FSCalendar's event dot does not appear

Question

FSCalendar's event dot does not appear. until I swipe to the next or previous month, the event dot doesn't show up. I do use calendar.reloadData() here is my code:

 func calendar(_ calendar: FSCalendar, numberOfEventsFor date: Date) -> Int {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy/MM/dd"
    dateFormatter.locale = Locale.init(identifier: "fa_IR")

    for dateStr in dates{
        if(dateFormatter.string(from: date) == dateStr)
        {
            return 1
            self.calendar.reloadData()
        }
    }
    return 0
}

I am also using calendar.reloadData() in viewDidLoad():

    super.viewDidLoad()

    self.calendar.firstWeekday = 7

    self.calendar.locale = Locale(identifier: "fa_IR")

    self.calendar.select(Date())
    self.calendar.identifier = NSCalendar.Identifier.persian.rawValue
    self.calendar.reloadData()

so what am i doing wrong?
I also tried putting my logic in will displaycell but that didn't work either. here is the whole view controller:

@IBOutlet weak var calendar: FSCalendar!

@IBAction func addEventButton(_ sender: UIBarButtonItem) {
    let date = Date()
    let formatter = DateFormatter()

    // initially set the format based on your datepicker date
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

    let myString = formatter.string(from: date)
    // convert your string to date
    let yourDate = formatter.date(from: myString)
    //then again set the date format whhich type of output you need

    formatter.calendar = Calendar (identifier: .persian)
    formatter.dateFormat = "yyyy/MM/dd"
    formatter.locale = Locale.init(identifier: "fa_IR")
    // again convert your date to string
    dateString = formatter.string(from: yourDate!)                

    self.performSegue(withIdentifier: "addEvent", sender: UIView.self)
}

  @IBOutlet weak var tblCalendar: UITableView!


func calendar(_ calendar: FSCalendar!, didSelectDate date: Date!) {

    eventIndex.removeAll()
    let formatter = DateFormatter()
    // initially set the format based on your datepicker date
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

    let myString = formatter.string(from: date)
    // convert your string to date
    let yourDate = formatter.date(from: myString)
    //then again set the date format whhich type of output you need

    formatter.calendar = Calendar (identifier: .persian)
    formatter.dateFormat = "yyyy/MM/dd"
    formatter.locale = Locale.init(identifier: "fa_IR")
    // again convert your date to string
    let selectedDate = formatter.string(from: yourDate!)

    var index = [Int()]
    if dates.isEmpty == false{
    for i in 0...dates.count - 1 {
        if dates[i] == selectedDate{
            index.append(i)
        }
        }
    }
        index.remove(at: 0)
    if index.isEmpty == false {
        for i in 0...index.count - 1 {
            let isIndexValid = dates.indices.contains(index[i])

            if  isIndexValid == true {
                let isEventValid = event.indices.contains(index[i])
                if isEventValid == true{
            eventIndex.append(event[index[i]])
                }
            }
    }
    }

    tblCalendar.reloadData()       
}

func calendar(_ calendar: FSCalendar, numberOfEventsFor date: Date) -> Int {
           return 0
}

func calendar(_ calendar: FSCalendar, willDisplay cell: FSCalendarCell, for date: Date, at position: FSCalendarMonthPosition){

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy/MM/dd"
    dateFormatter.locale = Locale.init(identifier: "fa_IR")

    for dateStr in dates{
        if(dateFormatter.string(from: date) == dateStr)
        {
            cell.eventIndicator.numberOfEvents = 1
            cell.eventIndicator.isHidden = false
            cell.eventIndicator.color = UIColor.blue
        }
    }             
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return eventIndex.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell =  tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
    if eventIndex.indices.contains(indexPath.row) == true {
    cell.textLabel?.text = eventIndex [indexPath.row]
    }

