Challenge setup
We’ll use an everyday storyboard-based Xcode undertaking, since we’re working with UIKit.
We’re additionally going to wish a desk view, for this goal we may go together with a conventional setup, however since we’re utilizing fashionable UIKit practices we’ll do issues only a bit totally different this time.
It is fairly unlucky that we nonetheless have to offer our personal type-safe reusable extensions for UITableView and UICollectionView courses. Anyway, here is a fast snippet that we’ll use. ⬇️
import UIKit
extension UITableViewCell {
static var reuseIdentifier: String {
String(describing: self)
}
var reuseIdentifier: String {
sort(of: self).reuseIdentifier
}
}
extension UITableView {
func register<T: UITableViewCell>(_ sort: T.Kind) {
register(T.self, forCellReuseIdentifier: T.reuseIdentifier)
}
func reuse<T: UITableViewCell>(_ sort: 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 things contained in the initialize operate that we’ll want on this tutorial.
import UIKit
open class TableView: UITableView {
public init(type: UITableView.Fashion = .plain) {
tremendous.init(body: .zero, type: type)
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 will concentrate on 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 will use this cell mannequin and configure the CustomCell utilizing the mannequin properties. This cell can have two states, if the cell is chosen we’ll show a stuffed test 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 will simply setup the newly created desk view. Since we’re utilizing a storyboard file we will override the init(coder:) technique this time, however in case you are instantiating the controller programmatically then you may 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 type by default and there are some lacking code items that we’ve got to write down.
import UIKit
class ViewController: UIViewController {
var tableView: TableView
required init?(coder: NSCoder) {
self.tableView = TableView(type: .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’ll use a diffable information supply for that goal, 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 you can simply manipulate the sections and rows contained in the desk view with out the necessity of working with index paths.
So the primary thought right here is that we might prefer to show two sections, one with a single choice possibility for choosing a quantity, and the second possibility group goes to comprise 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 of show this stuff contained in the desk view, if we implement the common information supply strategies, however since we’ll work with a diffable information supply we want some extra fashions. To get rid of the necessity of index paths, we will use a Hashable
enum to outline our sections, we’ll have two sections, one for the numbers and one other for the letters. We’ll wrap the corresponding sort 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 is going to be simpler to insert the mandatory sections and part objects utilizing the information supply.
ultimate 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 are able to present a customized init technique for the information supply, the place we will use the cell supplier block to configure our cells with the given merchandise identifier. As you may 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 change to get again the underlying mannequin, and since these fashions conform to the CustomCellModel
protocol we will set the cell.mannequin
property. Additionally it is attainable to implement the common titleForHeaderInSection
technique and we will 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 objects.
import UIKit
class ViewController: UIViewController {
var tableView: TableView
var dataSource: DataSource
required init?(coder: NSCoder) {
self.tableView = TableView(type: .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 would like to indicate you learn how to construct a generic strategy to retailer and return chosen values, after all we may use the indexPathsForSelectedRows
property, however I’ve slightly helper device which can 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.accommodates(worth) {
selectedValues = selectedValues.filter { $0 != worth }
}
else {
selectedValues.append(worth)
}
}
}
By utilizing a generic extension on the UITableViewDiffableDataSource
class we will flip the chosen merchandise values into index paths, this can 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.accommodates($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(type: .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 straightforward to implement a single and multi-selection part with this method, however after all these items are much more easy when you can work with SwiftUI.
Anyway, I hope this tutorial helps for a few of you, I nonetheless like UIKit lots and I am glad that Apple provides new options to it. Diffable information sources are glorious means of configuring desk views and assortment views, with these little helpers you may construct your individual settings or picker screens simply. 💪