Reload tableView data from UIAlertController not working - ios

Question

I'm having trouble refreshing tableView data from a UIAlertController.
The code is for a quiz-style app and this page lets the user choose
subjects as well as some other options (see screenshots). There is a
reset button next to "Show only unseen questions" which triggers a
UIAlertController. However, clicking the Reset action in this alert
updates the database but doesn't update the tableView. The database is
definitely updated as if I go back a page and then revisit the
tableView, the unseen question values in the subject cells are updated. I realise there's quite a few of
these type of questions here but I'm afraid none of the usual fixes are
working.
Extra info:
The tableView is customised with a series of custom
UITableViewCells
Data is loaded from a SQLite database through FMDB
The UIAlertController is triggered from a NSNotification when the reset
button is clicked
So far I have:
Checked datasource and delegates set correctly, programmatically and
in IB. Confirmed with print(self.tableView.datasource) etc
Confirmed reloadData() is firing
Using main thread for reloadData()
Extract of TableViewController code and screenshots below.
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.dataSource = self
self.tableView.delegate = self
//For unique question picker changed
NotificationCenter.default.addObserver(self, selector: #selector(SubjectsTableViewController.reloadView(_:)), name:NSNotification.Name(rawValue: "reload"), object: nil)
//For slider value changed
NotificationCenter.default.addObserver(self, selector: #selector(SubjectsTableViewController.updateQuantity(_:)), name:NSNotification.Name(rawValue: "updateQuantity"), object: nil)
//Trigger UIAlertController
NotificationCenter.default.addObserver(self, selector: #selector(SubjectsTableViewController.showAlert(_:)), name:NSNotification.Name(rawValue: "showAlert"), object: nil)
}
// MARK: - Table view data source
///////// Sections and Headers /////////
override func numberOfSections(in tableView: UITableView) -> Int {
return 3
}
override func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView?
{
let subjectHeaderCell = tableView.dequeueReusableCell(withIdentifier: "sectionHeader")
switch section {
case 0:
subjectHeaderCell?.textLabel?.text = "Select Subjects"
return subjectHeaderCell
case 1:
subjectHeaderCell?.textLabel?.text = "Options"
return subjectHeaderCell
case 2:
subjectHeaderCell?.textLabel?.text = ""
return subjectHeaderCell
default:
subjectHeaderCell?.textLabel?.text = ""
return subjectHeaderCell
}
}
//Header heights
override func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat
{
return 34.0
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case 0:
return SubjectManager.subjectWorker.countSubjects()
case 1:
return 2
case 2:
return 1
default:
return 0
}
}
///////// Rows within sections /////////
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
switch (indexPath.section) {
case 0:
//Configure subjectCell //
let cellWithSubject = tableView.dequeueReusableCell(withIdentifier: "subjectCell", for: indexPath) as! SubjectTableViewCell
//Curve corners
cellWithSubject.subjectCellContainer.layer.cornerRadius = 2
cellWithSubject.subjectCellContainer.layer.masksToBounds = true
//Set subject title label
cellWithSubject.subjectTitleLabel.text = SubjectManager.subjectWorker.collateSubjectTitles()[indexPath.row]
//Available questions for subject label
questionCountForSubjectArray = QuestionManager.questionWorker.countQuestions()
cellWithSubject.subjectAvailableQuestionsLabel.text = "Total questions available: \(questionCountForSubjectArray[indexPath.row])"
//Get questions in subject variables
seenQuestionsForSubjectArray = QuestionManager.questionWorker.countOfQuestionsAlreadySeen()
//New questions available label
unseenQuestionsForSubjectArray.append(questionCountForSubjectArray[indexPath.row] - seenQuestionsForSubjectArray[indexPath.row])
cellWithSubject.newQuestionsRemainingLabel.text = "New questions remaining: \(unseenQuestionsForSubjectArray[indexPath.row])"
return cellWithSubject
case 1:
switch (indexPath.row) {
case 0:
//Configure uniqueQuestionCell //
