Venture setup
We will use a daily storyboard-based Xcode challenge, since we’re working with UIKit.
We’re additionally going to want a desk view, for this objective we might go together with a conventional setup, however since we’re utilizing fashionable UIKit practices we will do issues only a bit completely different this time.
It is fairly unlucky that we nonetheless have to offer our personal type-safe reusable extensions for UITableView and UICollectionView lessons. Anyway, this is a fast snippet that we’ll use. ⬇️
import UIKit
extension UITableViewCell {
static var reuseIdentifier: String {
String(describing: self)
}
var reuseIdentifier: String {
kind(of: self).reuseIdentifier
}
}
extension UITableView {
func register<T: UITableViewCell>(_ kind: T.Sort) {
register(T.self, forCellReuseIdentifier: T.reuseIdentifier)
}
func reuse<T: UITableViewCell>(_ kind: T.Sort, _ indexPath: IndexPath) -> T {
dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T
}
}I’ve additionally created a subclass for UITableView, so I can configure every part contained in the initialize operate that we will want on this tutorial.
import UIKit
open class TableView: UITableView {
public init(fashion: UITableView.Fashion = .plain) {
tremendous.init(body: .zero, fashion: fashion)
initialize()
}
@out there(*, unavailable)
required public init?(coder: NSCoder) {
fatalError("init(coder:) has not been carried out")
}
open func initialize() {
translatesAutoresizingMaskIntoConstraints = false
allowsMultipleSelection = true
}
func layoutConstraints(in view: UIView) -> [NSLayoutConstraint] {
[
topAnchor.constraint(equalTo: view.topAnchor),
bottomAnchor.constraint(equalTo: view.bottomAnchor),
leadingAnchor.constraint(equalTo: view.leadingAnchor),
trailingAnchor.constraint(equalTo: view.trailingAnchor),
]
}
}We’re going to construct a settings display screen with a single choice and a a number of choice space, so it is good to have some extensions too that’ll assist us to handle the chosen desk view cells. 💡
import UIKit
public extension UITableView {
func choose(_ indexPaths: [IndexPath],
animated: Bool = true,
scrollPosition: UITableView.ScrollPosition = .none) {
for indexPath in indexPaths {
selectRow(at: indexPath, animated: animated, scrollPosition: scrollPosition)
}
}
func deselect(_ indexPaths: [IndexPath], animated: Bool = true) {
for indexPath in indexPaths {
deselectRow(at: indexPath, animated: animated)
}
}
func deselectAll(animated: Bool = true) {
deselect(indexPathsForSelectedRows ?? [], animated: animated)
}
func deselectAllInSection(besides indexPath: IndexPath) {
let indexPathsToDeselect = (indexPathsForSelectedRows ?? []).filter {
$0.part == indexPath.part && $0.row != indexPath.row
}
deselect(indexPathsToDeselect)
}
}Now we are able to give attention to making a customized cell, we’re going to use the brand new cell configuration API, however first we want a mannequin for our customized cell class.
import Basis
protocol CustomCellModel {
var textual content: String { get }
var secondaryText: String? { get }
}
extension CustomCellModel {
var secondaryText: String? { nil }
}Now we are able to use this cell mannequin and configure the CustomCell utilizing the mannequin properties. This cell could have two states, if the cell is chosen we will show a crammed examine mark icon, in any other case simply an empty circle. We additionally replace the labels utilizing the summary mannequin values. ✅
import UIKit
class CustomCell: UITableViewCell {
var mannequin: CustomCellModel?
override func updateConfiguration(utilizing state: UICellConfigurationState) {
tremendous.updateConfiguration(utilizing: state)
var contentConfig = defaultContentConfiguration().up to date(for: state)
contentConfig.textual content = mannequin?.textual content
contentConfig.secondaryText = mannequin?.secondaryText
contentConfig.imageProperties.tintColor = .systemBlue
contentConfig.picture = UIImage(systemName: "circle")
if state.isHighlighted || state.isSelected {
contentConfig.picture = UIImage(systemName: "checkmark.circle.fill")
}
contentConfiguration = contentConfig
}
}Contained in the ViewController class we are able to simply setup the newly created desk view. Since we’re utilizing a storyboard file we are able to override the init(coder:) technique this time, however if you’re instantiating the controller programmatically then you can merely create your individual init technique.
