Challenge setup
We will use a daily storyboard-based Xcode undertaking, since we’re working with UIKit.
We’re additionally going to wish a desk view, for this function we may go along with a conventional setup, however since we’re utilizing trendy UIKit practices we will do issues only a bit totally different this time.
It is fairly unlucky that we nonetheless have to supply our personal type-safe reusable extensions for UITableView and UICollectionView lessons. Anyway, here 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.Kind) {
register(T.self, forCellReuseIdentifier: T.reuseIdentifier)
}
func reuse<T: UITableViewCell>(_ kind: T.Kind, _ indexPath: IndexPath) -> T {
dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T
}
}I’ve additionally created a subclass for UITableView, so I can configure all the pieces contained in the initialize operate that we will want on this tutorial.
import UIKit
open class TableView: UITableView {
public init(fashion: UITableView.Model = .plain) {
tremendous.init(body: .zero, fashion: fashion)
initialize()
}
@accessible(*, 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 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 can have two states, if the cell is chosen we will show a stuffed 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 in case you are instantiating the controller programmatically then you might 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 big fashion by default and there are some lacking code items that we’ve got 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 knowledge supply strategies, however we will use a diffable knowledge supply for that function, let me present you the way it works.
Diffable knowledge supply
I’ve already included one instance containing a diffable knowledge supply, however that was a tutorial for creating trendy assortment views. A diffable knowledge supply is actually a knowledge supply tied to a view, in our case the UITableViewDiffableDataSource generic class goes to behave as a knowledge supply object 4 our desk view. The great take into consideration these knowledge sources is you can simply manipulate the sections and rows contained in the desk view with out the necessity of working with index paths.
So the principle thought right here is that we would prefer to show two sections, one with a single choice choice for choosing a quantity, and the second choice group goes to include a multi-selection group with some letters from the alphabet. Listed here are the information fashions for the part objects.
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 must always be capable to show these things contained in the desk view, if we implement the common knowledge supply strategies, however since we will work with a diffable knowledge supply we want some further fashions. To eradicate 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 manner it will be simpler to insert the mandatory sections and part objects 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
swap 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)
swap id {
case .numbers:
return "Choose a quantity"
case .letters:
return "Choose some letters"
default:
return nil
}
}
func reload(_ knowledge: [SectionData], animated: Bool = true) {
var snapshot = snapshot()
snapshot.deleteAllItems()
for merchandise in knowledge {
snapshot.appendSections([item.key])
snapshot.appendItems(merchandise.values, toSection: merchandise.key)
}
apply(snapshot, animatingDifferences: animated)
}
}We are able to 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 are able to use a swap to get again the underlying mannequin, and since these fashions conform to the CustomCellModel protocol we are able to set the cell.mannequin property. It is usually attainable to implement the common titleForHeaderInSection technique and we are able to swap 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 objects.
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 attainable to render the desk view and show each sections, even the cells are selectable by default, however I might like to indicate you methods to construct a generic method to retailer and return chosen values, after all we may use the indexPathsForSelectedRows property, however I’ve just a little helper device which is able to permit 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.incorporates(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, this can assist us to make the cells chosen when the view hundreds.
import UIKit
extension UITableViewDiffableDataSource {
func selectedIndexPaths<T: Hashable>(_ choice: SelectionOptions<T>,
_ remodel: (T) -> ItemIdentifierType) -> [IndexPath] {
choice.values
.filter { choice.selectedValues.incorporates($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
}
swap 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
}
swap 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)
}
}
}That is why we have created the choice helper strategies to start with of the article. It’s comparatively straightforward to implement a single and multi-selection part with this method, however after all these items are much more easy if you happen to can work with SwiftUI.
Anyway, I hope this tutorial helps for a few of you, I nonetheless like UIKit rather a lot and I am glad that Apple provides new options to it. Diffable knowledge sources are wonderful manner of configuring desk views and assortment views, with these little helpers you possibly can construct your individual settings or picker screens simply. 💪