let localFileManager = FileManager()
let resourceKeys = Set<URLResourceKey>([.nameKey, .pathKey, .creationDateKey, .isDirectoryKey,.totalFileSizeKey])
let directoryEnumerator = localFileManager.enumerator(at: URL(string: "/")!, includingPropertiesForKeys: Array(resourceKeys), options: .skipsHiddenFiles)!
for case let fileURL as URL in directoryEnumerator {
            guard let resourceValues = try? fileURL.resourceValues(forKeys: resourceKeys),
                  let isDirectory = resourceValues.isDirectory,
                  let name = resourceValues.name,
                  let path = resourceValues.path,
                  let date = resourceValues.creationDate,
                  let size = resourceValues.totalFileSize
                else {
                    continue
            }
            if isDirectory {
                
                if name == "_extras" { // use this to exclude a given directory
                    directoryEnumerator.skipDescendants()
                }
            } else {
                
//                // append elements in date order here?
                
//                print(fileURL)
//                输出全部文件
//                print(resourceValues)
//
//                fileURLs.append(fileURL) // full URLs of files
//                fileNames.append(name) // file names only
//                filePaths.append(path) // paths of file
//                fileDates.append(date) // date and time that file was created
//
//                // sort arrays by creation date here?
                
            }
        }