"Grab The City" is a challenge that wants you to extract the name of the city in a given sentence which the name is wrapped in pair of square bracket

Grab The City

func grabCity(_ str: String) -> String {
//  let regex = try! NSRegularExpression(pattern: "(\\w+)(?!.*\\w)", options: [])
  let regex = try! NSRegularExpression(pattern: "(?<=\\[)(.+?)(?=\\])", options: [])
  let result = regex.matches(in: str, options: [], range: NSRange(location: 0, length: str.count)).last
  /*
  for match in result {
    for n in 0..<match.numberOfRanges {
      let range = match.range(at: n)
      let r = str.index(str.startIndex, offsetBy: range.location)..<str.index(str.startIndex, offsetBy: range.location+range.length)
//      print(#line, #file.components(separatedBy: "/").last!, str.substring(with: r))
      print(#line, #file.components(separatedBy: "/").last!, str[r])
    }
  }
  */
  return result.map{ String(str[str.index(str.startIndex, offsetBy: $0.range.location)..<str.index(str.startIndex, offsetBy: $0.range.location+$0.range.length)]) }!
//  return result.map{ String(str[Range($0.range, in: str)!]) }.joined()
}

print(#line, #file.components(separatedBy: "/").last!, grabCity("[Last Day!] Beer Festival [Munich]"))
print(#line, #file.components(separatedBy: "/").last!, grabCity("[50% Off!][Group Tours Included] 5-Day Trip to Onsen [Kyoto]"))
print(#line, #file.components(separatedBy: "/").last!, grabCity("[Duration: 7 hours] Tour of the Maritimes [Prince Edward Island]"))