[swift-corelibs-dev] Bring NSString functions to String

Andrey Fidrya af at zabiyaka.com
Wed May 10 06:19:02 CDT 2017

Hi All,

Btw, when migrating from NSString's methods to URL I've noticed
that they work a bit differently: URL's methods convert strings
from NFC to NFD (decomposed) unicode form which is demonstrated
by the example below.

I had to additionally call .precomposedStringWithCanonicalMapping
on resulting string to convert it back to NFC form.

This was very surprising as it wasn't mentioned anywhere in docs
and has broken non-english filename support in app.
Is this expected behavior or a bug?

//let source = "/my_file.txt"
let source = "/мой_файл.txt" // problematic is letter 'й'

let disallowedCharacters = CharacterSet(charactersIn: source).inverted

do {
    print("--- NSString:")
    let result = (source as NSString).deletingPathExtension as String
    print(result.rangeOfCharacter(from: disallowedCharacters))


do {
    print("--- String + URL:")
    let result = URL(fileURLWithPath: source).deletingPathExtension().path
    print(result.rangeOfCharacter(from: disallowedCharacters))
    print(result.precomposedStringWithCanonicalMapping.rangeOfCharacter(from: disallowedCharacters))

--- Output:

--- NSString:
--- String + URL:
Optional(Range(Swift.String.CharacterView.Index(_base: Swift.String.UnicodeScalarView.Index(_position: 3), _countUTF16: 2)..<Swift.String.CharacterView.Index(_base: Swift.String.UnicodeScalarView.Index(_position: 4), _countUTF16: 1)))


> On 10 May 2017, at 12:45, Eric Blachère via swift-corelibs-dev <swift-corelibs-dev at swift.org> wrote:
> Thanks for the answer ! It seems a bit weird from them to advocate using NSString methods in the unavailability comment. I would rather use URL when I can even if the conversions are a bit tedious ^^
> Thanks a lot,
> Eric
> 2017-05-10 10:52 GMT+02:00 Brent Royal-Gordon <brent at architechies.com <mailto:brent at architechies.com>>:
> > On May 8, 2017, at 9:39 AM, Eric Blachère via swift-corelibs-dev <swift-corelibs-dev at swift.org <mailto:swift-corelibs-dev at swift.org>> wrote:
> >
> > I was just wondering if there are plans to bring NSString functions manipulating paths into the native String class. (such as lastPathComponent, pathComponents etc...)
> > Because even if we can always make an extension of String to easily cast it into NSString, it's still a bit of a shame to have to do it ;)
> Unfortunately, it seems like the decision not to include these methods on String was quite deliberate.
> Here's the revision where that happened: <https://github.com/apple/swift/commit/1f2390f1c75be65f57f189247bfe4f9b2fc11e3b#diff-d38f60064c3752f096c043e756d8f201R925 <https://github.com/apple/swift/commit/1f2390f1c75be65f57f189247bfe4f9b2fc11e3b#diff-d38f60064c3752f096c043e756d8f201R925>> As you can see, they had that working and chose to disable it, presumably because they want you to manipulate paths through `URL`. (I wish the radar referenced in the commit message were public, but alas, it's not.)
> --
> Brent Royal-Gordon
> Architechies
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> swift-corelibs-dev at swift.org
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