    return cell
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    if eventIndex.indices.contains(indexPath.row) == true {
        let text = eventIndex[indexPath.row]
        if let indexOfCellString = event.index(of: text) {
            tableViewCellNumber = indexOfCellString
        }
    }
    tblCalendar.reloadData()
           self.performSegue(withIdentifier: "infoView", sender: self)
}    

func showArabicSubTitle(date: Date!) -> String!
{
    let dateFormater = DateFormatter()
    dateFormater.dateFormat = "dd"
    dateFormater.locale = Locale(identifier: "fa_IR")

    var calendarDate = dateFormater.string(from: date as Date)        
    let characters = Array(calendarDate.characters)
    let substituteArabic = ["0":"٠", "1":"١", "2":"٢", "3":"٣", "4":"٤", "5":"٥", "6":"٦", "7":"٧", "8":"٨", "9":"٩"]
    var arabicDate =  ""

    for i in characters {
        if let subs = substituteArabic[String(i)] {
            arabicDate += subs
        } else {
            arabicDate += String(i)
        }
    }
    return arabicDate
}

//MARK: - FSCalendarDelegate
func calendar(_ calendar: FSCalendar, titleFor date: Date) -> String? {
    L102Language.setAppleLAnguageTo(lang: "fa")

    return self.showArabicSubTitle(date: date)
}

override func viewDidLoad() {

    if firstIndexRemover == true {
        eventIndex.removeAll()
        firstIndexRemover = false
    }                              
    super.viewDidLoad()

    self.calendar.firstWeekday = 7
    self.calendar.locale = Locale(identifier: "fa_IR")
    self.calendar.select(Date())
    self.calendar.identifier = NSCalendar.Identifier.persian.rawValue

    tblCalendar.delegate = self
    tblCalendar.dataSource = self
    userData = UserDefaults.standard.bool(forKey: "userData")
    if userData == true {
        event = UserDefaults.standard.object(forKey: "theEvent") as! [String]
    }else{
        event.append("رخدادی موجود نیست")
        UserDefaults.standard.set(event, forKey: "theEvent")
        if event[0] == "رخدادی موجود نیست"{
            event.remove(at:0)
            UserDefaults.standard.set(event, forKey: "theEvent")                
        }
    }        
    tblCalendar.reloadData()
    tblCalendar.backgroundColor = UIColor.lightGray
}

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    cell.backgroundColor = UIColor.clear
}

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath){
     let cell =  tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as UITableViewCell
    if editingStyle == UITableViewCellEditingStyle.delete{
        eventIndex.remove (at:indexPath.row)
        for i in 0...event.count - 1{
            let isIndexValid = event.indices.contains(i)
            if isIndexValid == true {
            if event[i] == cell.textLabel?.text{
                event.remove(at: i)
            }

        }
        }
                   UserDefaults.standard.set (event, forKey:"theEvent")
    }
    tblCalendar.reloadData()

}
func tableView(_ tableView: UITableView,
               titleForDeleteConfirmationButtonForRowAt indexPath: IndexPath) -> String?{
    return "حذف"
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}
override func viewDidAppear(_ animated: Bool){
    tblCalendar.reloadData()        
}

Answer 1

Try returning 0 in your numberOfEvents method and add your logic at willDisplayCell

The following should execute within your condition for number of events in willDisplayCell

cell.eventIndicator.numberOfEvents = 1
cell.eventIndicator.isHidden = false
cell.eventIndicator.color = UIColor.green

This method and numberOfEventsForDate is costly. To be efficient, you can limit the number of code executions by sorting your date datasource in ascending order and only execute the above code when you are inside the minimum and maximum date range. You can achieve the same using numberOfEventsForDate method, but here you can directly handle the cell's properties.

EDIT:
It seems in your updated code, you haven't reloaded your self.calendar in viewDidLoad. You have only reloaded your self.tblCalendar.

Add self.calendar.reloadData(). It should work. If not, try adding your calendar reload in main thread:

DispatchQueue.main.async { self.calendar.reloadData() }