TableView reloads the same content over again when populated through the unwind segue

1. I have 2 structs for the data to be passed to the tableView:

    struct Session {
        let dateModel: Date?
        let timeBegModel: Date?
        let timeEndModel: Date?
        let sessionModel: String?
        let venueModel: String?
        var formattedTimeBeg: String {
            guard let text = timeBegModel else {
                return ""
            }
            return DateFormatter.adjustedTimeFormat.string(from: text)
        }
        var formattedTimeEnd: String {
            guard let text = timeEndModel else {
                return ""
            }
            return DateFormatter.adjustedTimeFormat.string(from: text)
        }
    }
   

2. The data is passed from another viewController with unwind segue:

    @IBAction func unwindToMainVC(segue: UIStoryboardSegue) {
        guard let vc = segue.source as? AddSessionVC else { return }
        guard let date = vc.dateDP?.date, let timeBeg = vc.timeBegDP?.date, let timeEnd = vc.timeEndDP?.date, let session = vc.sessionTF.text, let venue = vc.venueTF.text else { return }
    let Session = Session(dateModel: date, timeBegModel: timeBeg, timeEndModel: timeEnd, sessionModel: session, venueModel: venue)
    sessions.append(Session)
    sessions.sort { $0.timeBegModel! < $1.timeEndModel! }
    sortByDate() // I tried to put this func in the viewDidLoad(), but it doesn't work
    tableView.reloadData()
    }
   

3. I have a function to set up the date as a tableView section header:

    func sortByDate() {
        let datesInSessions = sessions.reduce(into: Set<Date>()) { result, sessions in
            let dateInSession = Calendar.current.startOfDay(for: sessions.dateModel!)
            result.insert(dateInSession)
        }
        for dateInSession in datesInSessions {
            let dateComp = Calendar.current.dateComponents([.year, .month, .day], from: dateInSession)
            var sortedContent: [Session] = []
            sessions.forEach { sessions in
                let contComp = Calendar.current.dateComponents([.year, .month, .day], from: sessions.dateModel!)
                if contComp == dateComp {
                    sortedContent.append(sessions)
                }
            }
            let newSection = Section(sectionDate: dateInSession, sessions: sortedContent)
            sections.append(newSection)
        }
    }
   

The problem is that whenever I add a new cell (with the same date as the previous cell), the section with the exact same date creates all over again (see the picture).

How do I fix this?

Thanks to an outside help from @OlzhasAkhmetov from MobiDev I was able to fix the repetition of sections and cells.

The sortByDate() function required sections.removeAll() in the very beginning. The final working code of the sortByDate() is as follows:

func sortByDate() {
    sections.removeAll() // This is what was missing
    let dates = sessions.reduce(into: Set<Date>()) { result, sessions in
        let date = Calendar.current.startOfDay(for: sessions.dateModel!)
        result.insert(date) }
    for date in dates {
        let dateComp = Calendar.current.dateComponents([.year, .month, .day], from: date)
        var sortedContent: [Session] = []
        sessions.forEach { sessions in
            let contComp = Calendar.current.dateComponents([.year, .month, .day], from: sessions.dateModel!)
            if contComp == dateComp {
                sortedContent.append(sessions) } }
        let newSection = Section(sectionDate: date, sessions: sortedContent)
        sections.append(newSection) } }