struct Response: Decodable {
  let events: [MeetingEvent]
}

let json = """
{"events":[{"type":"user-joined","eventId":"0","userId":"1","timestamp":1562458678387,"userDisplayName":"321"},{"type":"user-joined","eventId":"1","userId":"2","timestamp":1562458678387,"userDisplayName":"1233"},{"type":"hand-up","eventId":"2","userId":"1","timestamp":1562458678387},{"type":"poll-created","eventId":"3","userId":"1","timestamp":0,"pollId":"1"},{"type":"poll-voted","eventId":"4","userId":"2","timestamp":0,"pollId":"1","thumbs":"down"},{"type":"poll-closed","eventId":"5","userId":"1","timestamp":0,"pollId":"1","results":{"thumbsUp":0,"thumbsDown":1}},{"type":"hand-up","eventId":"6","userId":"2","timestamp":1562458678387},{"type":"hand-down","eventId":"7","userId":"1","timestamp":1562458678387},{"type":"poll-created","eventId":"8","userId":"2","timestamp":0,"pollId":"2"},{"type":"poll-voted","eventId":"9","userId":"1","timestamp":0,"pollId":"2","thumbs":"down"},{"type":"poll-closed","eventId":"10","userId":"2","timestamp":0,"pollId":"2","results":{"thumbsUp":0,"thumbsDown":1}},{"type":"user-left","eventId":"11","userId":"1","timestamp":1562458678387},{"type":"user-joined","eventId":"12","userId":"3","timestamp":1562458678387,"userDisplayName":"321"},{"type":"hand-up","eventId":"13","userId":"3","timestamp":1562458678387}]}
"""

if let data = json.data(using: .utf8) {
  let response = try JSONDecoder().decode(Response.self, from: data)
  response.events.forEach { event in
    switch event.event {
    case let joined as JoinedEvent:
      print("Joined Event: \(joined.userDisplayName)")
    case let voted as PollVotedEvent:
      print("Voted Event: \(voted.thumbs)")
    default:
      print("Other event")
    }
  }
}