[swift-evolution] Dynamic Class/Struct Definition At Run Time

Xiaodi Wu xiaodi.wu at gmail.com
Wed Oct 12 08:58:57 CDT 2016

On Wed, Oct 12, 2016 at 7:47 AM, Ted F.A. van Gaalen <tedvgiosdev at gmail.com>

> On 11 Oct 2016, at 23:04, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
> Reflection is likely to be tackled in Swift 5, no?
> I'd think you don’t need reflection that much, because defining
> dynamic classes (and other entities) are solely incremental compiler
> tasks, for which it can use  previously compiled meta reference
> information (xref symbols etc).
> Imho in that perspective it is more or less independent
> of reflection. Reflection is as far as I can see is more intended to offer
> meta information at the programming level.?
> So realistically, this could be on track for Swift 6 or 7.
> As already written, there is no timeframe/deadline for this idea, it is
> just an idea,
> not a proposal (yet).
> Let's postpone discussion until then.
> Feel free to do so, but why postponing having ideas and discussing them?

The core team has requested that discussions be focused on the priorities
identified for the current phase of Swift 4. There's a sound rationale for
this request. Per Chris: "The community benefits from keeping focus on a
limited number of topics, because if there is too much going on, no one can
follow and keep track of it all. It is important for the core team to be
involved in key discussions up front. In the Swift 3 cycle, it was
problematic that many folks had no time to follow the threads until after
the review period completed."

I'm sure many people have ideas about dynamic facilities in Swift, as do we
all about other ideas, and many have been trying to be respectful of this
new proposed process. I think we can all agree that maximum participation
and the best solutions are most likely when everyone stays on the same page
with regard to the process by which we go about these discussions. No need
to postpone having ideas about Swift or talking about them with your
friends and colleagues, but let's respect the core team's urging to
postpone discussing them on this particular list for the reasons identified

In this case for instance, thinking about dynamic facilities, will
> presumably
> also influence thinking about reflection and vice versa.
> Thinking “wider” and “further” broadens the horizon of course.
> For example. what about a compiler/interpreter self improving based on
> artificial intelligence? is this 2016?
> So one can (should) do both: that is think in small steps, like discussing
> “just”  language elements and at the same time have an eye (or two) for
> the
> broader picture. If one concentrates too much on the direct path in front,
> one might
> not see other paths or what lays further ahead, which limits progress.
> ————————————————
> Let me write a small cartoon here, just intended as a little bit of humour
> just to illustrate this:
> A few thousand years ago, two very nice beings ( just returned from
> attending a
> very primitive and awkward election debate, still shivering),  looking at
> a pair
> of fairly round stone slabs with a hole in the centre.
> “What’s this ?, Why round? why the holes? Nice job, but what is it? Is it
> art?”
> “Errrrhmm, well.. I might call it ‘Wheelz', not sure yet, you can use two
> of more of them
> underneath or aside of things you’d like to move around more easily…
> with less friction, which was a hell of a drag anyway."
> The other guy walks around it, apparently deeply thinking about it.
> after some silence he says:
> “Aha… hmm.. well.. Oh, i see, yeah, yep, that’s kinda cool.. might be
> useful.
> But let’’s postpone discussing it until  ball-bearings have been invented.
>> ————————————————
> hmmm, I really have too much time… :o)
> Kind Regards
> Ted
> On Tue, Oct 11, 2016 at 15:59 David Sweeris via swift-evolution <
> swift-evolution at swift.org> wrote:
>> On Oct 11, 2016, at 12:40, Anton Zhilin via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> Hello Ted,
>> First of all, this topic belongs to reflection, which is specifically
>> stated to be out of scope of Swift 4 Phase 1. So all considerations are
>> purely theoretical for now.
>> That said, I also thought about this problem. The best I could imagine is
>> something along the following lines:
>> var builder = StructBuilder(name: "Person")
>> builder.addProperty(name: "name", type: String.self)
>> builder.addProperty(name: "age", type: Int.self)
>> builder.addComputedProperty(name: "description", getter: { (this: Any) -> String in ... })
>> builder.addComformance(CustomStringConvertible.self)let type: Any.Type = builder.build()
>> Obviously, to interact with such dynamic types and their objects, we need
>> the whole working reflection system that we don’t have right now.
>> I *think* that's only true for non-generic code, and types that aren't
>> subclasses... I think...
>> Anyway, I'm starting to wonder if some code I'm trying to write might be
>> impossible without either this feature, or some/all of the stuff from the
>> generics manifesto. So put me down as, in principle, a strong +1 (pending
>> details of the proposal when it actually gets written for Swift 10).
>> - Dave Sweeris
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
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