[swift-evolution] Mutability for Foundation types in Swift

[Tony Parker]

Hi Jose,

> On Apr 22, 2016, at 2:53 PM, Jose Cheyo Jimenez <cheyo at masters3d.com> wrote:
> 
> Hi Tony, 
> 
> Would value types like NSDateFormatterStyle or NSCalendarUnit etc get renamed with out `NS` in Swift ?
> 

This, we are still iterating on in our team. I hope to have an update on that soon.

> Would supporting classes to NSDate like NSDateComponents NSDateFormatter etc also get value semantics? 
> 
> Thank you!
> 

NSDateComponents will, but I forgot to put it on the list! Thanks for noticing that. I will fix it.

NSDateFormatter will remain a class type, at least for now. Formatters are part of a public class hierarchy (inheriting from NSFormatter), so if we want to turn them into value types I think we’ll need some additional motivation to change their API surface in this way.

Thanks,
- Tony

> 
>> On Apr 22, 2016, at 10:18 AM, Tony Parker via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Dear swift-evolution denizens,
>> 
>> As you know from our announcement of Swift Open Source and our work on naming guidelines, one of our goals for Swift 3 is to “drop NS” for Foundation. We want to to make the cross-platform Foundation API that is available as part of swift-corelibs feel like it is not tied to just Darwin targets. We also want to reinforce the idea that new Foundation API must fit in with the language, standard library, and the rapidly evolving design patterns we see in the community.
>> 
>> You challenged us on one part of this plan: some Foundation API just doesn’t “feel Swifty”, and a large part of the reason why is that it often does not have the same value type behavior as other Swift types. We took this feedback seriously, and I would like to share with you the start of an important journey for some of the most commonly used APIs on all of our platforms: adopting value semantics for key Foundation types.
>> 
>> We have been working on this for some time now, and the set of diffs that result from this change is large. At this point, I am going to focus effort on an overview of the high level goals and not the individual API of each new type. In order to focus on delivering something up to our quality standards, we are intentionally leaving some class types as-is until a future proposal. If you don’t see your favorite class on the list — don’t despair. We are going to iterate on this over time. I see this as the start of the process.
>> 
>> One process note: we are still trying to figure out the best way to integrate changes to API that ship as part of the operating system (which includes Foundation) into the swift-evolution review process. Swift-evolution is normally focused on changes to functionality in the compiler or standard library. In general, I don’t expect all new Foundation API introduced in the Darwin/Objective-C framework to go through the open source process. However, as we’ve brought up this topic here before, I felt it was important to bring this particular change to the swift-evolution list.
>> 
>> As always I welcome your feedback.
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0069-swift-mutability-for-foundation.md <https://github.com/apple/swift-evolution/blob/master/proposals/0069-swift-mutability-for-foundation.md>
>> 
>> Thanks,
>> - Tony
>> 
>> 
>> 
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> 

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