Exploring Type::Tiny Part 6: Some Interesting Type Libraries

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Type::Tiny is probably best known as a way of having Moose-like type constraints in Moo, but it can be used for so much more. This is the sixth in a series of posts showing other things you can use Type::Tiny for. This article along with the earlier ones in the series can be found on my blog and in the Cool Uses for Perl section of PerlMonks.

While Types::Standard provides all the type constraints Moose users will be familiar with (and a few more) there are other type libraries you can use instead of or as well as Types::Standard.


If your attribute or parameter needs to accept a file or directory name, I’d strongly recommend using Types::Path::Tiny. It provides Path, File, and Dir types, plus Abs* versions of them which coerce given filenames into absolute paths. The Path::Tiny objects it coerces strings into provide a bunch of helpful methods for manipulating files.

   package MyApp::Config {
      use Moo;
      use Types::Path::Tiny qw(AbsFile);
      use JSON::MaybeXS qw(decode_json);
      has config_file => (
         is      => 'ro',
         isa     => AbsFile->where(q{ $_->basename =~ q/\.json$/ }),
         coerce  => 1,
      sub get_hash {
         my $self = shift;
         decode_json( $self->config_file->slurp_utf8 );

Nice? Types::Path::Tiny is my personal favourite third-party type library. If you’re writing an application that needs to deal with files, use it.

Types::Common::String and Types::Common::Numeric

Types::Common::String provides a bunch of type constraints more specific than the standard Str type. If you have indicated that an attribute or parameter should be a string, it’s pretty rare that you really want to allow any string. You might want to constrain it more. This type library has types like NonEmptyStr and UpperCaseStr.

Types::Common::Numeric does the same for numbers, giving you type constraints like PositiveInt and IntRange[1,10].

Both of these libraries come bundled with Type::Tiny, so if you’re already using Types::Standard, won’t add any extra dependencies to your code.


This is a type library created for Type::Tiny’s internal use and gives you types like ArrayLike, HashLike, and CodeLike which allow overloaded objects.

Again it’s bundled with Type::Tiny, so won’t add any extra dependencies.


A type library for DateTime objects, allowing them to be coerced from strings.

   has start_date => (
      is      => 'ro',
      isa     => DateTimeUTC,
      coerce  => 1,

The above will not only coerce the attribute to a DateTime object, but coerce it to the correct timezone.