Open Radar

 
Area:
UIKit

Summary:
A table view with section index titles cannot have  a single section index title consisting of the • character. 

Steps to Reproduce:
Set up a table view with one section and return section title and section index titles where the single section title is "•". If any other section index title except • is returned alongside the existing index title, the table view behaves as expected.
See attached file. Can be pasted over MasterViewController.swift from a default Master-Detail iOS app created with Xcode.

Expected Results:
The table will show the dot character as a section index title on the right of the table view.

Actual Results:
The application crashes with the following exception:
*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
*** First throw call stack:
(
	0   CoreFoundation                      0x0000000103e6fb0b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x00000001038db141 objc_exception_throw + 48
	2   CoreFoundation                      0x0000000103da4ffb -[__NSArrayM objectAtIndex:] + 203
	3   UIKit                               0x000000010469526b -[UITableViewIndex _displayTitles] + 292
	4   UIKit                               0x0000000104695692 -[UITableViewIndex _cacheAndMeasureTitles] + 165
	5   UIKit                               0x00000001046967b6 -[UITableViewIndex setTitles:] + 119
	6   UIKit                               0x00000001043cca09 -[UITableView _updateIndexDisplayedTitles] + 65
	7   UIKit                               0x00000001043ccf90 -[UITableView _updateIndex] + 308
	8   UIKit                               0x00000001043e5ede -[UITableView noteNumberOfRowsChanged] + 159
	9   UIKit                               0x00000001043e5508 -[UITableView reloadData] + 2013

Version/Build:
iOS 10.3.3

Attached file:
import UIKit

class MasterViewController: UITableViewController {

    var detailViewController: DetailViewController? = nil
    var objects = [Any]()


    override func viewDidLoad() {
        super.viewDidLoad()

        for  _ in 0..<10 {
            objects.insert(NSDate(), at: 0)
        }
        tableView.reloadData()
    }
    
    func insertNewObject(_ sender: Any) {
        objects.insert(NSDate(), at: 0)
    }
    
    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return sectionIndexTitles(for: tableView)![section]
    }
    
    override func sectionIndexTitles(for tableView: UITableView) -> [String]? {
        return [
            "•", // this will crash. uncomment the line below and it will not crash any more.
//            "A",
        ]
    }

    override func numberOfSections(in tableView: UITableView) -> Int {
        return sectionIndexTitles(for: tableView)!.count
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return objects.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

        let object = objects[indexPath.row] as! NSDate
        cell.textLabel!.text = object.description
        return cell
    }
}