let cellWithSwitch = tableView.dequeueReusableCell(withIdentifier: "uniqueQuestionCell", for: indexPath) as! UniqueQuestionTableViewCell
//Curve corners
cellWithSwitch.uniqueQuestionContainer.layer.cornerRadius = 2
cellWithSwitch.uniqueQuestionContainer.layer.masksToBounds = true
return cellWithSwitch
case 1:
//Configure sliderCell //
let cellWithSlider = tableView.dequeueReusableCell(withIdentifier: "questionPickerCell", for: indexPath) as! QuestionPickerTableViewCell
//Curve corners
cellWithSlider.pickerCellContainer.layer.cornerRadius = 2
cellWithSlider.pickerCellContainer.layer.masksToBounds = true
//Set questions available label
cellWithSlider.questionsAvailableLabel.text = "Available: \(sumQuestionsSelected)"
//Configure slider
cellWithSlider.questionPicker.maximumValue = Float(sumQuestionsSelected)
cellWithSlider.questionPicker.isContinuous = true
//Logic for if available questions changes - updates slider stuff
if questionQuantityFromSlider > sumQuestionsSelected {
questionQuantityFromSlider = sumQuestionsSelected
cellWithSlider.questionsToStudy = questionQuantityFromSlider
cellWithSlider.questionsChosenLabel.text = "Questions to study: \(questionQuantityFromSlider)"
} else { questionQuantityFromSlider = cellWithSlider.questionsToStudy
}
//Configure questions chosen label:
if questionsToStudyDict.isEmpty {
cellWithSlider.chooseSubjectsLabel.text = "Choose a subject"
cellWithSlider.questionsChosenLabel.text = "Questions to study: 0"
} else {
cellWithSlider.chooseSubjectsLabel.text = ""
}
return cellWithSlider
default:
return UITableViewCell()
}
case 2:
print("cellForRowAt case 2")
//Configure beginCell //
let cellWithStart = tableView.dequeueReusableCell(withIdentifier: "beginCell", for: indexPath) as! BeginStudyTableViewCell
//Curve corners
cellWithStart.startContainer.layer.cornerRadius = 2
cellWithStart.startContainer.layer.masksToBounds = true
return cellWithStart
default:
return UITableViewCell()
}
}
//Row heights
override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
switch (indexPath.section) {
case 0:
return 120.0
case 1:
switch (indexPath.row) {
case 0:
return 60.0
case 1:
return 100.0
default:
return 44.0
}
case 2:
return 100.0
default:
return 44.0
}
}
override func tableView(_ tableView: UITableView, shouldHighlightRowAt indexPath: IndexPath) -> Bool {
if indexPath.section == 2 || indexPath.section == 0 {
return true
} else {
return false
}
}
override func tableView(_ tableView: UITableView, didHighlightRowAt indexPath: IndexPath) {
if indexPath.section == 2 && selectedRowsDict.isEmpty != true && questionQuantityFromSlider > 0 {
let cellToBegin = tableView.cellForRow(at: indexPath) as! BeginStudyTableViewCell
cellToBegin.startContainer.backgroundColor = UIColor.lightGray
}
}
override func tableView(_ tableView: UITableView, didUnhighlightRowAt indexPath: IndexPath) {
if indexPath.section == 2 {
let cellToBegin = tableView.cellForRow(at: indexPath) as! BeginStudyTableViewCell
cellToBegin.startContainer.backgroundColor = UIColor.white
}
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
switch (indexPath.section) {
case 0:
//Set checkbox to ticked image
let cellWithSubject = tableView.cellForRow(at: indexPath) as! SubjectTableViewCell
cellWithSubject.subjectSelectedImageView.image = UIImage(named: "CheckboxTicked")
//Determine questions available for subject depending on unseen value
if showUnseenQuestions == true {
questionsToStudyDict[indexPath.row] = unseenQuestionsForSubjectArray[indexPath.row]
} else {
questionsToStudyDict[indexPath.row] = questionCountForSubjectArray[indexPath.row]
}
//Sum questions available
sumQuestionsSelected = Array(questionsToStudyDict.values).reduce(0, +)
//Reload table to pass this to questions available label in UISlider cell and reselect selected rows
let key: Int = indexPath.row
selectedRowsDict[key] = indexPath.row
self.tableView.reloadData()
if selectedRowsDict.isEmpty == false {
for (keys,_) in selectedRowsDict {
let index: IndexPath = NSIndexPath(row: selectedRowsDict[keys]!, section: 0) as IndexPath
tableView.selectRow(at: index, animated: false, scrollPosition: .none)
}
}
case 1:
break
case 2:
