[swift-users] So how do you implement a NSTextStorage subclass in Swift?

[Jacob Bandes-Storch]

Got some clarity on this from Apple folks on Twitter:
https://twitter.com/jtbandes/status/830159670559993856

On Fri, Feb 10, 2017 at 12:54 PM, Michel Fortin <michel.fortin at michelf.ca>
wrote:

> I did file one (30314719). I might not have explained the problem clearly
> enough, I suppose, because at the time I was misinterpreting the API
> contract thinking it was the new AppKit Touch Bar stuff that was violating
> it instead. That bug now sits closed and I hesitate opening a new bug for
> the same problem just to ask it to be fixed in another way. Meanwhile I
> found an acceptable workaround that I attached to the existing bug report
> in addition and I posted all this to the list. Hopefully someone at the
> right place will notice.
>
> But yeah... maybe I should file another bug, against Foundation's Swift
> interface this time, since NSTextStorage's string property comes from
> NSAttributedString. I'll think about it.
>
>
> Le 10 févr. 2017 à 11:36, Jacob Bandes-Storch <jtbandes at gmail.com> a
> écrit :
>
> This seems like a bug (missing feature?) in how the API is imported for
> Swift. You might consider filing a Radar.
>
> On Thu, Feb 9, 2017 at 3:12 PM Michel Fortin via swift-users <
> swift-users at swift.org> wrote:
>
>> The `string` property of `NSTextStorage` is of type `String`, but the
>> contract it must implement is that it should return the backing store of
>> the attributed string (the underlying `NSMutableString` used as the backing
>> store). It seems to me that this makes it impossible to implement correctly
>> a subclass of `NSTextStorage` in Swift, because Swift automatically wraps
>> the `NSString` into a `String` and the underlying mutable storage is not
>> passed around.
>>
>> Here's the documentation for that method:
>> https://developer.apple.com/reference/foundation/
>> nsattributedstring/1412616-string
>>
>> In case the contract isn't clear from the documentation (it wasn't for
>> me), I got a confirmation as a response in radar 30314719:
>> > It’s returning a copy of the backing store, but the contract is
>> actually returning the backing store string. The copy storage declaration
>> in the property spec is only used for setter implementation.
>>
>> So looks like this is impossible to model correctly in Swift due to the
>> automatic bridging to `String`. Some APIs in AppKit expect the `NSString`
>> they receive to mutate when mutating the text storage (touch bar
>> suggestions in `NSTextView`) and will do bad things this isn't the case.
>>
>> Obviously, I can work around this by writing some Objective-C code, but
>> it'd be better if I could avoid splitting the class implementation between
>> two languages. There's another way using swizzling to map the Objective-C
>> method to a Swift implementation of the same method that has the correct
>> signature, and that's probably what I'll end up doing unless a better
>> solution can be pointed out to me.
>>
>>
>> --
>> Michel Fortin
>> https://michelf.ca
>>
>> _______________________________________________
>> swift-users mailing list
>> swift-users at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
>>
>
> --
> Michel Fortin
> https://michelf.ca
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170210/7edf8c71/attachment.html>