# phpman > perldoc > Type::Registry

## NAME
    [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown) - a glorified hashref for looking up type constraints

## SYNOPSIS
       package [Foo::Bar](https://www.chedong.com/phpMan.php/perldoc/Foo%3A%3ABar/markdown);

       use [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown);

       my $reg = "[Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown)"->for_me;  # a registry for [Foo::Bar](https://www.chedong.com/phpMan.php/perldoc/Foo%3A%3ABar/markdown)

       # Register all types from [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown)
       $reg->add_types(-Standard);

       # Register just one type from [Types::XSD](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AXSD/markdown)
       $reg->add_types(-XSD => ["NonNegativeInteger"]);

       # Register all types from [MyApp::Types](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ATypes/markdown)
       $reg->add_types("[MyApp::Types](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ATypes/markdown)");

       # Create a type alias
       $reg->alias_type("NonNegativeInteger" => "Count");

       # Look up a type constraint
       my $type = $reg->lookup("ArrayRef[Count]");

       $type->check([1, 2, 3.14159]);  # croaks

    Alternatively:

       package [Foo::Bar](https://www.chedong.com/phpMan.php/perldoc/Foo%3A%3ABar/markdown);

       use [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown) qw( t );

       # Register all types from [Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown)
       t->add_types(-Standard);

       # Register just one type from [Types::XSD](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AXSD/markdown)
       t->add_types(-XSD => ["NonNegativeInteger"]);

       # Register all types from [MyApp::Types](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ATypes/markdown)
       t->add_types("[MyApp::Types](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ATypes/markdown)");

       # Create a type alias
       t->alias_type("NonNegativeInteger" => "Count");

       # Look up a type constraint
       my $type = t("ArrayRef[Count]");

       $type->check([1, 2, 3.14159]);  # croaks

## STATUS
    This module is covered by the Type-Tiny stability policy.

## DESCRIPTION
    A type registry is basically just a hashref mapping type names to type constraint objects.

### Constructors
    "new"
        Create a new glorified hashref.

    "for_class($class)"
        Create or return the existing glorified hashref associated with the given class.

        Note that any type constraint you have imported from [Type::Library](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ALibrary/markdown)-based type libraries will
        be automatically available in your class' registry.

    "for_me"
        Create or return the existing glorified hashref associated with the caller.

### Methods
    "add_types(@libraries)"
        The libraries list is treated as an "optlist" (a la [Data::OptList](https://www.chedong.com/phpMan.php/perldoc/Data%3A%3AOptList/markdown)).

        Strings are the names of type libraries; if the first character is a hyphen, it is expanded
        to the "Types::" prefix. If followed by an arrayref, this is the list of types to import
        from that library. Otherwise, imports all types from the library.

           use [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown) qw(t);

           t->add_types(-Standard);  # OR: t->add_types("[Types::Standard](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3AStandard/markdown)");

           t->add_types(
              -TypeTiny => ['HashLike'],
              -Standard => ['HashRef' => { -as => 'RealHash' }],
           );

        [MooseX::Types](https://www.chedong.com/phpMan.php/perldoc/MooseX%3A%3ATypes/markdown) (and experimentally, [MouseX::Types](https://www.chedong.com/phpMan.php/perldoc/MouseX%3A%3ATypes/markdown)) libraries can also be added this way, but
        *cannot be followed by an arrayref of types to import*.

    "add_type($type, $name)"
        The long-awaited singular form of "add_types". Given a type constraint object, adds it to
        the registry with a given name. The name may be omitted, in which case "$type->name" is
        called, and [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown) will throw an error if $type is anonymous. If a name is
        explicitly given, [Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown) cares not one wit whether the type constraint is anonymous.

        This method can even add [MooseX::Types](https://www.chedong.com/phpMan.php/perldoc/MooseX%3A%3ATypes/markdown) and [MouseX::Types](https://www.chedong.com/phpMan.php/perldoc/MouseX%3A%3ATypes/markdown) type constraints; indeed anything
        that can be handled by [Types::TypeTiny](https://www.chedong.com/phpMan.php/perldoc/Types%3A%3ATypeTiny/markdown)'s "to_TypeTiny" function. (Bear in mind that
        to_TypeTiny *always* results in an anonymous type constraint, so $name will be required.)

    "alias_type($oldname, $newname)"
        Create an alias for an existing type.

    "simple_lookup($name)"
        Look up a type in the registry by name.

        Returns undef if not found.

    "foreign_lookup($name)"
        Like "simple_lookup", but if the type name contains "::", will attempt to load it from a
        type library. (And will attempt to load that module.)

    "lookup($name)"
        Look up by name, with a DSL.

           t->lookup("Int|ArrayRef[Int]")

        The DSL can be summed up as:

           X               type from this registry
           [My::Lib::X](https://www.chedong.com/phpMan.php/perldoc/My%3A%3ALib%3A%3AX/markdown)      type from a type library
           ~X              complementary type
           X | Y           union
           X & Y           intersection
           X[...]          parameterized type
           slurpy X        slurpy type
           [Foo::Bar](https://www.chedong.com/phpMan.php/perldoc/Foo%3A%3ABar/markdown)::      class type

        Croaks if not found.

    "make_union(@constraints)", "make_intersection(@constraints)", "make_class_type($class)",
    "make_role_type($role)"
        Convenience methods for creating certain common type constraints.

    "AUTOLOAD"
        Overloaded to call "lookup".

           $registry->Str;  # like $registry->lookup("Str")

    "get_parent", "set_parent($reg)", "clear_parent", "has_parent"
        Advanced stuff. Allows a registry to have a "parent" registry which it inherits type
        constraints from.

### Functions
    "t" This class can export a function "t" which acts like
        ""[Type::Registry](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ARegistry/markdown)"->for_class($importing_class)".

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

## SEE ALSO
    [Type::Library](https://www.chedong.com/phpMan.php/perldoc/Type%3A%3ALibrary/markdown).

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

## COPYRIGHT AND LICENCE
    This software is copyright (c) 2013-2014, 2017-2021 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.