NAME
    Marlin - 🐟 pretty fast class builder with most Moo/Moose features 🐟

SYNOPSIS
      use v5.20.0;
      no warnings "experimental::signatures";
  
      package Person {
        use Types::Common -lexical, -all;
        use Marlin::Util -lexical, -all;
        use Marlin
          'name!' => Str,
          'age?'  => Int,
          -strict;
    
        signature_for introduction => (
          method   => true,
          named    => [ audience => Optional[InstanceOf['Person']] ],
        );
    
        sub introduction ( $self, $arg ) {
          say "Hi " . $arg->audience . "!" if $arg->has_audience;
          say "My name is " . $self->name . ".";
        }
      }
  
      package Employee {
        use Marlin
          -base =>  [ 'Person' ],
          'employee_id!',
          -strict;
      }
  
      my $alice = Person->new( name => 'Alice Whotfia' );
  
      my $bob = Employee->new(
        name         => 'Bob Dobalina',
        employee_id  => '007',
      );
  
      $alice->introduction( audience => $bob );

DESCRIPTION
    Marlin is a fast class builder, inspired by Moose and Moo. It supports
    most of their features, but with a different syntax. Because it uses
    Class::XSAccessor, Class::XSConstructor, and Type::Tiny::XS, it is usually
    *slightly* faster though. Especially if you keep things simple and don't
    use features that force Marlin to fall back to using Pure Perl.

    It may not be as fast as classes built with the Perl builtin `class`
    syntax introduced in Perl v5.38.0, but has more features and supports Perl
    versions as old as v5.8.8. (Some features require v5.12.0+.)

    Marlin was created by the developer of Type::Tiny and Sub::HandlesVia and
    integrates with them.

  Using Marlin
    Marlin does all of its work at compile time, so doesn't export keywords
    like `has` into your namespace.

   Declaring Attributes
    Any strings found in the `use Marlin` line (except a few special ones
    beginning with a dash, used to configure Marlin) will be assumed to be
    attributes you want to declare for your class.

      package Address {
        use Marlin qw( street_address locality region country postal_code );
      }
  
      my $adr = Address->new( street_address => '123 Test Street' );
      say $adr->street_address;

    Any attributes you declare will will be accepted by the constructor that
    Marlin creates for your class, and reader/getter methods will be created
    to access their values.

    Attributes can be followed by a hashref to tailor their behaviour.

      package Address {
        use Marlin::Util qw( true false );
    
        use Marlin
          street_address  => { is => 'rw', required  => true },
          locality        => { is => 'rw' },
          region          => { is => 'rw' },
          country         => { is => 'rw', required => true },
          postal_code     => { is => 'rw', predicate => 'has_pc' },
          ;
      }
  
      my $adr = Address->new(
        street_address => '123 Test Street',
        country        => 'North Pole',
      );
  
      $adr->has_pc or die;  # will die as there is no postal_code

    Some behaviours are so commonly useful that there are shortcuts for them.

      # Shortcut for: name => { required => true }
      use Marlin 'name!';
  
      # Shortcut for: name => { predicate => true }
      use Marlin 'name?';
  
      # Shortcut for: name => { is => "rwp" }
      use Marlin 'name=';
  
      # Shortcut for: name => { is => "rw" }
      use Marlin 'name==';
  
      # Shortcut for: name => { init_arg => undef }
      use Marlin 'name.';

    Using these shortcuts, our previous Address example can be written as:

      package Address {
        use Marlin qw(
          street_address==!
          locality==
          region==
          country==!
          postal_code==?
        );
      }

    The order of these trailing modifiers doesn't matter, so 'foo=?' means the
    same as 'foo?=', though in the double-equals modifier for read-write
    attributes, the equals signs cannot have a character between them.

    There are also some useful alternatives to providing a full hashref:

      use Types::Common 'Str';
  
      # Shortcut for: name => { required => true, isa => Str }
      use Marlin 'name!' => Str;
  
      # Shortcut for: name => { lazy => true, builder => sub { ... } }
      use Marlin 'name' => sub { ... };

    If we wanted to add type checks to our previous Address example, we might
    use:

      package Address {
        use Types::Common 'Str';
        use Marlin
          'street_address==!'  => Str,
          'locality=='         => Str,
          'region=='           => Str,
          'country==!'         => Str,
          'postal_code==?'     => Str,
          ;
      }

   Supported Features for Attributes
    The following Moose/Moo-like features are supported for attributes:

    `is`
        Supports: bare, ro, rw, rwp, lazy.

