ios - Get Error "Index out of range" When I frequently push/back viewcontroller in real device - Swift -

i have problem tableview.
when push/back between chatlistviewcontroller , detailviewcontroller, crash , error in listviewcontroller.
don't know data make crash.
guess whether use gcd make happen or not?
have advice avoid it?
thanks.

crash log:
fatal error: index out of range

model:

class chatroomlist:model {      var all:[chatroom] {     var rooms:[chatroom] = [chatroom]()     self.chatrooms.foreach({ (id,chatroom) in         if showtype.contains(chatroom.type) {             rooms.append(chatroom)         }     })     return rooms     } } 

viewcontroller:

import rxcocoa import rxswift import alamofire  class listviewcontroller: uiviewcontroller, uitableviewdatasource, uitableviewdelegate {                           let chatrooms:chatroomlist = chatroomlist()     var list:[chatroom] = [chatroom]()     var subscribe:disposable?      override func viewdidload() {     super.viewdidload()      self.tableview.datasource = self     self.tableview.delegate = self      }      override func viewwillappear(_ animated: bool) {         super.viewwillappear(animated)          subscribe = rooms.notifysubject.subscribe({ json in                 self.loadcontents()         })         self.loadcontents()     }      override func viewwilldisappear(_ animated: bool) {         super.viewwilldisappear(animated)          subscribe?.dispose()     }      func loadcontents() {          var idlist:[string] = []          self.list.removeall()         self.list = chatrooms.all          guard self.list.isempty == false else {             return         }          dispatchqueue.global().async() {              self.list = self.list.filter { (chatroom) -> bool in                 if chatroom.id.isempty {                     return true                 }                 if idlist.contains(chatroom.id) {                     return false                 }                 idlist.append(chatroom.id)                 return true             }                 self.list.sort(by: { (a,b) in                 if a.message.datetime.isempty {                     return false                 }              return a.message.datetime > b.message.datetime         })          dispatchqueue.main.async() {              self.tableview.reloaddata()         }       }     } } func tableview(_ tableview: uitableview, numberofrowsinsection section: int) -> int {     return list.count }     func tableview(_ tableview: uitableview, cellforrowat indexpath: indexpath) -> uitableviewcell {      if list[indexpath.row].type == .city {          let cell: chatroomcitytableviewcell = chatroomcitytableviewcell(style: .default, reuseidentifier: nil)          cell.loadbycitychatroom(chatroom: list[indexpath.row], cityid: list[indexpath.row].cityid)          return cell     }else{          let cell: chatroomtableviewcell = chatroomtableviewcell(style: .default, reuseidentifier: nil)         cell.loadbychatroom(chatroom: list[indexpath.row])          return cell     } } 

enable zombie objects in scheme.

select application scheme -> run -> diagnostics -> check zombie objects.

run app now. give more precise information crash.

hope helps :)