Re: Final properties

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