    `required`
        If true, indicates that callers must provide a value for this
        attribute to the constructor. If false, indicates that it is optional.

        To indicate that the attribute is *forbidden* in the constructor, use
        a combination of `init_arg => undef` and a strict constructor.

    `init_arg`
        The name of the parameter passed to the constructor which will be used
        to populate this attribute.

        Setting to an explicit `undef` prevents constructor from even knowing
        this attribute exists. (It may still have accessors, lazy defaults,
        etc.)

    `reader`
        You can specify the name for a reader method:

          use Marlin name => { reader => "get_name" };

        If you use `reader => 1` or `reader => true`, Marlin will pick a
        default name for your reader by adding "_get" to the front of
        attributes that have a leading underscore and "get_" otherwise.

        Marlin supports a number of options to keep your accessors truly
        private. (More so than just a leading "_".)

        You can specify a scalarref variable to install the reader into:

          use Marlin name => { reader => \( my $get_name ) };
          ...
          say $thingy->$get_name();

        From Perl v5.12.0 onwards, the following is also supported:

          use Marlin name => { reader => 'my get_name' };
          ...
          say get_name( $thingy );

        From Perl v5.42.0 onwards, the following is also supported:

          use Marlin name => { reader => 'my get_name' };
          ...
          say $thingy->&get_name();

    `writer`
        Like `reader`, but a writer method.

        If you use `writer => 1` or `writer => true`, Marlin will pick a
        default name for your writer by adding "_set" to the front of
        attributes that have a leading underscore and "set_" otherwise.

        Supports the same lexical method possibilities as `reader`.

    `accessor`
        A combination reader or writer, depending on whether it's called with
        a parameter or not.

        If you use `accessor => 1` or `accessor => true`, Marlin will pick a
        default name for your writer which is just the same as your
        attribute's name.

        Supports the same lexical method possibilities as `reader`.

    `clearer`
        Like `reader`, but a clearer method.

        If you use `clearer => 1` or `clearer => true`, Marlin will pick a
        default name for your clearer by adding "_clear" to the front of
        attributes that have a leading underscore and "clear_" otherwise.

        Supports the same lexical method possibilities as `reader`.

    `predicate`
        Like `reader`, but a predicate method, checking whether a value was
        supplied for the attribute. (It checks `exists`, not `defined`!)

        If you use `predicate => 1` or `predicate => true`, Marlin will pick a
        default name for your predicate by adding "_has" to the front of
        attributes that have a leading underscore and "has_" otherwise.

        Supports the same lexical method possibilities as `reader`.

    `builder`, `default`, and `lazy`
        The `default` can be set to a coderef or a non-reference value to set
        a default value for the attribute.

        As an extension to what Moose and Moo allow, you can also set the
        default to a reference to a string of Perl code.

          default => \'[]'

        Alternatively, `builder` can be used to provide the name of a method
        to call which will generate a default value.

        If you use `builder => 1` or `builder => true`, Marlin will assume a
        builder name of "_build_" followed by your attribute name. If you use
        `builder => sub {...}` then the coderef will be installed with that
        name.

        If you choose `lazy`, then the default or builder will be run when the
        value of the attribute is first needed. Otherwise it will be run in
        the constructor.

        Currently if your class has any non-lazy builders/defaults, this will
        force the constructor to be implemented in Perl instead of XS. If you
        use lazy builders/defaults, the constructor may use XS, but the
        readers/accessors for the affected attributes will be implemented in
        Perl.

    `constant`
        Defines a constant attribute. For example:

          package Person {
            use Marlin
              ...,
              species => { constant => 'Homo sapiens' };
          }
  
          my $bob = Person->new( ... );
          say $bob->species;

        Constants attributes cannot have writers, clearers, predicates,
        builders, defaults, or triggers. They must be a simple non-reference
        value. They cannot be passed to the constructor. They *can* have a
        type constraint and coercion, which will be used *once* at compile
        time. They can have `handles` and `handles_via`, provided the
        delegated methods do not attempt to alter the constant.

