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Man Pages


Manual Reference Pages  -  MOOSEX::METHOD::SIGNATURES (3)

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NAME

MooseX::Method::Signatures - (DEPRECATED) Method declarations with type constraints and no source filter

CONTENTS

VERSION

version 0.49

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 doesnt.

    $foo->hello(who => world, age => -23);        # This neither.

    $foo->morning;                                  # Wont 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.

DEPRECATION NOTICE

<B>Warning:B> MooseX::Method::Signatures and MooseX::Declare are based on Devel::Declare, a giant bag of crack originally implemented by mst with the goal of upsetting the perl core developers so much by its very existence that they implemented proper keyword handling in the core.

As of perl5 version 14, this goal has been achieved, and modules such as Devel::CallParser, Function::Parameters, and Keyword::Simple provide mechanisms to mangle perl syntax that don’t require hallucinogenic drugs to interpret the error messages they produce.

If you want to use declarative syntax in new code, please for the love of kittens get yourself a recent perl and look at Moops and core signatures instead.

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



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, <B>CanineB> 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.

SEE ALSO

o MooseX::Declare
o Method::Signatures::Simple
o Method::Signatures
o Devel::Declare
o Parse::Method::Signatures
o Moose
o signatures

SUPPORT

Bugs may be submitted through the RT bug tracker <https://rt.cpan.org/Public/Dist/Display.html?Name=MooseX-Method-Signatures> (or bug-MooseX-Method-Signatures@rt.cpan.org <mailto:bug-MooseX-Method-Signatures@rt.cpan.org>).

There is also a mailing list available for users of this distribution, at <http://lists.perl.org/list/moose.html>.

There is also an irc channel available for users of this distribution, at irc://irc.perl.org/#moose.

I am also usually active on irc, as ’ether’ at irc.perl.org.

AUTHOR

Florian Ragwitz <rafl@debian.org>

CONTRIBUTORS

o Karen Etheridge <ether@cpan.org>
o Ash Berlin <ash@cpan.org>
o Daniel Ruoso <daniel@ruoso.com>
o Justin Hunter <justin.d.hunter@gmail.com>
o Nicholas Perez <nperez@cpan.org>
o Dagfinn Ilmari Mannsaaker <ilmari@ilmari.org>
o Rhesa Rozendaal <rhesa@cpan.org>
o Yanick Champoux <yanick@babyl.dyndns.org>
o Cory Watson <gphat@cpan.org>
o Kent Fredric <kentfredric@gmail.com>
o Lukas Mai <l.mai@web.de>
o Matt Kraai <kraai@ftbfs.org>
o Jonathan Scott Duff <duff@pobox.com>
o Jesse Luehrs <doy@tozt.net>
o Hakim Cassimally <osfameron@cpan.org>
o Dave Rolsky <autarch@urth.org>
o Ricardo SIGNES <rjbs@cpan.org>
o Sebastian Willert <willert@cpan.org>
o Steffen Schwigon <ss5@renormalist.net>

COPYRIGHT AND LICENCE

This software is copyright (c) 2008 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.

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