Challenge setup
We’ll use a daily storyboard-based Xcode mission, since we’re working with UIKit.
We’re additionally going to want a desk view, for this goal we might go together with a traditional 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 offer 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
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 pieces contained in the initialize operate that we will want on this tutorial.
import UIKit
open class TableView: UITableView
public init(type: UITableView.Type = .plain)
tremendous.init(body: .zero, type: type)
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 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’d like 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 will 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
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 if you’re instantiating the controller programmatically then you can merely create your individual init technique.
By the way in which I additionally wrapped this view controller inside a navigation controller so I am show a customized title utilizing the big type by default and there are some lacking code items that now we have 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 knowledge supply strategies, however we will use a diffable knowledge supply for that goal, 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 modern collection 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 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 here are the info 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 should 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’d like some extra fashions. To get rid of the necessity of index paths, we will use a Hashable enum to outline our sections, we will 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 manner it will be easier to insert the mandatory sections and part objects utilizing the info supply.
closing 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 "Decide a quantity"
case .letters:
return "Decide 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 info supply, the place we will use the cell supplier block to configure our cells with the given merchandise identifier. As you’ll be able to 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. It is usually 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 info 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 might like to point out you methods to construct a generic strategy to retailer and return chosen values, after all we might use the indexPathsForSelectedRows property, however I’ve just a little helper instrument which can 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.comprises(worth)
selectedValues = selectedValues.filter $0 != worth
else
selectedValues.append(worth)
Through the use of a generic extension on the UITableViewDiffableDataSource class we will flip the chosen merchandise values into index paths, it will assist us to make the cells chosen when the view hundreds.
import UIKit
extension UITableViewDiffableDataSource
func selectedIndexPaths<T: Hashable>(_ choice: SelectionOptions<T>,
_ rework: (T) -> ItemIdentifierType) -> [IndexPath]
choice.values
.filter choice.selectedValues.comprises($0)
.map rework($0)
.compactMap indexPath(for: $0)
There is just one factor left to do, which is to deal with the only 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)
Because of this we have created the choice helper strategies to start with of the article. It’s comparatively simple to implement a single and multi-selection part with this system, however after all this stuff are much more easy in the event you can work with SwiftUI.
Anyway, I hope this tutorial helps for a few of you, I nonetheless like UIKit loads and I am glad that Apple provides new options to it. Diffable knowledge sources are glorious approach of configuring desk views and assortment views, with these little helpers you’ll be able to construct your individual settings or picker screens simply. 💪
