类型“ NSLinguisticTag”的值没有成员“ range”

Question

I have text direction code its working good with swift 3 but after migration to swift 4, I got error

let tagScheme = [NSLinguisticTagScheme.language]
    let tagger    = NSLinguisticTagger(tagSchemes: tagScheme, options: 0)
    tagger.string = self.text
    let lang      = tagger.tag(at: 0, scheme: NSLinguisticTagScheme.language,
                                      tokenRange: nil, sentenceRange: nil)

    if lang?.range(of: "he") != nil ||  lang?.range(of: "ar") != nil { //Value of type 'NSLinguisticTag' has no member 'range' 
        self.textAlignment = NSTextAlignment.right
    } else {
        self.textAlignment = NSTextAlignment.left
    }

Anyone know how to fix this? thanks

Answer 1

As of Swift 4, NSLinguisticTagger returns tags not as (optional) strings, but as (optional) values of NSLinguisticTag :

public struct NSLinguisticTag : RawRepresentable, Equatable, Hashable {
    public init(_ rawValue: String)
    public init(rawValue: String)
}

You get the underlying string with the rawValue property:

 if let lang = tagger.tag(at: 0, scheme: .language, tokenRange: nil, sentenceRange: nil) {
    print(lang.rawValue)
    if lang.rawValue.hasPrefix("he") { ... }
}

If you want to check for equality and not for containment then you can also define your own NSLinguisticTag constants:

extension NSLinguisticTag {
    static let hebrew = NSLinguisticTag("he")
}

and use them as

if let lang = tagger.tag(at: 0, scheme: .language, tokenRange: nil, sentenceRange: nil) {
    if lang == .hebrew { ... }
}

Another option would be to define a custom computed property

extension NSLinguisticTag {
    var isRightToLeft: Bool {
        return rawValue.hasPrefix("he") || rawValue.hasPrefix("ar")
    }
}

and use it as

if let lang = tagger.tag(at: 0, scheme: .language, tokenRange: nil, sentenceRange: nil) {
    if lang.isRightToLeft { ... }
}