Removing value from UITableView causes crash - ios

Question

I have a UITableView and when I click on a cell I update a value in firebase to be true. I also implemented the ability to delete the UITableViewCell. The problem is that if the cell has been clicked on (updated) and then deleted the app crashes. When I have a look in firebase the value that has been updated has not been deleted (everything else has been), this only happens if the cell has been updated. This is what I got
// remove task
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
let taskToDelete = groupTask[indexPath.row]
if editingStyle == UITableViewCellEditingStyle.delete {
groupTask.remove(at: indexPath.row)
DataService.instance.REF_GROUPS.child(group!.key).child("task").child(taskToDelete.id).removeValue(completionBlock: { (error, refer) in
if error != nil {
} else {
}
})
self.tableView.reloadData()
}
}
// update task value
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let cell = tableView.cellForRow(at: indexPath) as? GroupTaskCell else { return }
if cell.isSelected == true {
let selected = groupTask[indexPath.row]
DataService.instance.REF_GROUPS.observe(.value) { (snapShot) in
DataService.instance.updateTaskStatus(desiredGroup: self.group!, selected: true, atIndexpath: indexPath.row, childPath: selected.id, handler: { (complete) in
self.tableView.reloadData()
})
}
} else {
}
self.tableView.reloadData()
}
// update task status
func updateTaskStatus(desiredGroup: Group, selected: Bool, atIndexpath: Int, childPath: String, handler: #escaping (_ taskArray: [Task]) -> ()) {
REF_GROUPS.child(desiredGroup.key).child("task").child(childPath).updateChildValues(["selected": selected])
}
EDIT!
Could not cast value of type 'NSNull' (0x1b5915f18) to 'NSString' (0x1b5921ad8).
2018-01-01 17:38:53.431901+0200 WireUp[587:103199] Could not cast value of type 'NSNull' (0x1b5915f18) to 'NSString' (0x1b5921ad8).
(lldb)
What firebase looks like before I delete the task:
And after:
As you can see it is not removing the value that has been updated and that is what's causing the crash. I appreciate all help.
func addTask(withTask task: String, andPeople people: String, forUID uid: String, withGroupKey groupKey: String?, selectedStatus selected: Bool, sendComplete: #escaping (_ taskCreated: Bool ) -> ()) {
if groupKey != nil {
REF_GROUPS.child(groupKey!).child("task").childByAutoId().updateChildValues(["taskToDo": task, "peopleToDoTask": people, "senderId": uid, "selected": selected])
sendComplete(true)
} else {
}
}
func updateTaskStatus(desiredGroup: Group, selected: Bool, childPath: String, handler: #escaping (_ taskArray: [Task]) -> ()) {
REF_GROUPS.child(desiredGroup.key).child("task").child(childPath).updateChildValues(["selected": selected])
}
func configureTaskCell(taskToDo task: String, nameForPerson name: String, isSelected: Bool ) {
self.task.text = task
self.name.text = name
if isSelected {
self.chechImg.isHidden = false
} else {
self.chechImg.isHidden = true
}
}

Answer 1

Instead of using self.tableView.reloadData() from within the table view delegate functions try updating and deleting cells using the beginUpdate() and endUpdate() methods of UITableView. You won't crash and you won't be reloading the whole table. In Obj-C, it looks like this for removing and updating a cell:
[tableView beginUpdates];
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView endUpdates];
[tableView beginUpdates];
[self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObjects: indexPath, nil] withRowAnimation:UITableViewRowAnimationNone];
[tableView endUpdates];

Answer 2

It seems as though the code you've provided isn't the issue. It's being deleted correctly but as you delete it, it's also updating again with just the selected: true. Somewhere in your code, it'll be trying to fetch the rest of the data, including the selected: true BUT it's not there; resulting in the crash. You may want to do some debugging to see where you're actually updating this selected value to your database and get rid of it