NAME

Types::Const - Types that coerce references to read-only

VERSION

version v0.5.0

SYNOPSIS

use Moo;
use Types::Const -types;
use Types::Standard -types;

...

has bar => (
  is      => 'ro',
  isa     => Const[ArrayRef[Str]],
  coerce  => 1,
);

DESCRIPTION

This is a type library that provides types to coerce read-only hash and array reference attributes to be deeply read-only.

See the known issues below for a discussion of side-effects.

TYPES

Const[`a]

Any defined reference value that is read-only.

If parameterized, then the referred value must also pass the type constraint, for example Const[HashRef[Int]] must a a hash reference with integer values.

It supports coercions to read-only.

This was added in v0.3.0.

KNOWN ISSUES

Side-effects of read-only data structures

A side-effect of read-only data structures is that an exception will be thrown if you attempt to fetch the value of a non-existent key:

Attempt to access disallowed key 'foo' in a restricted hash

The work around for this is to check that a key exists beforehand.

Performance issues

Validating that a complex data-structure is read-only can affect performance. If this is an issue, one workaround is to use Devel::StrictMode and only validate data structures during tests:

has bar => (
  is      => 'ro',
  isa     => STRICT ? Const[ArrayRef[Str]] : ArrayRef,
  coerce  => 1,
);

Another means of improving performance is to only check the type once. (Since it is read-only, there is no need to re-check it.)

RegexpRefs

There may be an issue with regexp references. See RT#127635.

SUPPORT FOR OLDER PERL VERSIONS

Since v0.5.0, the this module requires Perl v5.14 or later.

Future releases may only support Perl versions released in the last ten years.

If you need this module on Perl v5.10, please use one of the v0.4.x versions of this module. Significant bug or security fixes may be backported to those versions.

SEE ALSO

Const::Fast

Type::Tiny

Types::Standard

Types::ReadOnly

MooX::Const

BUGS

Please report any bugs or feature requests on the bugtracker website https://github.com/robrwo/Types-Const/issues

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

SOURCE

The development version is on github at https://github.com/robrwo/Types-Const and may be cloned from git://github.com/robrwo/Types-Const.git

AUTHOR

Robert Rothenberg rrwo@cpan.org

CONTRIBUTOR

Mohammad S Anwar mohammad.anwar@yahoo.com

COPYRIGHT AND LICENSE

This software is Copyright (c) 2018-2023 by Robert Rothenberg.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)