.. _faq:

=================================
Frequently Asked Questions (FAQs)
=================================

.. contents::
    :local:
    :depth: 1


.. _faq.rhumsaa-abandoned:

How do I fix "rhumsaa/uuid is abandoned" messages?
##################################################

When installing your project's dependencies using Composer, you might see the
following message:

.. code-block:: text

    Package rhumsaa/uuid is abandoned; you should avoid using it. Use
    ramsey/uuid instead.

Don't panic. Simply execute the following commands with Composer:

.. code-block:: bash

    composer remove rhumsaa/uuid
    composer require ramsey/uuid=^2.9

After doing so, you will have the latest ramsey/uuid package in the 2.x series,
and there will be no need to modify any code; the namespace in the 2.x series is
still ``Rhumsaa``.


.. _faq.final:

Why does ramsey/uuid use ``final``?
###################################

You might notice that many of the concrete classes returned in ramsey/uuid are
marked as ``final``. There are specific reasons for this choice, and I will
offer a few solutions for those looking to extend or mock the classes for
testing purposes.

But Why?
--------

.. raw:: html

    <div style="width:100%;height:0;padding-bottom:56%;position:relative;">
        <iframe src="https://giphy.com/embed/eauCbbW6MvqKI" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe>
    </div>
    <p><a href="https://giphy.com/gifs/eauCbbW6MvqKI">via GIPHY</a></p>

First, let's take a look at why ramsey/uuid uses ``final``.

UUIDs are defined by a set of rules --- published as `RFC 4122`_ --- and those
rules shouldn't change. If they do, then it's no longer a UUID --- at least not
as defined by `RFC 4122`_.

As an example, let's think about :php:class:`Rfc4122\\UuidV1
<Ramsey\\Uuid\\Rfc4122\\UuidV1>`. If our application wants to do something
special with this type, it might use the ``instanceof`` operator to check that a
variable is a UuidV1, or it might use a type hint on a method argument. If a
third-party library passes a UUID object to us that extends UuidV1 but
overrides some very important internal logic, then we may no longer have a
version 1 UUID. Perhaps we can all be adults and play nicely, but ramsey/uuid
cannot make any guarantees for any subclasses of UuidV1.

However, ramsey/uuid *can* make guarantees about classes that implement
:php:interface:`UuidInterface <Ramsey\\Uuid\\UuidInterface>` or
:php:interface:`Rfc4122\\UuidInterface <Ramsey\\Uuid\\Rfc4122\\UuidInterface>`.

So, if we're working with an instance of a class that is marked ``final``, we
can guarantee that the rules for the creation of that object will not change,
even if a third-party library passes us an instance of the same class.

This is the reason why ramsey/uuid specifies certain :ref:`argument and return
types <reference.types>` that are marked ``final``. Since these are ``final``,
ramsey/uuid is able to guarantee the type of data these value objects contain.
:php:class:`Type\\Integer <Ramsey\\Uuid\\Type\\Integer>` should never contain
any characters other than numeral digits, and :php:class:`Type\\Hexadecimal
<Ramsey\\Uuid\\Type\\Hexadecimal>` should never contain any characters other
than hexadecimal digits. If other libraries could extend these and return them
from UUID instances, then ramsey/uuid cannot guarantee their values.

This is very similar to using strict types with ``int``, ``float``, or ``bool``.
These types cannot change, so think of final classes in ramsey/uuid as types
that cannot change.

Overriding Behavior
-------------------

You may override the behavior of ramsey/uuid as much as you want. Despite the
use of ``final``, the library is very flexible. Take a look at the myriad
opportunities to change how the library works:

* :ref:`rfc4122.version1.random`
* :ref:`customize.timestamp-first-comb-codec`
* :ref:`customize.factory`
* :ref:`And more... <customize>`

ramsey/uuid is able to provide this flexibility through the use of `interfaces`_,
`factories`_, and `dependency injection`_.

At the same time, ramsey/uuid is able to guarantee that neither a
:php:class:`UuidV1 <Ramsey\\Uuid\\Rfc4122\\UuidV1>` nor a
:php:class:`UuidV4 <Ramsey\\Uuid\\Rfc4122\\UuidV4>` nor an
:php:class:`Integer <Ramsey\\Uuid\\Type\\Integer>` nor a
:php:class:`Time <Ramsey\\Uuid\\Type\\Time>`, etc. will ever change because of
`downstream`_ code.

UUIDs have specific rules that make them practically unique. ramsey/uuid ensures
that other code cannot change this expectation while allowing your code and
third-party libraries to change how UUIDs are generated and to return different
types of UUIDs not specified by `RFC 4122`_.

Testing With UUIDs
------------------

Sometimes, the use of ``final`` can throw a wrench in our ability to write
tests, but it doesn't have to be that way. To learn a few techniques for using
ramsey/uuid instances in your tests, take a look at :ref:`testing`.


.. _RFC 4122: https://tools.ietf.org/html/rfc4122
.. _interfaces: https://www.php.net/interfaces
.. _factories: https://en.wikipedia.org/wiki/Factory_%28object-oriented_programming%29
.. _dependency injection: https://en.wikipedia.org/wiki/Dependency_injection
.. _downstream: https://en.wikipedia.org/wiki/Downstream_(software_development)
