Swift.String で regex を用いた置換を行う

• 今は NSRegularExpression を使わないで Swift Regex を使うことも可能。

半角カナ → 全角カナ

extension String {
    /// 半角カナを全角カナに変換
    func replacingHalfKatakanaToFull() -> String {
        // regex: https://en.wikipedia.org/wiki/Halfwidth_and_Fullwidth_Forms_(Unicode_block)
        guard let regex = try? NSRegularExpression(pattern: "[ｦ-ﾟ]+") else { return self }
        var result = self
        let matched = regex.matches(in: self, range: NSRange(location: 0, length: utf16.count))
        matched.forEach {
            let substring = (result as NSString).substring(with: $0.range)
            let transformed = substring.applyingTransform(.fullwidthToHalfwidth, reverse: true)
            result = result.replacingOccurrences(of: substring, with: transformed ?? substring)
            print(result)
        }
        return result
    }
}

全角英数 → 半角英数

extension String {
    /// 全角英数字を半角英数字に変換
    func replacingFullAlphanumericToHalf() -> String {
        guard let regex = try? NSRegularExpression(pattern: "[０-９ａ-ｚＡ-Ｚ]+") else { return self }
        var result = self
        let matched = regex.matches(in: self, range: NSRange(location: 0, length: utf16.count))
        matched.forEach {
            let substring = (result as NSString).substring(with: $0.range)
            let transformed = substring.applyingTransform(.fullwidthToHalfwidth, reverse: false)
            result = result.replacingOccurrences(of: substring, with: transformed ?? substring)
            print(result)
        }
        return result
    }
}

Swift Regex