On 04/05/2016 05:13 AM, Marco Pivetta wrote:
Ad. 2. `final` means class variable (like static) or class instance
property can not change their reference, it is impossible to replace zval
in such property, in my opinion `immutable` is object behavior when using
some methods you receive newly created (cloned) object which is changed
exactly like `DateTimeImmutable`
http://php.net/manual/en/datetimeimmutable.add.php
I am aware of what `final` means in other languages, it just seems that
everyone then needs to translate back and forth from `final` to
`immutable`. In addition to that, `final` has different meaning in
inheritance (re-used keyword), so this adds to the confusion for people
unfamiliar with the feature.
There's an important point here that should not be missed. If these
values are "write once then locked', which I can definitely see as
useful, we need to have another shot at modifying them from __clone().
If not, they are effectively useless for implementing objects in the
style of DateTimeImmutable or the PSR-7 Request/Response objects.
Locking after __construct or __clone (as appropriate) is done is fine,
but if we can't clone-and-modify then I would pretty much never find
value in this feature (no pun intended).
I agree that final seems like a potentially confusing keyword, as every
other use of final (AFAIK) means "subclass cannot change this", but
that's not at all the meaning here.
Another question, which unfortunately runs straight into the previous
Properties RFC: If a public property is write-once, with the intent
being that it's set from the constructor and then cannot be overridden
but is publicly exposed... shouldn't an interface be able to declare it
as well? It makes public properties safe to use in some cases, but you
can't rely on that safely without an interface.
(Which leads to "can interfaces define properties", which leads right
back to "well what can you do with them", which leads back to the
Properties RFC. Which I still want to see happen at some point if at all
possible, as it would also subsume this question quite nicely.)
--Larry Garfield
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