Provided by: libmoosex-method-signatures-perl_0.47-1_all 
NAME
MooseX::Method::Signatures - Method declarations with type constraints and no source
filter
VERSION
version 0.47
SYNOPSIS
package Foo;
use Moose;
use MooseX::Method::Signatures;
method morning (Str $name) {
$self->say("Good morning ${name}!");
}
method hello (Str :$who, Int :$age where { $_ > 0 }) {
$self->say("Hello ${who}, I am ${age} years old!");
}
method greet (Str $name, Bool :$excited = 0) {
if ($excited) {
$self->say("GREETINGS ${name}!");
}
else {
$self->say("Hi ${name}!");
}
}
$foo->morning('Resi'); # This works.
$foo->hello(who => 'world', age => 42); # This too.
$foo->greet('Resi', excited => 1); # And this as well.
$foo->hello(who => 'world', age => 'fortytwo'); # This doesn't.
$foo->hello(who => 'world', age => -23); # This neither.
$foo->morning; # Won't work.
$foo->greet; # Will fail.
DESCRIPTION
Provides a proper method keyword, like "sub" but specifically for making methods and
validating their arguments against Moose type constraints.
SIGNATURE SYNTAX
The signature syntax is heavily based on Perl 6. However not the full Perl 6 signature
syntax is supported yet and some of it never will be.
Type Constraints
method foo ( $affe) # no type checking
method bar (Animal $affe) # $affe->isa('Animal')
method baz (Animal|Human $affe) # $affe->isa('Animal') || $affe->isa('Human')
Positional vs. Named
method foo ( $a, $b, $c) # positional
method bar (:$a, :$b, :$c) # named
method baz ( $a, $b, :$c) # combined
Required vs. Optional
method foo ($a , $b!, :$c!, :$d!) # required
method bar ($a?, $b?, :$c , :$d?) # optional
Defaults
method foo ($a = 42) # defaults to 42
Constraints
method foo ($foo where { $_ % 2 == 0 }) # only even
Invocant
method foo ( $moo) # invocant is called $self and is required
method bar ($self: $moo) # same, but explicit
method baz ($class: $moo) # invocant is called $class
Labels
method foo (: $affe ) # called as $obj->foo(affe => $value)
method bar (:apan($affe)) # called as $obj->foo(apan => $value)
Traits
method foo (Affe $bar does trait)
method foo (Affe $bar is trait)
The only currently supported trait is "coerce", which will attempt to coerce the value
provided if it doesn't satisfy the requirements of the type constraint.
Placeholders
method foo ($bar, $, $baz)
Sometimes you don't care about some parameters you're being called with. Just put the bare
sigil instead of a full variable name into the signature to avoid an extra lexical
variable to be created.
Complex Example
method foo ( SomeClass $thing where { $_->can('stuff') }:
Str $bar = "apan",
Int :$baz! = 42 where { $_ % 2 == 0 } where { $_ > 10 } )
# the invocant is called $thing, must be an instance of SomeClass and
has to implement a 'stuff' method
# $bar is positional, required, must be a string and defaults to "apan"
# $baz is named, required, must be an integer, defaults to 42 and needs
# to be even and greater than 10
BUGS, CAVEATS AND NOTES
This module is as stable now, but this is not to say that it is entirely bug free. If you
notice any odd behaviour (messages not being as good as they could for example) then
please raise a bug.
Fancy signatures
Parse::Method::Signatures is used to parse the signatures. However, some signatures that
can be parsed by it aren't supported by this module (yet).
No source filter
While this module does rely on the hairy black magic of Devel::Declare it does not depend
on a source filter. As such, it doesn't try to parse and rewrite your source code and
there should be no weird side effects.
Devel::Declare only effects compilation. After that, it's a normal subroutine. As such,
for all that hairy magic, this module is surprisingly stable.
What about regular subroutines?
Devel::Declare cannot yet change the way "sub" behaves. However, the signatures module
can. Right now it only provides very basic signatures, but it's extendable enough that
plugging MooseX::Method::Signatures signatures into that should be quite possible.
What about the return value?
Type constraints for return values can be declared using
method foo (Int $x, Str $y) returns (Bool) { ... }
however, this feature only works with scalar return values and is still considered to be
experimental.
Interaction with Moose::Role
Methods not seen by a role's "requires"
Because the processing of the MooseX::Method::Signatures "method" and the Moose "with"
keywords are both done at runtime, it can happen that a role will require a method before
it is declared (which will cause Moose to complain very loudly and abort the program).
For example, the following will not work:
# in file Canine.pm
package Canine;
use Moose;
use MooseX::Method::Signatures;
with 'Watchdog';
method bark { print "Woof!\n"; }
1;
# in file Watchdog.pm
package Watchdog;
use Moose::Role;
requires 'bark'; # will assert! evaluated before 'method' is processed
sub warn_intruder {
my $self = shift;
my $intruder = shift;
$self->bark until $intruder->gone;
}
1;
A workaround for this problem is to use "with" only after the methods have been defined.
To take our previous example, Canine could be reworked thus:
package Canine;
use Moose;
use MooseX::Method::Signatures;
method bark { print "Woof!\n"; }
with 'Watchdog';
1;
A better solution is to use MooseX::Declare instead of plain MooseX::Method::Signatures.
It defers application of roles until the end of the class definition. With it, our example
would becomes:
# in file Canine.pm
use MooseX::Declare;
class Canine with Watchdog {
method bark { print "Woof!\n"; }
}
1;
# in file Watchdog.pm
use MooseX::Declare;
role Watchdog {
requires 'bark';
method warn_intruder ( $intruder ) {
$self->bark until $intruder->gone;
}
}
1;
Subroutine redefined warnings
When composing a Moose::Role into a class that uses MooseX::Method::Signatures, you may
get a "Subroutine redefined" warning. This happens when both the role and the class define
a method/subroutine of the same name. (The way roles work, the one defined in the class
takes precedence.) To eliminate this warning, make sure that your "with" declaration
happens after any method/subroutine declarations that may have the same name as a
method/subroutine within a role.
CAVEATS
You are encouraged to read the "WARNING" in MooseX::Declare.
SEE ALSO
MooseX::Declare
Method::Signatures::Simple
Method::Signatures
Devel::Declare
Parse::Method::Signatures
Moose
signatures
AUTHOR
Florian Ragwitz <rafl@debian.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Florian Ragwitz.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.
CONTRIBUTORS
• Ash Berlin <ash@cpan.org>
• Cory Watson <gphat@cpan.org>
• Dagfinn Ilmari Mannsaaker <ilmari@ilmari.org>
• Daniel Ruoso <daniel@ruoso.com>
• Dave Rolsky <autarch@urth.org>
• Hakim Cassimally <osfameron@cpan.org>
• Jesse Luehrs <doy@tozt.net>
• Jonathan Rockway <jon@jrock.us>
• Jonathan Scott Duff <duff@pobox.com>
• Justin Hunter <justin.d.hunter@gmail.com>
• Karen Etheridge <ether@cpan.org>
• Kent Fredric <kentfredric@gmail.com>
• Lukas Mai <l.mai@web.de>
• Maik Hentsche <maik.hentsche@amd.com>
• Matt Kraai <kraai@ftbfs.org>
• Nicholas Perez <nperez@cpan.org>
• Rhesa Rozendaal <rhesa@cpan.org>
• Ricardo SIGNES <rjbs@cpan.org>
• Sebastian Willert <willert@cpan.org>
• Steffen Schwigon <ss5@renormalist.net>
• Yanick Champoux <yanick@babyl.dyndns.org>