# Type::Tiny::Manual::UsingWithClassTiny - use of Type::Tiny with Class::... - perldoc - [phpMan]

## NAME
    [Type::Tiny::Manual::UsingWithClassTiny](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ATiny%3A%3AManual%3A%3AUsingWithClassTiny/markdown) - use of [Type::Tiny](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ATiny/markdown) with [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown)

## MANUAL
    [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown) is an even-smaller-than-Moo class builder.

    Let's translate the classic Horse class from Moo to [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown).

    Moo:

      package Horse {
        use Moo;
        use [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown) qw( Str Num ArrayRef );
        use [namespace::autoclean](https://www.chedong.com/phpMan.php/perldoc/namespace%3A%3Aautoclean/markdown);

        has name       => ( is => 'ro', isa => Str, required => 1 );
        has gender     => ( is => 'ro', isa => Str );
        has age        => ( is => 'rw', isa => Num );
        has children   => (
          is       => 'ro',
          isa      => ArrayRef,
          default  => sub { return [] },
        );
      }

    [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown):

      package Horse {
        use [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown) qw( gender age ), {
          name     => sub { die "name is required"; },
          children => sub { return [] },
        };
        use [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown) qw( Str Num ArrayRef Dict Optional Slurpy Any Object );
        use [Type::Params](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3AParams/markdown) qw( signature_for );
        use [namespace::autoclean](https://www.chedong.com/phpMan.php/perldoc/namespace%3A%3Aautoclean/markdown);

        # type checks
        signature_for BUILD => (
          method => Object,
          named  => [
            name       => Str,
            gender     => Optional[Str],
            age        => Optional[Num],
            children   => Optional[ArrayRef],
            ()         => Slurpy[Any],
          ],
          fallback => 1,
        );
        signature_for [ 'name', 'gender', 'children' ] => (
          method     => Object,
          positional => [],
        );
        signature_for age => (
          method     => Object,
          positional => [ Optional[Num] ],
        );
      }

    What's going on here?

    Well, [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown), after it has built a new object, will do this:

      $self->BUILD($args);

    (Technically, it calls "BUILD" not just for the current class, but for all parent classes too.)
    We can hook onto this in order to check type constraints for the constructor.

    We use "signature_for" from [Type::Params](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3AParams/markdown) to wrap the original "BUILD" method (which doesn't
    exist, so "fallback => 1" will just assume an empty sub) with a type check for its arguments.
    The type check is just a Dict that checks the class's required and optional attributes and
    includes Slurpy[Any] at the end to be flexible for subclasses adding new attributes.

    Then we wrap the "name", "gender", and "children" methods with checks to make sure they're only
    being called as getters, and we wrap "age", allowing it to be called as a setter with a Num.

    There are also a couple of CPAN modules that can help you out.

### [Class::Tiny::ConstrainedAccessor](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AConstrainedAccessor/markdown)
    [Class::Tiny::ConstrainedAccessor](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AConstrainedAccessor/markdown) creates a "BUILD" and accessors that enforce [Type::Tiny](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ATiny/markdown)
    constraints. Attribute types are passed to [Class::Tiny::ConstrainedAccessor](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AConstrainedAccessor/markdown); attribute defaults
    are passed to [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown).

      package Horse {
        use [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown) qw( Str Num ArrayRef );
        use [Class::Tiny::ConstrainedAccessor](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AConstrainedAccessor/markdown) {
          name     => Str,
          gender   => Str,
          age      => Num,
          children => ArrayRef,
        };
        use [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown) qw( gender age ), {
          name     => sub { die "name is required"; },
          children => sub { return [] },
        };
      }

### [Class::Tiny::Antlers](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AAntlers/markdown)
    [Class::Tiny::Antlers](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AAntlers/markdown) provides Moose-like syntax for [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown), including support for "isa".
    You do not also need to use [Class::Tiny](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny/markdown) itself.

      package Horse {
        use [Class::Tiny::Antlers](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3ATiny%3A%3AAntlers/markdown) qw(has);
        use [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown) qw( Str Num ArrayRef );
        use [namespace::autoclean](https://www.chedong.com/phpMan.php/perldoc/namespace%3A%3Aautoclean/markdown);

        has name       => (
          is        => 'ro',
          isa       => Str,
          default   => sub { die "name is required" },
        );
        has gender     => ( is => 'ro',    isa => Str );
        has age        => ( is => 'rw',    isa => Num );
        has children   => (
          is        => 'ro',
          isa       => ArrayRef,
          default   => sub { return [] },
        );
      }

## NEXT STEPS
    Here's your next step:

    *   [Type::Tiny::Manual::UsingWithOther](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ATiny%3A%3AManual%3A%3AUsingWithOther/markdown)

        Using [Type::Tiny](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ATiny/markdown) with [Class::InsideOut](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3AInsideOut/markdown), [Params::Check](https://www.chedong.com/phpMan.php/perldoc/Params%3A%3ACheck/markdown), and [Object::Accessor](https://www.chedong.com/phpMan.php/perldoc/Object%3A%3AAccessor/markdown).

## AUTHOR
    Toby Inkster <<tobyink@cpan.org>>.

## COPYRIGHT AND LICENCE
    This software is copyright (c) 2013-2014, 2017-2023 by Toby Inkster.

    This is free software; you can redistribute it and/or modify it under the same terms as the Perl
    5 programming language system itself.

## DISCLAIMER OF WARRANTIES
    THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
    WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
    PURPOSE.