Alphabetical sections in table table view in swift

Question

I have a list of names sorted alphabetically, and now I want display these names in a table view. I'm struggling with grouping these names for each letter.

My code looks like this:

let sections:Array<AnyObject> = ["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"] var usernames = [String]()  func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{          let cellID = "cell"          let cell: UITableViewCell = self.tv.dequeueReusableCellWithIdentifier(cellID) as UITableViewCell          cell.textLabel?.text = usernames[indexPath.row]      return cell }  func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int{          return usernames.count } func numberOfSectionsInTableView(tableView: UITableView) -> Int{          return 26 }   func sectionIndexTitlesForTableView(tableView: UITableView) -> [AnyObject]!{          return self.sections }  func tableView(tableView: UITableView,     sectionForSectionIndexTitle title: String,     atIndex index: Int) -> Int{                  return index }  func tableView(tableView: UITableView,     titleForHeaderInSection section: Int) -> String?{                  return self.sections[section] as? String } 

and it all works pretty good except for the grouping which makes my table view end up like this:

So I know you should be able to use the filtered function in an Array, but I did not understand how to implement it.

Any suggestions on how to proceed would be appreciated.

Answer 1

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 } 

Answer 2

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

import UIKit  class 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     }   }