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@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@swift.org > https://lists.swift.org/mailman/listinfo/swift-users >
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