iOS Development

Working with diffable knowledge sources and desk views utilizing UIKit

Written by admin


Mission 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 goal we might go along 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, 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.Fashion = .plain) {
        tremendous.init(body: .zero, type: type)
        
        initialize()
    }

    @obtainable(*, 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 verify 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:) methodology this time, however if you’re instantiating the controller programmatically then you could possibly merely create your individual init methodology.


By the way in which 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 jot 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 fashionable 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 nice 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 primary concept right here is that we might prefer 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 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 must always be capable of show this stuff 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 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 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’ll be easier to insert the required sections and part objects utilizing the info supply.


remaining 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 methodology for the info supply, the place we are able to 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 are able to set the cell.mannequin property. Additionally it is doable to implement the common titleForHeaderInSection methodology and we are able to change the part id and return a correct label for every part.


The ultimate methodology 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 doable to render the desk view and show each sections, even the cells are selectable by default, however I might like to indicate you construct a generic method to retailer and return chosen values, after all we might use the indexPathsForSelectedRows property, however I’ve a little bit helper instrument 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.accommodates(worth) {
            selectedValues = selectedValues.filter { $0 != worth }
        }
        else {
            selectedValues.append(worth)
        }
    }
}


By utilizing 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 hundreds.


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 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 method of configuring desk views and assortment views, with these little helpers you’ll be able to construct your individual settings or picker screens simply. 💪



About the author

admin

Leave a Comment