NAME

Type::Alias - type alias for type constraints

SYNOPSIS

use Types::Standard -types;
use Type::Alias
    -alias => [qw(ID User Guest LoginUser UserList)],
    -fun => [qw(List)];

type ID => Str;

type LoginUser => {
    _type => 'LoginUser',
    id   => ID,
    name => Str,
    age  => Int,
};

type Guest => {
    _type => 'Guest',
    name => Str,
};

type User => LoginUser | Guest;

type List => sub {
    my ($R) = @_;
    $R ? ArrayRef[$R] : ArrayRef;
};

type UserList => List[User];

UserList->check([
    { _type => 'LoginUser', id => '1', name => 'foo', age => 20 },
    { _type => 'Guest', name => 'bar' },
]); # => OK

# Internally UserList is equivalent to the following type:
#
# ArrayRef[
#     Dict[
#         _type => Eq['LoginUser'],
#         age => Int,
#         id => Str,
#         name => Str
#     ] |
#     Dict[
#         _type => Eq['Guest'],
#         name => Str
#     ]
# ]

DESCRIPTION

Type::Alias creates type aliases and type functions for existing type constraints such as Type::Tiny, Moose, Mouse. The aim of this module is to enhance the reusability of types and make it easier to express types.

IMPORT OPTIONS

-alias

-alias is an array reference that defines type aliases. The default is [].

use Type::Alias -alias => [qw(ID User)];

type ID => Str;

type User => {
    id   => ID,
    name => Str,
    age  => Int,
};

-fun

-fun is an array reference that defines type functions. The default is [].

use Type::Alias -fun => [qw(List)];

type List => sub($R) {
   $R ? ArrayRef[$R] : ArrayRef;
};

type

The type option is used to configure the type function that defines type aliases and type functions.

# Rename type function:
use Type::Alias type => { -as => 'mytype' };

mytype ID => Str; # declare type alias

EXPORTED FUNCTIONS

type($alias_name, $type_args)

type is a function that defines a type alias and a type function. It recursively generates type constraints based on $type_args.

$type_args is a type constraint

Given a type constraint in $type_args, it returns the type constraint as is. Type::Alias treats objects with check and get_message methods as type constraints.

type ID => Str;

ID->check('foo'); # OK

Internally ID is equivalent to the following type:

sub ID() { Str }

$type_args is an undefined value

Given a undefined value in $type_args, it returns the type constraint defined by Type::Tiny's Undef type.

type Foo => Undef;

Foo->check(undef); # OK

Internally Foo is equivalent to the following type:

sub Foo() { Undef }

$type_args is a string value

Given a string value in $type_args, it returns the type constraint defined by Types::Equal::Eq type.

type ID => 'foo';

ID->check('foo'); # OK

type Published => 'published';
type Draft => 'draft';
type Status => Published | Draft;

Status->check('published'); # ok
Status->check('draft'); # ok

Internally Status is equivalent to the following type:

sub Status() { Eq['published'] | Eq['draft'] }

$type_args is a number value

Available at v5.36 above. Less than v5.36, converts to Eq.

Given a number value in $type_args, it returns the type constraint defined by Types::Equal::NumEq type.

type Foo => 123;
# Foo is NumEq[123]; v5.36 above
# Foo is Eq[123]; # less than v5.36

$type_args is a boolean value

Available at v5.36 above. Less than v5.36, converts to Eq.

Given a boolean value in $type_args, it returns the type constraint defined by Type::Tiny's Bool type.

type Foo => !!1;
# Foo is Type::Alias::True; v5.36 above
# Foo is Eq[!!1]; # less than v5.36

$type_args is a hash reference

Given a hash reference in $type_args, it returns the type constraint defined by Type::Tiny's Dict type.

type Point => {
    x => Int,
    y => Int,
};

Point->check({
    x => 1,
    y => 2
}); # OK

Internally Point is equivalent to the following type:

sub Point() { Dict[x=>Int,y=>Int] }

$type_args is an array reference

Given an array reference in $type_args, it returns the type constraint defined by Type::Tiny's Tuple type.

type Option => [Str, Int];

Option->check('foo', 1); # OK

Internally Option is equivalent to the following type:

sub Option() { Tuple[Str,Int] }

$type_args is a code reference

Given a code reference in $type_args, it defines a type function that accepts a type constraint as an argument and returns the type constraint.

type List => sub($R) {
   $R ? ArrayRef[$R] : ArrayRef;
};

type Points => List[{ x => Int, y => Int }];

Points->check([
    { x => 1, y => 2 },
    { x => 3, y => 4 },
]); # OK

Internally List is equivalent to the following type:

sub List :prototype(;$) {
   my @args = map { Type::Alias::to_type($_) } @{$_[0]};

    sub($R) {
       $R ? ArrayRef[$R] : ArrayRef;
    }->(@args);
}

And Points is equivalent to the following type:

sub Points() { List[Dict[x=>Int,y=>Int]] }

COOKBOOK

Exporter

Type::Alias is designed to be used with Exporter. The following is an example of using Type::Alias with Exporter.

package MyService {

    use Exporter 'import';
    our @EXPORT_OK = qw(hello Message);

    use Type::Alias -alias => [qw(Message)];
    use Types::Common -types;

    type Message => StrLength[1, 100];

    sub hello { ... }
}

package MyApp {

    use MyService qw(Message);
    Message->check('World!');
}

Class builders

Type::Alias is designed to be used with class builders such as Moose, Moo and Mouse.

package Sample {
    use Moose;

    use Exporter 'import';
    our @EXPORT_OK = qw( UserName );

    use Type::Alias -alias => [qw( UserName )];
    use Types::Standard qw( Str );

    type UserName => Str & sub { length $_ > 1 };

    has 'name' => (is => 'rw', isa => UserName);
}

package MyApp {

    use Sample qw( UserName );

    my $sample = Sample->new(name => 'hello');
    $sample->hello; # => 'hello'
    $sample->hello(''); # ERROR!

    UserName->check('hello'); # OK
}

Validation modules

Type::Alias is designed to be used with validation modules such as Type::Params, Smart::Args::TypeTiny and Data::Validator:

use Type::Alias -alias => [qw( Message )];
use Types::Standard qw( Str );
use Type::Params -sigs;

type Message => Str & sub { length($_) > 1 };

signature_for hello => (
    positional => [ Message ],
);

sub hello {
    my ($message) = @_;
    return "HELLO " . $message;
}

hello('World') # => 'HELLO World';
hello('') # => Error!

NOTE

Function::Parameters works using type aliases from outside.

package Sample {

    use Exporter 'import';
    our @EXPORT_OK = qw(User);

    use Type::Alias -alias => [qw(User)];
    use Types::Standard -types;

    type User => {
        name => Str,
    };
}

use Types::Standard -types;
use Function::Parameters;

use Sample qw(User);

fun hello (User $user) {
    return "Hello, $user->{name}!";
}

hello({ name => 'foo' }) # => 'Hello, foo!';

However, if you write a type alias inline as follows, the current implementation will not work.

use Type::Alias -alias => [qw(Gorilla)];

type Gorilla => Dict[ name => Str ];

fun ooh(Gorilla $user) { # => ERROR: type Gorilla is not defined at compile time
    return "ooh ooh, $user->{name}!";
}

ooh({ name => 'gorilla' }) # => 'ooh ooh, gorilla!';

SEE ALSO

Type::Tiny

LICENSE

Copyright (C) kobaken.

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

AUTHOR

kobaken kfly@cpan.org