[swift-evolution] Swift evolution proposal: introduce typeprivate access control level

Adrian Zubarev adrian.zubarev at devandartist.com
Fri Dec 2 09:52:32 CST 2016

Abstract classes would introduce even more awkward complexity to the current metatype model of Swift (so do I believe). Abstract classes are like existentials right? ATM we’ve got the problem with T.Type vs. T.Protocol which is clumsy. Abstract classes might introduce T.Class or even used as T.Protocol, which would be really strange.

We’re still waiting for our proposal to get re-scheduled into the evolution review to fix metatypes: Refactor Metatypes Proposal

Adrian Zubarev
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Am 2. Dezember 2016 um 16:45:03, Benjamin Spratling via swift-evolution (swift-evolution at swift.org) schrieb:

I see where you're going with that. So it's an artifact from Java and C++, too? :)

I was recently doing a review of music notation, and one of the problems is that it has multiple ways of doing exactly the same thing. Anyone trying to read a given piece of music has to learn all of them, making the problem multiple times harder than necessary.

We already have a way to enforce "you need to implement this" in Swift, and it's with protocols. Personally, I'd rather see us move in that direction.


Sent from my iPhone.

> On Dec 2, 2016, at 9:36 AM, Jeremy Pereira <jeremy.j.pereira at googlemail.com> wrote:
>> On 2 Dec 2016, at 14:07, Benjamin Spratling via swift-evolution <swift-evolution at swift.org> wrote:
>> I agree that there is a major problem with “subclasses must override these methods”. We have no capability to describe this in Swift, and frankly, it feels like something that ought to be enforced. It’s almost like we were really asked to conform to a protocol, but the protocol was a class. Maybe this is an artifact from previous Obj-C development? I.E. if it were designed in scratch in Swift it wouldn’t be a class with required overrides, but a protocol where every other method already had a default implementation?
> In Java and C++ you would implement this with an abstract method. i.e. a method that has a declaration and no body. A proposal was made to introduce these but was deferred. Reading the rationale for the decision, it looks like the dev team were generally favourable but didn’t have time to do the implementation, plus there were some details that needed to be nailed down.
> https://github.com/apple/swift-evolution/blob/master/proposals/0026-abstract-classes-and-methods.md
>>> One of the simple examples would be: you need an API that requires overriding? Make it accessible for ancestors only (even in protocols). Despite the argument "ancestors can open it to public" (there are a lot of dangerous things to do) it makes the API much more clean and hides implementation complexity. Otherwise you just have to explain it in the doc "please don't call this method, it's an internal" which feels wrong.
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