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
