<div>This seems like a bug (missing feature?) in how the API is imported for Swift. You might consider filing a Radar.</div><div> <br><div class="gmail_quote"><div>On Thu, Feb 9, 2017 at 3:12 PM Michel Fortin via swift-users <<a href="mailto:swift-users@swift.org">swift-users@swift.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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.<br class="gmail_msg">
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Here's the documentation for that method:<br class="gmail_msg">
<a href="https://developer.apple.com/reference/foundation/nsattributedstring/1412616-string" rel="noreferrer" class="gmail_msg" target="_blank">https://developer.apple.com/reference/foundation/nsattributedstring/1412616-string</a><br class="gmail_msg">
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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:<br class="gmail_msg">
> 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.<br class="gmail_msg">
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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.<br class="gmail_msg">
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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.<br class="gmail_msg">
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--<br class="gmail_msg">
Michel Fortin<br class="gmail_msg">
<a href="https://michelf.ca" rel="noreferrer" class="gmail_msg" target="_blank">https://michelf.ca</a><br class="gmail_msg">
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