        These constant attributes are still intended to be called as object
        methods. Calling them as functions is *not supported* and even though
        it might sometimes work, no guarantees are provided that it will
        continue to work.

          say $bob->species;      # GOOD
          say Person::species();  # BAD

        If you want that type of constant, use the constant pragma.

    `trigger`
        A method name or coderef to call after an attribute has been set.

        If you use `trigger => 1` or `trigger => true`, Marlin will assume a
        trigger name of "_trigger_" followed by your attribute name.

        Marlin's triggers are a little more sophisticated than Moose's: within
        the trigger, you can call the setter again without worrying about
        re-triggering the trigger.

          use v5.42.0;
  
          package Person {
            use Types::Common -types, -lexical;
            use Marlin::Util -all, -lexical;
    
            use Marlin
              first_name => {
                is      => 'rw',
                isa     => Str,
                trigger => sub ($me) { $self->clear_full_name }
              },
              last_name => {
                is      => 'rw',
                isa     => Str,
                trigger => sub ($me) { $self->clear_full_name }
              },
              full_name => {
                is      => 'lazy',
                isa     => Str,
                clearer => true,
                builder => sub ($me) { join q[ ], $me->first_name, $me->last_name }
              };
          }

        Currently if your class has any triggers, this will force the
        constructor plus the writers/accessors for the affected attributes to
        be implemented in Perl instead of XS.

        It is usually possible to design your API in ways that don't require
        triggers.

          use v5.42.0;
  
          package Person {
            use Types::Common -types, -lexical;
            use Marlin::Util -all, -lexical;
    
            use Marlin
              first_name => {
                is      => 'ro',
                isa     => Str,
                writer  => 'my set_first_name',
              },
              last_name => {
                is      => 'ro',
                isa     => Str,
                writer  => 'my set_last_name',
              },
              full_name => {
                is      => 'lazy',
                isa     => Str,
                clearer => true,
                builder => sub ($me) { join q[ ], $me->first_name, $me->last_name }
              };
    
            signature_for rename => (
              method  => true,
              named   => [ first_name => Optional[Str], last_name => Optional[Str] ],
            );
    
            sub rename ( $self, $arg ) {
              $self->&set_first_name($arg->first_name) if $arg->has_first_name;
              $self->&set_last_name($arg->last_name) if $arg->has_last_name;
              return $self;
            }
          }

    `handles` and `handles_via`.
        Method delegation.

        Supports `handles_via` like with Sub::HandlesVia.

        Lexical methods are possible here too.

          use v5.42.0;
  
          package Person {
            use Types::Common -lexical, -types;
    
            use Marlin
              name   => Str,
              emails => {
                is           => 'ro',
                isa          => ArrayRef[Str]
                default      => sub { [] },
                handles_via  => 'Array',
                handles      => [
                  'add_email'       => 'push',
                  'my find_emails'  => 'grep',
                ],
              };
    
            sub has_hotmail ( $self ) {
              my @h = $self->&find_emails( sub { /\@hotmail\./ } );
              return( @h > 0 );
            }
          }
  
          my $bob = Person->new( name => 'Bob' );
          $bob->add_email( 'bob@hotmail.example' );
          die unless $bob->has_hotmail;
  
          die if $bob->can('find_emails');  # will not die

    `isa` and `coerce`
        A type constraint for an attribute.

        Type checks do not force your constructor to be implemented in Perl,
        but type coercions do. Any type checks or coercions will force the
        accessors and writers for those attributes to be implemented in Perl.

        You can use `isa => sub { ... }` like Moo.

    `enum`
        You can use `enum => ['foo','bar']` as a shortcut for `isa =>
        Enum['foo','bar']`

    `auto_deref`
        Rarely used Moose option. If you call a reader or accessor in list
        context, will automatically apply `@{}` or `%{}` to the value if it's
        an arrayref or hashref.

    `storage`
        It is possible to give a hint to Marlin about how to store an
        attribute.

          use v5.12.0;
          use Marlin::Util -all, -lexical;
          use Types::Common -types, -lexical;
  
          package Local::User {
            use Marlin
              'username!',  => Str,
              'password!'   => {
                is            => bare,
                isa           => Str,
                writer        => 'change_password',
                required      => true,
                storage       => 'PRIVATE',
                handles_via   => 'String',
                handles       => { check_password => 'eq' },
              };
          }
  
          my $bob = Local::User->new( username => 'bd', password => 'zi1ch' );
  
          die if exists $bob->{password};   # will not die
          die if $bob->can('password');     # will not die
  
          if ( $bob->check_password( 'zi1ch' ) ) {
            ...;  # this code should execute
          }
  
          $bob->change_password( 'monk33' );

        Note that in the above example, setting `is => bare` prevents any
        reader from being created, so you cannot call `$bob->password` to
        discover his password. This would normally suffer the issue that the
        password is still stored in `$bob->{password}` if you access the
        object as a hashref.

