Обработчик запроса не найден:

Swift 4

extension String {

    func slice(from: String, to: String) -> String? {

        return (range(of: from)?.upperBound).flatMap { substringFrom in
            (range(of: to, range: substringFrom..<endIndex)?.lowerBound).map { substringTo in
                String(self[substringFrom..<substringTo])
            }
        }
    }
}

Swift 3

extension String {

    func slice(from: String, to: String) -> String? {

        return (range(of: from)?.upperBound).flatMap { substringFrom in
            (range(of: to, range: substringFrom..<endIndex)?.lowerBound).map { substringTo in
                substring(with: substringFrom..<substringTo)
            }
        }
    }
}

Старый ответ:

import Foundation

extension String {
  func sliceFrom(start: String, to: String) -> String? {
    return (rangeOfString(start)?.endIndex).flatMap { sInd in
      (rangeOfString(to, range: sInd..<endIndex)?.startIndex).map { eInd in
        substringWithRange(sInd..<eInd)
      }
    }
  }
}

"javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"
  .sliceFrom("'", to: "',")