

 sub bar { ... }

 around baz => sub { ... };

 1;

elsewhere

 package Some::Class;

 use Role::Tiny::With;

 # bar gets imported, but not foo
 with 'Some::Role';

 sub foo { ... }

 # baz is wrapped in the around modifier by Class::Method::Modifiers
 sub baz { ... }

 1;

If you wanted attributes as well, look at Moo::Role.

DESCRIPTION

"Role::Tiny" is a minimalist role composition tool.

ROLE COMPOSITION

Role composition can be thought of as much more clever and meaningful multiple inheritance. The basics of this implementation of roles is:

•: If a method is already defined on a class, that method will not be composed in from the role. A method inherited by a class gets overridden by the role's method of the same name, though.
•: If a method that the role ``requires'' to be implemented is not implemented, role application will fail loudly.

Unlike Class::C3, where the last class inherited from ``wins,'' role composition is the other way around, where the class wins. If multiple roles are applied in a single call (single with statement), then if any of their provided methods clash, an exception is raised unless the class provides a method since this conflict indicates a potential problem.

ROLE METHODS

All subs created after importing Role::Tiny will be considered methods to be composed. For example:

    package MyRole;
    use List::Util qw(min);
    sub mysub { }
    use Role::Tiny;
    use List::Util qw(max);
    sub mymethod { }

In this role, "max" and "mymethod" will be included when composing MyRole, and "min" and "mysub" will not. For additional control, namespace::clean can be used to exclude undesired subs from roles.

IMPORTED SUBROUTINES

requires

 requires qw(foo bar);

Declares a list of methods that must be defined to compose role.

with

 with 'Some::Role1';

 with 'Some::Role1', 'Some::Role2';

Composes another role into the current role (or class via Role::Tiny::With).

If you have conflicts and want to resolve them in favour of Some::Role1 you can instead write:

 with 'Some::Role1';
 with 'Some::Role2';

If you have conflicts and want to resolve different conflicts in favour of different roles, please refactor your codebase.

before

 before foo => sub { ... };

See ``before method(s) => sub { ... };'' in Class::Method::Modifiers for full documentation.

Note that since you are not required to use method modifiers, Class::Method::Modifiers is lazily loaded and we do not declare it as a dependency. If your Role::Tiny role uses modifiers you must depend on both Class::Method::Modifiers and Role::Tiny.

around

 around foo => sub { ... };

See ``around method(s) => sub { ... };'' in Class::Method::Modifiers for full documentation.

after

 after foo => sub { ... };

See ``after method(s) => sub { ... };'' in Class::Method::Modifiers for full documentation.

Strict and Warnings

In addition to importing subroutines, using "Role::Tiny" applies strict and warnings to the caller.

SUBROUTINES

does_role

 if (Role::Tiny::does_role($foo, 'Some::Role')) {
   ...
 }

Returns true if class has been composed with role.

This subroutine is also installed as ->does on any class a Role::Tiny is composed into unless that class already has an ->does method, so

  if ($foo->does('Some::Role')) {
    ...
  }

will work for classes but to test a role, one must use ::does_role directly.

Additionally, Role::Tiny will override the standard Perl "DOES" method for your class. However, if "any" class in your class' inheritance hierarchy provides "DOES", then Role::Tiny will not override it.

METHODS

make_role

 Role::Tiny->make_role('Some::Role');

Makes a package into a role, but does not export any subs into it.

apply_roles_to_package

 Role::Tiny->apply_roles_to_package(
   'Some::Package', 'Some::Role', 'Some::Other::Role'
 );

Composes role with package. See also Role::Tiny::With.

apply_roles_to_object

 Role::Tiny->apply_roles_to_object($foo, qw(Some::Role1 Some::Role2));

Composes roles in order into object directly. Object is reblessed into the resulting class. Note that the object's methods get overridden by the role's ones with the same names.

create_class_with_roles

 Role::Tiny->create_class_with_roles('Some::Base', qw(Some::Role1 Some::Role2));

Creates a new class based on base, with the roles composed into it in order. New class is returned.

is_role

 Role::Tiny->is_role('Some::Role1')

Returns true if the given package is a role.

CAVEATS

•: On perl 5.8.8 and earlier, applying a role to an object won't apply any overloads from the role to other copies of the object.
•: On perl 5.16 and earlier, applying a role to a class won't apply any overloads from the role to any existing instances of the class.

AUTHOR

mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>

CONTRIBUTORS

dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>

frew - Arthur Axel ``fREW'' Schmidt (cpan:FREW) <frioux@gmail.com>

hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>

jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>

ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>

chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>

ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>

doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>

perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>

Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>

ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>

tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>

haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>

COPYRIGHT

LICENSE

This library is free software and may be distributed under the same terms as perl itself.