Minimum letter for string sorting - ios

Question

Question:
I have Strings: "A", "C", "D", "1", "И" (Russian), "你" (Chinese). And I have string let alwaysFirstString = "?"
I want alwaysFirstString to be always first when I use general iOS sorting. What should be the alwaysFirstString instead of "?" ?
Why I need that:
In my application I display contacts like in Telegram application:
At first I need to display contacts that have their own contacts in my application (server returns me these contacts)
After that I display other contacts (grouped by the first letter in their surname)
I display contacts in group UITableView. So in my DBContact object in core data I have sectionInfo field. Usually this field = A, B, C, F (The first letter of surname), but for some contacts (I want them to be always first) I need to have other symbol. So this symbol should always be the first when I use regular sortDesctriptors in FetchResultController (better for all languages).
Here is the code:
let entityName = kDBContact
let fetchRequest = NSFetchRequest<DBContact>(entityName: entityName)
// let entityDescription = NSEntityDescription.entity(forEntityName: entityName, in: DatabaseManager.sharedInstance.managedObjectContext)
// fetchRequest.entity = entityDescription
fetchRequest.fetchBatchSize = 20
// sort
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "sectionInfo", ascending: true), NSSortDescriptor(key: "nameAndSurname", ascending: true)]
// sometimes we have predicate when user tries to search smth
var predicate: NSPredicate?
var formatForPredicate = ""
// filter not to show fake contacts
formatForPredicate += "(isFakeContact == false)"
var argumentArray = [AnyObject]()
// text filter in search bar
if help_needToShowFilteredContacts() {
if formatForPredicate.length > 0 {
formatForPredicate += " AND "
}
formatForPredicate += "((nameAndSurname CONTAINS[cd] %#) OR (phoneNumbers.numberOnlyDigits CONTAINS[cd] %#))"
argumentArray.append(resultSearchController.searchBar.text! as AnyObject)
argumentArray.append(resultSearchController.searchBar.text! as AnyObject)
}
sectionNameKeyPath = "sectionInfo"
// filter to show only favourites
if segmentedControl.selectedSegmentIndex == segmented_favouriteIndex {
sectionNameKeyPath = nil
if formatForPredicate.length > 0 {
formatForPredicate += " AND "
}
formatForPredicate += "(isFavourite == true)"
}
if formatForPredicate.length > 0 {
predicate = NSPredicate(format: formatForPredicate, argumentArray: argumentArray)
}
fetchRequest.predicate = predicate
self.fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest as! NSFetchRequest<NSFetchRequestResult>, managedObjectContext: DatabaseManager.sharedInstance.managedObjectContext, sectionNameKeyPath: sectionNameKeyPath, cacheName: nil)
So you can see fetchRequest.sortDescriptors = [NSSortDescriptor(key: "sectionInfo", ascending: true), NSSortDescriptor(key: "nameAndSurname", ascending: true)] . So in sectionInfo I have this First characters of the surname, and I want registered contacts (with special character in sectionInfo) to be always the 1st.

Answer 1

I used "" for maximum symbol and " " for minimum. Later in fetched result controller delegate I have:
func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
if let sections = fetchedResultsController?.sections {
let currentSection = sections[section]
let name = currentSection.name
if "" == name {
return "#"
}
else if " " == name {
return "Registered contacts"
}
return name
}
return nil
}
I found last symbol here What character to use to put an item at the end of an alphabetic list?