Extension function for Swift Strings that will accept a NSMutableArray argument

Swift - StringWithFormat.swift

  static func withFormat(format: String, list:NSMutableArray) -> String {
    if list.count > 0 {
      let path = String(format: format, list.firstObject as! String)
      list.removeObject(list.firstObject!)
      return self.withFormat(path, list: list)
    } else {
      return format
    }
  }