Types::Const - Types that coerce references to read-only
use Moo; use Types::Const -types; use Types::Standard -types; ... has bar => ( is => 'ro', isa => Const[ArrayRef[Str]], coerce => 1, );
This is an experimental type library that provides types that force read-only hash and array reference attributes to be deeply read-only.
See the known issues below for a discussion of side-effects.
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.
Support for Perl versions earlier than 5.10 will be removed sometime in 2019.
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.
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.)
There may be an issue with regexp references. See RT#127635.
Bug reports and feature requests
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.
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
Robert Rothenberg firstname.lastname@example.org
Mohammad S Anwar email@example.com
COPYRIGHT AND LICENSE
This software is Copyright (c) 2018 by Robert Rothenberg.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)