LanguageDetector.swift

//
//  LanguageDetector(Swift3.x).swift
//  Musubi
//
//  Created by はるふ on 2017/07/12.
//  Copyright ©ha1f 2017年 line. All rights reserved.
//

import Foundation

struct LanguageDetector {
    
    static let notDetermined = "und"
    
    private let tagger = NSLinguisticTagger(tagSchemes: [NSLinguisticTagSchemeLanguage], options: 0)
    
    // returns BCP-47 format
    func detect(_ text: String) -> String {
        guard !text.isEmpty else {
            return LanguageDetector.notDetermined
        }
        tagger.string = text
        return tagger.tag(at: 0, scheme: NSLinguisticTagSchemeLanguage, tokenRange: nil, sentenceRange: nil) ?? LanguageDetector.notDetermined
    }
}

//
//  LanguageDetector(Swift4.x).swift
//  Musubi
//
//  Created by はるふ on 2017/07/12.
//  Copyright ©ha1f 2017年 line. All rights reserved.
//

import Foundation

public struct LanguageDetector {
    
    static let undetermined = "und"
    
    private let tagger = NSLinguisticTagger(tagSchemes: [.language], options: 0)
    
    // returns BCP-47 format
    func detect(_ text: String) -> String {
        guard !text.isEmpty else {
            return LanguageDetector.undetermined
        }
        tagger.string = text
        return tagger.tag(at: 0, scheme: .language, tokenRange: nil, sentenceRange: nil) ?? LanguageDetector.undetermined
    }
}

//
//  LanguageDetectorTests.swift
//  MusubiTests
//
//  Created by はるふ on 2017/07/12.
//  Copyright ©ha1f 2017年 line. All rights reserved.
//

import XCTest
@testable import Musubi

class LanguageDetectorTests: XCTestCase {
    
    let detector = LanguageDetector()
    
    func testDetect() {
        let de = "Rom ist nicht an einem Tag erbaut worden"
        let ja = "ローマは一日にして成らず"
        let fr = "Paris ne s'est pas fait en un jour"
        let en = "Rome was not built in a day"
        let it = "Roma non fu fatta in un giorno, Roma non è stata costruita in un giorno"
        let el = "Η Ρώμη δεν χτίστηκε σε μια μέρα"
        let ru = "Москва не сразу строилась"
        let zh_Hant = "羅馬非朝夕建成的"
        let zh_Hans = "罗马不是一日建成的"
        let ko = "로마는 하루아치메 이루어지지 아낟따"
        let th = "และจะมีคุณค่า'มากขึ้น'เมื่อเราทำความดีนั้นอย่างสม่ำเสมอ"
        
        XCTAssertEqual(detector.detect(de), "de")
        XCTAssertEqual(detector.detect(ja), "ja")
        XCTAssertEqual(detector.detect(en), "en")
        XCTAssertEqual(detector.detect(fr), "fr")
        XCTAssertEqual(detector.detect(it), "it")
        XCTAssertEqual(detector.detect(el), "el")
        XCTAssertEqual(detector.detect(ru), "ru")
        XCTAssertEqual(detector.detect(zh_Hant), "zh-Hant")
        XCTAssertEqual(detector.detect(zh_Hans), "zh-Hans")
        XCTAssertEqual(detector.detect(ko), "ko")
        XCTAssertEqual(detector.detect(th), "th")
    }
    
    func testDetectUnd() {
        XCTAssertEqual(detector.detect(""), LanguageDetector.notDetermined)
        XCTAssertEqual(detector.detect("a"), LanguageDetector.notDetermined)
        XCTAssertEqual(detector.detect("大"), LanguageDetector.notDetermined)
    }
}

http://qiita.com/_ha1f/items/3f45ed483e8366fbe81c