By the best way I additionally wrapped this view controller inside a navigation controller so I am show a customized title utilizing the massive fashion by default and there are some lacking code items that we have now to put in writing.
import UIKit
class ViewController: UIViewController {
var tableView: TableView
required init?(coder: NSCoder) {
self.tableView = TableView(fashion: .insetGrouped)
tremendous.init(coder: coder)
}
override func loadView() {
tremendous.loadView()
view.addSubview(tableView)
NSLayoutConstraint.activate(tableView.layoutConstraints(in: view))
}
override func viewDidLoad() {
tremendous.viewDidLoad()
title = "Desk view"
navigationController?.navigationBar.prefersLargeTitles = true
tableView.register(CustomCell.self)
tableView.delegate = self
}
override func viewDidAppear(_ animated: Bool) {
tremendous.viewDidAppear(animated)
reload()
}
func reload() {
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
}
}We do not have to implement the desk view information supply strategies, however we will use a diffable information supply for that objective, let me present you the way it works.
Diffable information supply
I’ve already included one instance containing a diffable information supply, however that was a tutorial for creating fashionable assortment views. A diffable information supply is actually an information supply tied to a view, in our case the UITableViewDiffableDataSource generic class goes to behave as an information supply object 4 our desk view. The great take into consideration these information sources is that you would be able to simply manipulate the sections and rows contained in the desk view with out the necessity of working with index paths.
So the principle concept right here is that we would wish to show two sections, one with a single choice choice for choosing a quantity, and the second choice group goes to comprise a multi-selection group with some letters from the alphabet. Listed below are the information fashions for the part gadgets.
enum NumberOption: String, CaseIterable {
case one
case two
case three
}
extension NumberOption: CustomCellModel {
var textual content: String { rawValue }
}
enum LetterOption: String, CaseIterable {
case a
case b
case c
case d
}
extension LetterOption: CustomCellModel {
var textual content: String { rawValue }
}Now we should always be capable to show these things contained in the desk view, if we implement the common information supply strategies, however since we will work with a diffable information supply we want some extra fashions. To get rid of the necessity of index paths, we are able to use a Hashable enum to outline our sections, we will have two sections, one for the numbers and one other for the letters. We will wrap the corresponding kind inside an enum with type-safe case values.
enum Part: Hashable {
case numbers
case letters
}
enum SectionItem: Hashable {
case quantity(NumberOption)
case letter(LetterOption)
}
struct SectionData {
var key: Part
var values: [SectionItem]
}We’re additionally going to introduce a SectionData helper, this fashion it will be less difficult to insert the mandatory sections and part gadgets utilizing the information supply.
last class DataSource: UITableViewDiffableDataSource<Part, SectionItem> {
init(_ tableView: UITableView) {
tremendous.init(tableView: tableView) { tableView, indexPath, itemIdentifier in
let cell = tableView.reuse(CustomCell.self, indexPath)
cell.selectionStyle = .none
change itemIdentifier {
case .quantity(let mannequin):
cell.mannequin = mannequin
case .letter(let mannequin):
cell.mannequin = mannequin
}
return cell
}
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection part: Int) -> String? {
let id = sectionIdentifier(for: part)
change id {
case .numbers:
return "Choose a quantity"
case .letters:
return "Choose some letters"
default:
return nil
}
}
func reload(_ information: [SectionData], animated: Bool = true) {
var snapshot = snapshot()
snapshot.deleteAllItems()
for merchandise in information {
snapshot.appendSections([item.key])
snapshot.appendItems(merchandise.values, toSection: merchandise.key)
}
apply(snapshot, animatingDifferences: animated)
}
}We will present a customized init technique for the information supply, the place we are able to use the cell supplier block to configure our cells with the given merchandise identifier. As you possibly can see the merchandise identifier is definitely the SectionItem enum that we created a couple of minutes in the past. We will use a change to get again the underlying mannequin, and since these fashions conform to the CustomCellModel protocol we are able to set the cell.mannequin property. Additionally it is doable to implement the common titleForHeaderInSection technique and we are able to change the part id and return a correct label for every part.
The ultimate technique is a helper, I am utilizing it to reload the information supply with the given part gadgets.
