ReloadData in UICollectionView - swift

Question

I use CoreData and want to reload the UICollectionView when I save a new entry in CoreData but the only self.collectionview.reloaddata()don´t run it reload nothing.
Thanks for your Help.
My CoreData and UICollectionView I have try it to reload the UICollectionView when clockblogalarm become a new entry:
var clockblogalarm = [ClockBlogAlarm] () {
didSet { //self.ClockCollectionView.reloadData()
}
}
var mgdContext = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
func loadClockAlarms () {
let LoadRequestBlogAlarm: NSFetchRequest<ClockBlogAlarm> = ClockBlogAlarm.fetchRequest()
clockblogalarm = try! mgdContext.fetch(LoadRequestBlogAlarm as! NSFetchRequest<NSFetchRequestResult>) as! [ClockBlogAlarm]
}
#IBOutlet var ClockCollectionView: UICollectionView!
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.loadClockAlarms()
}
Here I save the Entry in CoreData. When I click the Button Done view.bottomButtonHandler{} then I want to reload the data and show it in the UICollectionView with loadClockAlarms() .
else if index == 1 {
let view = AddClockView.instantiateFromNib()
let window = UIApplication.shared.delegate?.window!
view.closeButtonHandler = {[weak modal] in
modal?.closeWithLeansRandom()
return
}
view.bottomButtonHandler = {[weak modal] in
modal?.closeWithLeansRandom()
self.loadClockAlarms()
return
}
modal.show(modalView: view, inView: window!)
}
// MARK: UICollectionViewDataSource
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return clockblogalarm.count
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "AlarmBlogCell", for: indexPath) as! AlarmBlogCell
cell.layer.cornerRadius = 8
let clockblogalarms = clockblogalarm[indexPath.row]
if clockblogalarms.lock == "ClockblogAlarm" {
cell.Title.text = clockblogalarms.title
cell.Time.text = "SSSSS"
}
return cell
}

Answer 1

swift 5 & 4.2:
DispatchQueue.main.async {
self.collectionView.reloadData()
}

Answer 2

Ensure the reloadData() is called in the main thread, as it is the UI-responsible action:
dispatch_async(dispatch_get_main_queue()) {
self.ClockCollectionView.reloadData()
}