[ios] Getting list of files in documents folder

Simple and dynamic solution (Swift 5):

extension FileManager {

  class func directoryUrl() -> URL? {
      let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
      return paths.first
  }

  class func allRecordedData() -> [URL]? {
     if let documentsUrl = FileManager.directoryUrl() {
        do {
            let directoryContents = try FileManager.default.contentsOfDirectory(at: documentsUrl, includingPropertiesForKeys: nil)
            return directoryContents.filter{ $0.pathExtension == "m4a" }
        } catch {
            return nil
        }
     }
     return nil
  }}