Type::Tiny::Manual::UsingWithMouse(3) User Contributed Perl Documentation
NAME
Type::Tiny::Manual::UsingWithMouse - how to use Type::Tiny with Mouse
MANUAL
First read Type::Tiny::Manual::UsingWithMoo,
Type::Tiny::Manual::UsingWithMoo2, and
Type::Tiny::Manual::UsingWithMoo3. Everything in those parts of the
manual should work exactly the same in Mouse.
This part of the manual will focus on Mouse-specifics.
Overall, Type::Tiny is less well-tested with Mouse than it is with
Moose and Moo, but there are still a good number of test cases for
using Type::Tiny with Mouse, and there are no known major issues with
Type::Tiny's Mouse support.
Why Use Type::Tiny At All?
Mouse does have a built-in type constraint system which is fairly
convenient to use, but there are several reasons you should consider
using Type::Tiny instead.
o Type::Tiny provides helpful methods like "where" and
"plus_coercions" that allow type constraints and coercions to be
easily tweaked on a per-attribute basis.
Something like this is much harder to do with plain Mouse types:
has name => (
is => "ro",
isa => Str->plus_coercions(
ArrayRef[Str], sub { join " ", @$_ },
),
coerce => 1,
);
Mouse tends to encourage defining coercions globally, so if you
wanted one Str attribute to be able to coerce from ArrayRef[Str],
then all Str attributes would coerce from ArrayRef[Str], and they'd
all do that coercion in the same way. (Even if it might make sense
to join by a space in some places, a comma in others, and a line
break in others!)
o Type::Tiny provides automatic deep coercions, so if type Xyz has a
coercion, the following should "just work":
has xyzlist => ( is => 'ro', isa => ArrayRef[Xyz], coerce => 1 );
o Type::Tiny offers a wider selection of built-in types.
o By using Type::Tiny, you can use the same type constraints and
coercions for attributes and method parameters, in Mouse and non-
Mouse code.
Type::Utils
If you've used Mouse::Util::TypeConstraints, you may be accustomed to
using a DSL for declaring type constraints:
use Mouse::Util::TypeConstraints;
subtype 'Natural',
as 'Int',
where { $_ > 0 };
There's a module called Type::Utils that provides a very similar DSL
for declaring types in Type::Library-based type libraries.
package My::Types {
use Type::Library -base;
use Type::Utils;
use Types::Standard qw( Int );
declare 'Natural',
as Int,
where { $_ > 0 };
}
Personally I prefer the more object-oriented way to declare types
though.
In Mouse you might also declare types like this within classes and
roles too. Unlike Mouse, Type::Tiny doesn't keep types in a single
global flat namespace, so this doesn't work quite the same with
Type::Utils. It still creates the type, but it doesn't store it in any
type library; the type is returned.
package My::Class {
use Mouse;
use Type::Utils;
use Types::Standard qw( Int );
my $Natural = # store type in a variable
declare 'Natural',
as Int,
where { $_ > 0 };
has number => ( is => 'ro', isa => $Natural );
}
But really, isn't the object-oriented way cleaner?
package My::Class {
use Mouse;
use Types::Standard qw( Int );
has number => (
is => 'ro',
isa => Int->where('$_ > 0'),
);
}
Type::Tiny and MouseX::Types
Types::Standard should be a drop-in replacement for MooseX::Types. And
Types::Common::Numeric and Types::Common::String should easily replace
MouseX::Types::Common::Numeric and MouseX::Types::Common::String.
That said, if you do with to use a mixture of Type::Tiny and
MouseX::Types, they should fit together pretty seamlessly.
use Types::Standard qw( ArrayRef );
use MouseX::Types::Mouse qw( Int );
# this should just work
my $list_of_nums = ArrayRef[Int];
# and this
my $list_or_num = ArrayRef | Int;
"-mouse" Import Parameter
If you have read this far in the manual, you will know that this is the
usual way to import type constraints:
use Types::Standard qw( Int );
And the "Int" which is imported is a function that takes no arguments
and returns the Int type constraint, which is a blessed object in the
Type::Tiny class.
Type::Tiny mocks the Mouse::Meta::TypeConstraint API so well that most
Mouse and MouseX code will not be able to tell the difference.
But what if you need a real Mouse::Meta::TypeConstraint object?
use Types::Standard -mouse, qw( Int );
Now the "Int" function imported will return a genuine native Mouse type
constraint.
This flag is mostly a throwback from when Type::Tiny native objects
didn't directly work in Mouse. In 99.9% of cases, there is no reason to
use it and plenty of reasons not to. (Mouse native type constraints
don't offer helpful methods like "plus_coercions" and "where".)
"mouse_type" Method
Another quick way to get a native Mouse type constraint object from a
Type::Tiny object is to call the "mouse_type" method:
use Types::Standard qw( Int );
my $tiny_type = Int;
my $mouse_type = $tiny_type->mouse_type;
Internally, this is what the "-mouse" flag makes imported functions do.
Type::Tiny Performance
Type::Tiny should run pretty much as fast as Mouse types do. This is
because, when possible, it will use Mouse's XS implementations of type
checks to do the heavy lifting.
There are a few type constraints where Type::Tiny prefers to do things
without Mouse's help though, for consistency and correctness. For
example, the Mouse XS implementation of Bool is... strange... it
accepts blessed objects that overload "bool", but only if they return
false. If they return true, it's a type constraint error.
Using Type::Tiny instead of Mouse's type constraints shouldn't make a
significant difference to the performance of your code.
NEXT STEPS
Here's your next step:
o Type::Tiny::Manual::UsingWithMite(3)
How to use Type::Tiny(3) with Mite(3), including how to write an
entire Perl project using clean Moose-like code and no non-core
dependencies. (Not even dependencies on Mite or Type::Tiny!)
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2013-2014, 2017-2025 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.
perl v5.34.3 2025-05-03
Type::Tiny::Manual::UsingWithMouse(3)
type-tiny 2.8.2 - Generated Wed Aug 6 12:48:06 CDT 2025