NAME
    MooX::Struct - make simple lightweight record-like structures that make
    sounds like cows

SYNOPSIS
     use MooX::Struct
        Point   => [ 'x', 'y' ],
        Point3D => [ -extends => ['Point'], 'z' ],
     ;
 
     my $origin = Point3D->new( x => 0, y => 0, z => 0 );
 
     # or...
     my $origin = Point3D[ 0, 0, 0 ];

DESCRIPTION
    MooX::Struct allows you to create cheap struct-like classes for your
    data using Moo.

    While similar in spirit to MooseX::Struct and Class::Struct,
    MooX::Struct has a somewhat different usage pattern. Rather than
    providing you with a "struct" keyword which can be used to define
    structs, you define all the structs as part of the "use" statement. This
    means they happen at compile time.

    A struct is just an "anonymous" Moo class. MooX::Struct creates this
    class for you, and installs a lexical alias for it in your namespace.
    Thus your module can create a "Point3D" struct, and some other module
    can too, and they won't interfere with each other. All struct classes
    inherit from MooX::Struct.

    Arguments for MooX::Struct are key-value pairs, where keys are the
    struct names, and values are arrayrefs.

     use MooX::Struct
        Person   => [qw/ name address /],
        Company  => [qw/ name address registration_number /];

    The elements in the array are the attributes for the struct (which will
    be created as read-only attributes), however certain array elements are
    treated specially.

    *   As per the example in the "SYNOPSIS", "-extends" introduces a list
        of parent classes for the struct. If not specified, then classes
        inherit from MooX::Struct itself.

        Structs can inherit from other structs, or from normal classes. If
        inheriting from another struct, then you *must* define both in the
        same "use" statement. Inheriting from a non-struct class is
        discouraged.

         # Not like this.
         use MooX::Struct Point   => [ 'x', 'y' ];
         use MooX::Struct Point3D => [ -extends => ['Point'], 'z' ];
 
         # Like this.
         use MooX::Struct
            Point   => [ 'x', 'y' ],
            Point3D => [ -extends => ['Point'], 'z' ],
         ;

    *   Similarly "-with" consumes a list of roles.

    *   If an attribute name is followed by a coderef, this is installed as
        a method instead.

         use MooX::Struct
            Person => [
               qw( name age sex ),
               greet => sub {
                  my $self = shift;
                  CORE::say "Hello ", $self->name;
               },
            ];

        But if you're defining methods for your structs, then you've
        possibly missed the point of them.

    *   If an attribute name is followed by an arrayref, these are used to
        set the options for the attribute. For example:

         use MooX::Struct
            Person  => [ name => [ is => 'ro', required => 1 ] ];

        Using the "init_arg" option would probably break stuff. Don't do
        that.

    *   Attribute names may be "decorated" with prefix and postfix "sigils".
        The prefix sigils of "@" and "%" specify that the attribute isa
        arrayref or hashref respectively. (Blessed arrayrefs and hashrefs
        are accepted; as are objects which overload "@{}" and "%{}".) The
        prefix sigil "$" specifies that the attribute value must not be an
        unblessed arrayref or hashref. The prefix sigil "+" indicates the
        attribute is a number, and provides a default value of 0, unless the
        attribute is required. The postfix sigil "!" specifies that the
        attribute is required.

         use MooX::Struct
            Person  => [qw( $name! @children )];

         Person->new();         # dies, name is required
         Person->new(           # dies, children should be arrayref
            name     => 'Bob',
            children => 2,
         );

    Prior to the key-value list, some additional flags can be given. These
    begin with hyphens. The flag "-rw" indicates that attributes should be
    read-write rather than read-only.

     use MooX::Struct -rw,
        Person => [
           qw( name age sex ),
           greet => sub {
              my $self = shift;
              CORE::say "Hello ", $self->name;
           },
        ];

    The "-retain" flag can be used to indicate that MooX::Struct should not
    use namespace::clean to enforce lexicalness on your struct class
    aliases.

    Flags "-trace" and "-deparse" may be of use debugging.