import UIKit
class ViewController: UIViewController {
var tableView: TableView
var dataSource: DataSource
required init?(coder: NSCoder) {
self.tableView = TableView(fashion: .insetGrouped)
self.dataSource = DataSource(tableView)
tremendous.init(coder: coder)
}
override func loadView() {
tremendous.loadView()
view.addSubview(tableView)
NSLayoutConstraint.activate(tableView.layoutConstraints(in: view))
}
override func viewDidLoad() {
tremendous.viewDidLoad()
title = "Desk view"
navigationController?.navigationBar.prefersLargeTitles = true
tableView.register(CustomCell.self)
tableView.delegate = self
}
override func viewDidAppear(_ animated: Bool) {
tremendous.viewDidAppear(animated)
reload()
}
func reload() {
dataSource.reload([
.init(key: .numbers, values: NumberOption.allCases.map { .number($0) }),
.init(key: .letters, values: LetterOption.allCases.map { .letter($0) }),
])
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
}
}So contained in the view controller it’s doable to render the desk view and show each sections, even the cells are selectable by default, however I might like to indicate you how one can construct a generic strategy to retailer and return chosen values, after all we might use the indexPathsForSelectedRows property, however I’ve a bit of helper device which is able to enable single and a number of choice per part. 🤔
struct SelectionOptions<T: Hashable> {
var values: [T]
var selectedValues: [T]
var multipleSelection: Bool
init(_ values: [T], chosen: [T] = [], a number of: Bool = false) {
self.values = values
self.selectedValues = chosen
self.multipleSelection = a number of
}
mutating func toggle(_ worth: T) {
guard multipleSelection else {
selectedValues = [value]
return
}
if selectedValues.comprises(worth) {
selectedValues = selectedValues.filter { $0 != worth }
}
else {
selectedValues.append(worth)
}
}
}Through the use of a generic extension on the UITableViewDiffableDataSource class we are able to flip the chosen merchandise values into index paths, it will assist us to make the cells chosen when the view masses.
import UIKit
extension UITableViewDiffableDataSource {
func selectedIndexPaths<T: Hashable>(_ choice: SelectionOptions<T>,
_ remodel: (T) -> ItemIdentifierType) -> [IndexPath] {
choice.values
.filter { choice.selectedValues.comprises($0) }
.map { remodel($0) }
.compactMap { indexPath(for: $0) }
}
}There is just one factor left to do, which is to deal with the one and a number of choice utilizing the didSelectRowAt and didDeselectRowAt delegate strategies.
import UIKit
class ViewController: UIViewController {
var tableView: TableView
var dataSource: DataSource
var singleOptions = SelectionOptions<NumberOption>(NumberOption.allCases, chosen: [.two])
var multipleOptions = SelectionOptions<LetterOption>(LetterOption.allCases, chosen: [.a, .c], a number of: true)
required init?(coder: NSCoder) {
self.tableView = TableView(fashion: .insetGrouped)
self.dataSource = DataSource(tableView)
tremendous.init(coder: coder)
}
override func loadView() {
tremendous.loadView()
view.addSubview(tableView)
NSLayoutConstraint.activate(tableView.layoutConstraints(in: view))
}
override func viewDidLoad() {
tremendous.viewDidLoad()
title = "Desk view"
navigationController?.navigationBar.prefersLargeTitles = true
tableView.register(CustomCell.self)
tableView.delegate = self
}
override func viewDidAppear(_ animated: Bool) {
tremendous.viewDidAppear(animated)
reload()
}
func reload() {
dataSource.reload([
.init(key: .numbers, values: singleOptions.values.map { .number($0) }),
.init(key: .letters, values: multipleOptions.values.map { .letter($0) }),
])
tableView.choose(dataSource.selectedIndexPaths(singleOptions) { .quantity($0) })
tableView.choose(dataSource.selectedIndexPaths(multipleOptions) { .letter($0) })
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let sectionId = dataSource.sectionIdentifier(for: indexPath.part) else {
return
}
change sectionId {
case .numbers:
guard case let .quantity(mannequin) = dataSource.itemIdentifier(for: indexPath) else {
return
}
tableView.deselectAllInSection(besides: indexPath)
singleOptions.toggle(mannequin)
print(singleOptions.selectedValues)
case .letters:
guard case let .letter(mannequin) = dataSource.itemIdentifier(for: indexPath) else {
return
}
multipleOptions.toggle(mannequin)
print(multipleOptions.selectedValues)
}
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
guard let sectionId = dataSource.sectionIdentifier(for: indexPath.part) else {
return
}
change sectionId {
case .numbers:
tableView.choose([indexPath])
case .letters:
guard case let .letter(mannequin) = dataSource.itemIdentifier(for: indexPath) else {
return
}
multipleOptions.toggle(mannequin)
print(multipleOptions.selectedValues)
}
}
}For this reason we have created the choice helper strategies at first of the article. It’s comparatively simple to implement a single and multi-selection part with this method, however after all this stuff are much more easy should you can work with SwiftUI.
Anyway, I hope this tutorial helps for a few of you, I nonetheless like UIKit so much and I am glad that Apple provides new options to it. Diffable information sources are wonderful means of configuring desk views and assortment views, with these little helpers you possibly can construct your individual settings or picker screens simply. 💪
