Alphabetical sections in table table view in swift

In Swift 4 Dictionary(grouping:by:) was introduced to group a sequence to a dictionary by an arbitrary predicate.

This example maps the grouped dictionary to a custom struct Section

struct Section {    let letter : String    let names : [String]}...let usernames = ["John", "Nancy", "James", "Jenna", "Sue", "Eric", "Sam"]var sections = [Section]()override func viewDidLoad() {    super.viewDidLoad()    // group the array to ["N": ["Nancy"], "S": ["Sue", "Sam"], "J": ["John", "James", "Jenna"], "E": ["Eric"]]    let groupedDictionary = Dictionary(grouping: usernames, by: {String($0.prefix(1))})    // get the keys and sort them    let keys = groupedDictionary.keys.sorted()    // map the sorted keys to a struct    sections = keys.map{ Section(letter: $0, names: groupedDictionary[$0]!.sorted()) }    self.tableView.reloadData()}func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {    let cellID = "cell"    let cell = tableView.dequeueReusableCell(withIdentifier: cellID, for: indexPath)    let section = sections[indexPath.section]    let username = section.names[indexPath.row]    cell.textLabel?.text = username    return cell}func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {    return sections[section].names.count}func numberOfSections(in tableView: UITableView) -> Int {    return sections.count}func sectionIndexTitles(for tableView: UITableView) -> [String]? {    return sections.map{$0.letter}}func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {    return sections[section].letter}

This is how I recently implemented sorted list in a tableView in Swift programmatically,

import UIKitclass BreedController: UITableViewController{    var breeds = ["A": ["Affenpoo", "Affenpug", "Affenshire", "Affenwich", "Afghan Collie", "Afghan Hound"], "B": ["Bagle Hound", "Boxer"]]    struct Objects {        var sectionName : String!        var sectionObjects : [String]!    }    var objectArray = [Objects]()    override func viewDidLoad() {        super.viewDidLoad()        tableView.delegate = self        tableView.dataSource = self        tableView.registerClass(UITableViewCell.classForCoder(), forCellReuseIdentifier: "Cell")        // SORTING [SINCE A DICTIONARY IS AN UNSORTED LIST]        var sortedBreeds = sorted(breeds) { $0.0 < $1.0 }        for (key, value) in sortedBreeds {            println("\(key) -> \(value)")            objectArray.append(Objects(sectionName: key, sectionObjects: value))        }    }    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {        return objectArray.count    }    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {        return objectArray[section].sectionObjects.count    }    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as! UITableViewCell        // SETTING UP YOUR CELL        cell.textLabel?.text = objectArray[indexPath.section].sectionObjects[indexPath.row]        return cell    }    override func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {        return objectArray[section].sectionName    }}

Download CountryList Json file and put in side your project

https://gist.github.com/keeguon/2310008

   var json = NSArray()   var arr_name = NSArray()   var arrIndexSection : NSArray = ["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"]override func viewDidLoad() {   let path = Bundle.main.path(forResource: "countries", ofType: "json")    let data = NSData(contentsOfFile: path! )    json = (try! JSONSerialization.jsonObject(with: data as! Data, options: JSONSerialization.ReadingOptions.mutableContainers)) as! NSArray    arr_name = json.value(forKey: "name") as! NSArray;    tableview.reloadData()    super.viewDidLoad()}// Side List in tableviewpublic func numberOfSections(in tableView: UITableView) -> Int {    return 26}public func sectionIndexTitles(for tableView: UITableView) -> [String]? {    return self.arrIndexSection as? [String] //Side Section title}public func tableView(_ tableView: UITableView, sectionForSectionIndexTitle title: String, at index: Int) -> Int{    return index}public func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {    return arrIndexSection.object(at: section) as? String}// number of rows in table viewpublic func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int{    let predicate = NSPredicate(format: "SELF beginswith[c] %@", arrIndexSection.object(at: section) as! CVarArg)    let arrContacts = (arr_name as NSArray).filtered(using: predicate)    return arrContacts.count;}public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{    let cell : TableViewCell=self.tableview.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell    let predicate = NSPredicate(format: "SELF beginswith[c] %@", arrIndexSection.object(at: indexPath.section) as! CVarArg)    let arrContacts = (arr_name as NSArray).filtered(using: predicate) as NSArray    cell.textLabel?.text = arrContacts.object(at: indexPath.row) as? String    return cell}