UITableView and disappearing rows - ios

Question

I have an UITableView, quite standard, with quite dynamic datasource (messages).
To add messages to UITableView I'm using insertRows.
func insertRowsInTableAtIndexPath(ip: IndexPath, right: Bool) {
print("INSERT ROW visible cells: \(tableView.visibleCells.count)\n dispatcher messages \(dispatcher.messages.count)\n numberOfRows \(tableView.numberOfRows(inSection: 0))\n numberOfSections \(tableView.numberOfSections)\n ip: \(ip.row) \(ip.section)")
if tableView != nil {
if right == true {
self.tableView.insertRows(at: [ip], with: UITableView.RowAnimation.right)
} else {
self.tableView.insertRows(at: [ip], with: UITableView.RowAnimation.left)
}
}
print("AFTER INSERT ROW visible cells: \(tableView.visibleCells.count)\n dispatcher messages \(dispatcher.messages.count)\n numberOfRows \(tableView.numberOfRows(inSection: 0))\n numberOfSections \(tableView.numberOfSections)\n ip: \(ip.row) \(ip.section)")
}
It looks pretty standard, because it is. The problem is that in some rare cases (I can replay them but it'd be quite difficult to describe them here) I'm getting the famous NSInternalInconsistencyException: Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (2) must be equal to the number of rows contained in that section before the update (0) and so on.
In these cases the first message is successfully added to the dataSource, and it looks like this message also is inserted as row as well, but it doesn't show up on screen, and the next message is breaking my UITableView because it is invalide update (and it is).
I know that this is happening because of all of these print commands before and after inserting the cell. In bad case these numbers looks like that:
Before inserting the first message:
visible cells: 0
number of messages in dataSource: 1
numberOfRows: 0
numberOfSections: 1
ip: 0 0 (indexPath.row, indexPath.section)
After inserting the first message:
visible cells: 1
number of messages in dataSource: 1
numberOfRows: 1
numberOfSections: 1
ip: 0 0 (indexPath.row, indexPath.section)
At this point I can't see that cell (that was successfully inserted if I could believe UITableView.visibleCells.count)
But if I'm trying to insert the next message, I'm getting an exception. Moreover: UITableView.visibleCells.count is suddenly 0, and numberOfRows is 0 too, although I didn't remove previous row and I didn't remove this message from dataSource.
visible cells: 0
dispatcher messages 2
numberOfRows 0
numberOfSections 1
ip: 0 0
So, I have three questions:
Is it possible for UITableView to not to insert row with insertRows, and how could I prevent this behavior. Why the first row is not showing in the first place?
Why this first row is disappearing from numberOfRows and visibleCells after a while?
What am I doing wrong here?
I understand that this amount of code is not enough to solve this issue from scratch, but this UITableView is pretty standard, and dataSource logic is not so standard and relatively complicated, so my only hope is for people who already have experienced something like that.
update (dataSource methods):
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return dispatcher.messages.count
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
update 2 (the most relevant part of the code):
//this should work when user is changing from one 'chat' to another
//so, first of all, I'm removing all the messages from the dataSource
dispatcher.messages.removeAll()
//also, I'm stopping the timer
if timer != nil {
timer.invalidate()
timer = nil
}
//also, I'm reloading the table with no messages
if tableView != nil {
tableView.reloadData()
}
//after that I'm starting the timer again, and trying to add new messages to the UITableView. The first message is going through (although it is not shown in the UITableView as it should be), the second message is throwing an error because the first row doesn't exist at this point).
let newMessage = dispatcher.giveMeNewMessage()
if newMessage != nil {
dispatcher.messages.insert(newMessage!, at: 0)
let ip = IndexPath(row: 0, section: 0)
insertRowsInTableAtIndexPath(ip: ip, right: false)
self.scrollToRow(ip: ip) //standard scrollToRow
}