        However, setting `storage => "PRIVATE"` tells Marlin to store the
        value privately so it no longer appears in the hashref, so won't be
        included in any Data::Dumper dumps sent to your logger, etc. This does
        complicate things if you ever need to serialize your object to a file
        or database though! (Note that while the value is not stored in the
        hashref, it is still stored *somewhere*. A determined Perl hacker can
        easily figure out where. This shouldn't be relied on in place of
        proper security.)

        Marlin supports three storage methods for attributes: "HASH" (the
        default), "PRIVATE" (as above), and "NONE" (only used for constants).

    `documentation`
        Does nothing, but you can put a string of documentation for an
        attribute here.

   Marlin Options
    Any strings passed to Marlin that have a leading dash are taking to be
    options affecting your class.

    `-base` or `-parents` or `-isa` or `-extends`
        Sets the parent classes of your class.

          package Employee {
            use Marlin -base => ['Person'], qw( employee_id payroll_number );
          }

        Marlin currently only supports inheriting from other Marlin classes,
        or from Class::XSConstructor classes. Other base classes may work,
        especially if they don't do anything much in their constructor.

        You can include version numbers:

          package Employee {
            use Marlin -base => ['Person 2.000'], ...;
          }

        If you've only got one parent class (fairly normal situation!) you can
        use a scalarref instead of an arrayref:

          package Employee {
            use Marlin -base => \'Person', qw( employee_id payroll_number );
          }

        A non-reference string is not supported:

          package Employee {
            # THIS WILL DIE
            use Marlin -base => 'Person', qw( employee_id payroll_number );
          }

    `-with` or `-roles` or `-does`
        Composes roles into your class.

          package Payable {
            use Marlin::Role -requires => ['payroll_number'];
          }
  
          package Employee {
            use Marlin
              -extends => ['Person'],
              -with    => ['Payable'],
              qw( employee_id payroll_number );
          }

        Marlin classes can accept both Marlin::Role and Role::Tiny roles.

        Like `-base`, you can include version numbers.

    `-this` or `-self` or `-class`
        Specifies the name of your class. If you don't include this, it will
        just use `caller`, which is normally what you want.

        The following are equivalent:

          package Person {
            use Marlin 'name!';
          }
  
          use Marlin -this => \'Person', 'name!';

    `-constructor`
        Tells Marlin to use a constructor name other than `new`:

          package Person {
            use Marlin -constructor => \'create', 'name!';
          }
  
          my $bob = Person->create( name => 'Bob' );

        It can sometimes be useful to name your constructor something like
        `_new` if you wish to create your own `new` method wrapping it.

    `-strict` or `-strict_constructor`
        Tells Marlin to build a constructor like MooX::StrictConstructor or
        MooseX::StrictConstructor, which will reject unknown arguments.

    `-mods` or `-modifiers`
        Exports the `before`, `after`, `around`, and `fresh` method modifiers
        from Class::Method::Modifiers, but lexical versions of them.

   Other Features
    `BUILD` and `DEMOLISH` are supported.

   Major Missing Features
    Here are some features found in Moo and Moose which are missing from
    Marlin:

    *   Support for `BUILDARGS`.

        You can work around this by naming your constructor something other
        than `new`, then wrapping it.

    *   Extensibility.

        Marlin doesn't offer any official API for building extensions.

    *   The metaobject protocol.

BUGS
    Please report any bugs to <https://github.com/tobyink/p5-marlin/issues>.

SEE ALSO
    Marlin::Role, Marlin::Util, Marlin::Manual::Principles,
    Marlin::Manual::Comparison.

    Class::XSAccessor, Class::XSConstructor, Types::Common, Type::Params, and
    Sub::HandlesVia.

    Moose and Moo.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE
    This software is copyright (c) 2025 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.

    🐟