  Instantiating Structs
    There are two supported methods of instatiating structs. You can use a
    traditional class-like constructor with named parameters:

     my $point = Point->new( x => 1, y => 2 );

    Or you can use the abbreviated syntax with positional parameters:

     my $point = Point[ 1, 2 ];

    If you know about Moo and peek around in the source code for this
    module, then I'm sure you can figure out additional ways to instantiate
    them, but the above are the only supported two.

    When inheritance or roles have been used, it might not always be clear
    what order the positional parameters come in (though see the
    documentation for the "FIELDS" below), so the traditional class-like
    style may be preferred.

  Methods
    Structs are objects and thus have methods. You can define your own
    methods as described above. MooX::Struct's built-in methods will always
    obey the convention of being in ALL CAPS (except in the case of
    "_data_printer"). By using lower-case letters to name your own methods,
    you can avoid naming collisions.

    The following methods are currently defined. Additionally all the
    standard Perl ("isa", "can", etc) and Moo ("new", "does", etc) methods
    are available.

    "OBJECT_ID"
        Returns a unique identifier for the object.

    "FIELDS"
        Returns a list of fields associated with the object. For the
        "Point3D" struct in the SYNPOSIS, this would be 'x', 'y', 'z'.

        The order the fields are returned in is equal to the order they must
        be supplied for the positional constructor.

    "TYPE"
        Returns the type name of the struct, e.g. 'Point3D'.

    "TO_HASH"
        Returns a reference to an unblessed hash where the object's fields
        are the keys and the object's values are the hash values.

    "TO_ARRAY"
        Returns a reference to an unblessed array where the object's values
        are the array items, in the same order as listed by "FIELDS".

    "TO_STRING"
        Joins "TO_ARRAY" with whitespace. This is not necessarily a
        brilliant stringification, but easy enough to overload:

         use MooX::Struct
            Point => [
               qw( x y ),
               TO_STRING => sub {
                  sprintf "(%d, %d)"), $_[0]->x, $_[0]->y;
               },
            ]
         ;

    "CLONE"
        Creates a shallow clone of the object.

    "EXTEND"
        An exverimental feature.

        Extend a class or object with additional attributes, methods, etc.
        This method takes almost all the same arguments as "use
        MooX::Struct", albeit with some slight differences.

         use MooX::Struct Point => [qw/ +x +y /];
         my $point = Point[2, 3];
         $point->EXTEND(-rw, q/+z/);  # extend an object
         $point->can('z');   # true
 
         my $new_class = Point->EXTEND('+z');  # extend a class
         my $point_3d  = $new_class->new( x => 1, y => 2, z => 3 );
         $point_3d->TYPE;  # Point !
 
         my $point_4d = $new_class->EXTEND(\"Point4D", '+t');
         $point_4d->TYPE;  # Point4D
 
         my $origin = Point[]->EXTEND(-with => [qw/ Math::Role::Origin /]);

        This feature has been included mostly because it's easy to implement
        on top of the existing code for processing "use MooX::Struct". Some
        subsets of this functionality are sane, such as the ability to add
        traits to an object. Others (like the ability to add a new
        uninitialized, read-only attribute to an existing object) are less
        sensible.

    "BUILDARGS"
        Moo internal fu.

    "_data_printer"
        Automatic pretty printing with Data::Printer.

         use Data::Printer;
         use MooX::Struct Point => [qw/ +x +y /];
         my $origin = Point[];
         p $origin;

    With the exception of "FIELDS" and "TYPE", any of these can be
    overridden using the standard way of specifying methods for structs.

  Overloading
    MooX::Struct overloads stringification and array dereferencing. Objects
    always evaluate to true in a boolean context. (Even if they stringify to
    the empty string.)

BUGS
    Please report any bugs to
    <http://rt.cpan.org/Dist/Display.html?Queue=MooX-Struct>.

SEE ALSO
    Moo, MooX::Struct::Util, MooseX::Struct, Class::Struct.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE
    This software is copyright (c) 2012 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.

