Adding index at uitableview is not working in Swift 2.0

I am loading contacts in UITableView and I want to add index at the right end for user to navigate through contacts. I am using the code: var indexOfNames = [String]() let indexNames = "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z" indexOfNames = indexNames.componentsSeparatedByString(" ") func sectionIndexTitlesForTableView(tableView: UITableView) -> [String]? { return indexOfNames } func