Hi Niels
On Tue, Apr 2, 2024 at 8:16 PM Niels Dossche <[email protected]> wrote:
>
> On 02/04/2024 02:17, Ilija Tovilo wrote:
> > Hi everyone!
> >
> > I'd like to introduce an idea I've played around with for a couple of
> > weeks: Data classes, sometimes called structs in other languages (e.g.
> > Swift and C#).
>
> As already hinted in the thread, I also think inheritance may be dangerous in
> a first version.
> I want to add to that: if you extend a data-class with a non-data-class, the
> data-class behaviour gets lost, which is logical in a sense but also
> surprised me in a way.
Yes, that's definitely not intended. I haven't implemented any
inheritance checks yet. But if inheritance is allowed, then it should
be restricted to classes of the same kind (by-ref or by-val).
> Also, FWIW, I'm not sure about the name "data" class, perhaps "value" class
> or something alike is what people may be more familiar with wrt semantics,
> although dataclass is also a known term.
I'm happy with value class, struct, record, data class, what have you.
I'll accept whatever the majority prefers.
> I do have a question about iterator behaviour. Consider this code:
> ```
> data class Test {
> public $a = 1;
> public $b = 2;
> }
>
> $test = new Test;
> foreach ($test as $k => &$v) {
> if ($k === "b")
> $test->a = $test;
> var_dump($k);
> }
> ```
>
> This will reset the iterator of the object on separation, so we will get an
> infinite loop.
> Is this intended?
> If so, is it because the right hand side is the original object while the
> left hand side gets the clone?
> Is this consistent with how arrays separate?
That's a good question. I have not really thought about iterators yet.
Modification of an array iterated by-reference does not restart the
iterator. Actually, by-reference capturing of the value also captures
the array by-reference, which is not completely intuitive.
My initial gut feeling is to handle data classes the same, i.e.
capture them by-reference when iterating the value by reference, so
that iteration is not restarted.
Ilija
