[swift-evolution] [Review] SE-0005 Better Translation of Objective-C APIs Into Swift

[Matthew Johnson]

> On Feb 1, 2016, at 4:08 PM, Tony Parker <anthony.parker at apple.com> wrote:
> 
>> 
>> On Feb 1, 2016, at 1:49 PM, Matthew Johnson <matthew at anandabits.com <mailto:matthew at anandabits.com>> wrote:
>> 
>> 
>>> On Feb 1, 2016, at 3:38 PM, Drew Crawford via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> 
>>>> On Feb 1, 2016, at 1:02 PM, Tony Parker <anthony.parker at apple.com <mailto:anthony.parker at apple.com>> wrote:
>>>> 
>>>> Types like NSURL are intended to be the canonical URL for everyone to use,
>>> 
>>> 
>>> I think the "canonical URL for everyone to use" must be a value type / struct.  To me this seems axiomatic.
>>> 
>>> Meanwhile (NS)URL cannot be a value type because of the Darwin compatibility mandate, and to change from value->reference semantics would be "off the charts" breakage severity.
>>> 
>>> This is a requirements conflict.  corelibs-foundation can either be Darwin-compatible or it can be canonical, but we cannot do both.  Right now we have chosen Darwin-compatible, so we must let the canonical requirement go.   Unprefixed "URL" should be reserved for the value type that can actually work as a canonical API.
>> 
>> +1.  I was pretty shocked by that sentence as well.  The intention to canonize reference types just because they already exist could not be INVHO further from the right intention for Swift.  I understand and accept the short-term rationale for leveraging them.  I do not understand why we would settle for them as the long-term canonical solution.
>> 
> 
> Foundation is not a short term library. The reason we put it into Swift core libraries is because we intend for it to provide the most commonly needed functionality in one well-known, well-maintained place.

I applaud making the functionality available in a single source.  My objection is specifically focused on adopting reference types where value types make sense just because they already exist in Foundation.

> 
> Dropping the NS is one part of how we intend to make Foundation a great part of Swift. We are working on other ways as well.

I hope that transitioning to value types where that is the more Swifty design is a part of that plan if we’re going to stick with Foundation (which is fine as long as it doesn’t interfere with the desire for value types).

-Matthew

> 
> - Tony
> 
>>> 
>>> It's not clear to me if Foundation will actually be in a position to provide that API (e.g. in Swift 4, etc.) or whether some third party will provide a "URL" framework that gains traction first.  But in any case, we are not going to do it in the Swift 3 window, unless a lot of core scope decisions get re-decided.
>>> 
>>> 
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