if selectedRowsDict.isEmpty != true && questionQuantityFromSlider > 0 {
self.performSegue(withIdentifier: "showStudyQuestion", sender: self)
} else {
print("Segue not fired")
}
default:
break
}
}
override func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
if indexPath.section == 0 {
//Set checkbox to unticked image
let cellWithSubject = tableView.cellForRow(at: indexPath) as! SubjectTableViewCell
cellWithSubject.subjectSelectedImageView.image = UIImage(named: "Checkbox")
//Remove questions available for unselected subject from questions dictionary
questionsToStudyDict[indexPath.row] = nil
//Update sum of questions selected
sumQuestionsSelected = Array(questionsToStudyDict.values).reduce(0, +)
//Reload table to pass this to questions available label in UISlider cell and reselect selected rows
let key: Int = indexPath.row
selectedRowsDict[key] = nil
self.tableView.reloadData()
if selectedRowsDict.isEmpty == false {
for (keys,_) in selectedRowsDict {
let index: IndexPath = NSIndexPath(row: selectedRowsDict[keys]!, section: 0) as IndexPath
tableView.selectRow(at: index, animated: false, scrollPosition: .none)
}
}
}
}
func reloadView(_ notification: Notification) {
//Change bool value
showUnseenQuestions = !showUnseenQuestions
//For keys in dict, update values according to showUnseenQuestion value
if showUnseenQuestions == true {
for (key,_) in questionsToStudyDict {
questionsToStudyDict[key] = unseenQuestionsForSubjectArray[key]
}
} else {
for (key,_) in questionsToStudyDict {
questionsToStudyDict[key] = questionCountForSubjectArray[key]
}
}
//Re-run sum dict function
sumQuestionsSelected = Array(questionsToStudyDict.values).reduce(0, +)
//Finally reload the view and reselect selected rows
let selectedRowsIndexes = tableView.indexPathsForSelectedRows
self.tableView.reloadData()
if selectedRowsIndexes != nil {
for i in (selectedRowsIndexes)! {
tableView.selectRow(at: i, animated: false, scrollPosition: .none)
}
}
}
func updateQuantity(_ notification: Notification) {
//Reload the view and reselect selected rows
let selectedRowsIndexes = tableView.indexPathsForSelectedRows
self.tableView.reloadData()
if selectedRowsIndexes != nil {
for i in (selectedRowsIndexes)! {
tableView.selectRow(at: i, animated: false, scrollPosition: .none)
}
}
}
func showAlert(_ notification: Notification) {
let alertController = UIAlertController(title: "Reset Seen Questions", message: "Are you sure you want to reset all questions to unseen?", preferredStyle: .alert)
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { action in
// ...
}
alertController.addAction(cancelAction)
let OKAction = UIAlertAction(title: "Reset", style: .default, handler:{(action:UIAlertAction) -> Void in
QuestionManager.questionWorker.resetHasSeenValues()
self.reloadData()
print("reloadData fired")
})
alertController.addAction(OKAction)
self.present(alertController, animated: true, completion: nil)
}
func reloadData() {
DispatchQueue.main.async(execute: {
self.tableView.reloadData()
})
}
func countOfQuestionsAlreadySeen() -> [Int] {
var questionSeenYesArray: [Int] = []
if openWriteDatabase() {
let queryYes = "SELECT SUM(hasSeen) FROM UserData GROUP BY subjectID"
let querySeenYes: FMResultSet? = writeDatabase?.executeQuery(queryYes, withArgumentsIn: nil)
while (querySeenYes?.next())! {
if let questionSeenYes = (querySeenYes?.int(forColumnIndex: 0)) {
questionSeenYesArray.append(Int(questionSeenYes))
}
}
}
return questionSeenYesArray
}
func resetHasSeenValues() {
if openWriteDatabase() {
let resetHasSeenValues = "UPDATE UserData Set hasSeen = 0"
_ = writeDatabase?.executeUpdate(resetHasSeenValues, withArgumentsIn: nil)
}
}

Answer 1

Some more debugging revealed that the unseenQuestionsForSubjectArray wasn't being populated correctly in the cellForRowAt method. I fixed this, and this fixed the reloadData() issue. Thanks all for the help.

Answer 2

add self.reloadData() inside main queue. Outlet changes always should be held inside main thread.
let OKAction = UIAlertAction(title: "Reset", style: .default, handler:{(action:UIAlertAction) -> Void in
QuestionManager.questionWorker.resetHasSeenValues()
DispatchQueue.main.async {
self.tableView.reloadData()
}
print("reloadData fired")
})