swipe tableViewCell to delete an item - swift

Question

I want to delete a Unit from my Core Data Application. When user presses delete button on the Cell, I present a warning.
the code was
let alert = UIAlertController(title: "Warning!", message: "Are you sure to delete \"\(currentUnit)\" and all of its containing objects?", preferredStyle: .Alert)
I wanted to update the warning message with the objects count so I wrote
currentUnitObjectsCount = getSelectedUnitObjectsCount() //Which connects to database and returns just an integer
let deleteAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "Delete",handler: { (action, indexPath) -> Void in
let currentUnit = self.units[indexPath.row].title!
let alert = UIAlertController(title: "Warning!", message: "Are you sure to delete \"\(currentUnit)\" and all of its \(currentUnitObjectsCount) containing objects?", preferredStyle: .Alert)
let yesAction = UIAlertAction(title: "Yes", style: .Default) /* handler: { (action : UIAlertAction) -> Void in */ { (action : UIAlertAction) in
if let managedObjectContext = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext{
let unitToDelete = self.fetchResultController.objectAtIndexPath(indexPath) as! Unit
managedObjectContext.deleteObject(unitToDelete)
do{
try managedObjectContext.save()
}catch{
print(error)
}
}
self.checkUnits()
}
let noAction = UIAlertAction(title: "No", style: UIAlertActionStyle.Default, handler: {
(action : UIAlertAction!) -> Void in
tableView.reloadData() //to return the tableView to its normal view
})
alert.addAction(yesAction)
alert.addAction(noAction)
self.presentViewController(alert, animated: true, completion: nil)
})
deleteAction.backgroundColor = UIColor.redColor()
return [editAction]
}
Now when i swipe the tableViewCell, it swipes but the delete button does not appear but when I tap the Delete button position in the swiped cell, the warning appears which means the button is there but I cant see it.
returning the code to the first style every thing works fine, but the second one acts very strange.
When I put this line of code
currentUnitObjectsCount = getSelectedUnitObjectsCount() //Which connects to database and returns just an integer
just after the the
let deleteAction = ...
currentUnitObjectsCount = getSelectedUnitObjectsCount()
let currentUnit = self.units[indexPath.row].title!
.
.
.
and swipe a cell, rows of the table disappear
I dont find why these happen.