On Tue, Feb 18, 2025, at 17:52, Juris Evertovskis wrote:
> Hi,
>
> A recent discussion brought up the need for multiple constructors for the
> same class.
> https://externals.io/message/126428
>
> The need was mostly answered by suggestions to use factory methods.
> However on an earlier discussion it was discussed how it’s fine and even
> useful for constructor methods to violate the LSP.
> https://externals.io/message/121789
>
> I’ve felt a similar need on some projects. To have a named factory method
> that would have an overridable signature.
>
> Maybe a new keyword like `factory`that would make the method only callable
> statically? I’m thinking of something like
>
> class Triangle extends Polygon
> {
>
> public factory method fromPoints(Point $p1, Point $p2, Point $p3):
> static
> {
>
>
> // …
> }
>
>
> public factory method wrap(static|string $triangle): static
> {
>
>
> return $triangle instanceof static ? $triangle :
> static::fromWkt($triangle);
> }
> }
>
> Sure, I’m not saying this API is currently impossible. I can do the more
> narrow checks within the methods and throw from there. But sometimes it’s
> useful to precisely describe the acceptable arguments in the method signature.
>
> What do you think? Would such a feature be useless and/or harmful?
>
> BR,
> Juris
Hey Juris:
You may be interested in a super-draft RFC that I’ll propose in the next few
days… (just fixing a couple of edge cases in the implementation) it allows for
nested classes and can support what you are thinking. I will add this use case
to the RFC.
Adapting your example:
class Triangle extends Polygon {
public final class fromPoints extends Triangle {
public function __construct(Point $p1, Point $p2, Point $p3) {}
}
public final class wrap extends Triangle {
public function __construct(Triangle $triangle) {}
}
}
$triange = new Triangle::fromPoints(...$points);
I don't know if this is what you are thinking of, but it basically allows the
expression you are suggesting. If we were to implement your idea though, then
nested classes would probably be impossible (and vice-versa).
— Rob
