A SwiftUI wrapper of UICollectionView that manages an ordered collection of data items and presents them using customizable layouts.

CollectionViewRepresentable.swift

//
//  CollectionViewRepresentable.swift
//
//
//  Created by Satish Vekariya on 12/11/2023.
//

import SwiftUI
import UIKit

/// A SwiftUI wrapper of UICollectionView  that manages an ordered collection of data items and presents them using customizable layouts.
public struct CollectionViewRepresentable<Item, Content: View>: UIViewRepresentable {
    @Binding var items: [Item]
    let layout: LayoutKind
    let alwaysBounceVertical: Bool
    
    /// SwiftUI view provider
    let contentProvider: (Item, IndexPath) -> Content
    
    // Helper Callbacks
    let shouldHighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> Bool)?
    let didHighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())?
    let didUnhighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())?
    let shouldSelectItemAt: ((UICollectionViewCell?, Item, IndexPath) -> Bool)?
    let didSelectItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())?

    public init(
        _ items: Binding<[Item]>,
        layout: LayoutKind,
        alwaysBounceVertical: Bool = false,
        @ViewBuilder contentProvider: @escaping (Item, IndexPath) -> Content,
        shouldHighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> Bool)? = nil,
        didHighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())? = nil,
        didUnhighlightItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())? = nil,
        shouldSelectItemAt: ((UICollectionViewCell?, Item, IndexPath) -> Bool)? = nil,
        didSelectItemAt: ((UICollectionViewCell?, Item, IndexPath) -> ())? = nil
    ) {
        self._items = items
        self.layout = layout
        self.alwaysBounceVertical = alwaysBounceVertical
        self.contentProvider = contentProvider
        self.shouldHighlightItemAt = shouldHighlightItemAt
        self.didHighlightItemAt = didHighlightItemAt
        self.didUnhighlightItemAt = didUnhighlightItemAt
        self.shouldSelectItemAt = shouldSelectItemAt
        self.didSelectItemAt = didSelectItemAt
    }

    public func makeUIView(context: Context) -> UICollectionView {
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout.create())
        collectionView.dataSource = context.coordinator
        collectionView.delegate = context.coordinator
        collectionView.alwaysBounceVertical = alwaysBounceVertical
        collectionView.backgroundColor = nil
        
        return collectionView
    }

    public func updateUIView(_ uiView: UICollectionView, context: Context) {
        uiView.reloadData()
    }

    // Create a coordinator to handle the data source and delegate
    public func makeCoordinator() -> Coordinator {
        return Coordinator(self)
    }
    
    public class Coordinator: NSObject, UICollectionViewDataSource, UICollectionViewDelegate {
        var parent: CollectionViewRepresentable
        
        private var userInteractionCellRegistration: UICollectionView.CellRegistration<UICollectionViewListCell, Item>!
        
        init(_ parent: CollectionViewRepresentable) {
            self.parent = parent
            super.init()
            
            userInteractionCellRegistration = .init { [unowned self] cell, indexPath, item in
                cell.contentConfiguration = UIHostingConfiguration {
                    self.parent.contentProvider(item, indexPath)
                }
                .margins(.all, 0)
                cell.backgroundConfiguration = .clear()
            }
        }

        // UICollectionViewDataSource methods
        public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            return parent.items.count
        }

        public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
            let item = parent.items[indexPath.row]
            let cell = collectionView.dequeueConfiguredReusableCell(
                using: userInteractionCellRegistration,
                for: indexPath,
                item: item
            )
            return cell
        }
        
        public func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool {
            let cell = collectionView.cellForItem(at: indexPath)
            let item = parent.items[indexPath.row]
            return parent.shouldHighlightItemAt?(cell, item, indexPath) ?? false
        }
        
        public func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
            let cell = collectionView.cellForItem(at: indexPath)
            let item = parent.items[indexPath.row]
            parent.didHighlightItemAt?(cell, item, indexPath)
        }

        public func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
            let cell = collectionView.cellForItem(at: indexPath)
            let item = parent.items[indexPath.row]
            parent.didUnhighlightItemAt?(cell, item, indexPath)
        }
        
        public func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
            let cell = collectionView.cellForItem(at: indexPath)
            let item = parent.items[indexPath.row]
            return parent.shouldHighlightItemAt?(cell, item, indexPath) ?? true
        }
        
        public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
            let cell = collectionView.cellForItem(at: indexPath)
            let item = parent.items[indexPath.row]
            parent.didSelectItemAt?(cell, item, indexPath)
        }
    }
}

extension CollectionViewRepresentable {
    public enum LayoutKind {
        case list(appearance: UICollectionLayoutListConfiguration.Appearance)
        case carousel
        
        func create() -> UICollectionViewLayout {
            switch self {
            case .list(let appearance):
                return UICollectionViewCompositionalLayout.list(using: .init(appearance: appearance))
            case .carousel:
                return CarouselLayoutGenerator.create()
            }
        }
    }
}