CustomTableView.swift

struct CustomTableSection<HeaderItem, Item> {
  var header: HeaderItem
  var items: [Item]
}

struct CustomTableView<Item, Content: View, HeaderItem, HeaderContent: View>: UIViewRepresentable {
  
  @Binding
  var sections: [CustomTableSection<HeaderItem, Item>]
  
  var cellBuilder: (Item) -> Content
  var headerBuilder: (HeaderItem) -> HeaderContent

  func makeUIView(context: Context) -> UITableView {
    let collectionView = UITableView(frame: .zero, style: .plain)
    collectionView.translatesAutoresizingMaskIntoConstraints = false
    collectionView.dataSource = context.coordinator
    collectionView.delegate = context.coordinator
    collectionView.register(
      CustomTableViewHostingCell.self,
      forCellReuseIdentifier: CustomTableViewHostingCell.id
    )
    collectionView.register(
      CustomTableViewHostingHeaderCell.self,
      forHeaderFooterViewReuseIdentifier: CustomTableViewHostingHeaderCell.id
    )
    return collectionView
  }

  func updateUIView(_ uiView: UITableView, context: Context) {
    // hack to make UITableView update
    DispatchQueue.main.async {
      context.coordinator.sections = self.sections
      uiView.reloadData()
    }
  }

  func makeCoordinator() -> CustomTableViewCoordinator<Item, Content, HeaderItem, HeaderContent> {
    CustomTableViewCoordinator(
      sections: sections,
      cellBuilder: cellBuilder,
      headerBuilder: headerBuilder
    )
  }
}

class CustomTableViewCoordinator<Item, CellContent: View, HeaderItem, HeaderContent: View>: NSObject, UITableViewDataSource, UITableViewDelegate {

  var sections: [CustomTableSection<HeaderItem, Item>]
  let cellBuilder: (Item) -> CellContent
  let headerBuilder: (HeaderItem) -> HeaderContent

  init(
    sections: [CustomTableSection<HeaderItem, Item>],
    cellBuilder: @escaping (Item) -> CellContent,
    headerBuilder: @escaping (HeaderItem) -> HeaderContent
  ) {
    self.sections = sections
    self.cellBuilder = cellBuilder
    self.headerBuilder = headerBuilder
  }
  
  // MARK: - UITableViewDataSource
  
  func numberOfSections(in tableView: UITableView) -> Int {
    sections.count
  }

  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    sections[section].items.count
  }

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(
      withIdentifier: CustomTableViewHostingCell.id,
      for: indexPath
    ) as! CustomTableViewHostingCell
    
    let section = sections[indexPath.section]
    let data = section.items[indexPath.row]
    let view = cellBuilder(data)

    // create & setup hosting controller only once
    if cell.host == nil {
      let controller = UIHostingController(rootView: AnyView(view))
      cell.setupHost(with: controller)
    } else {
      // reused cell, so just set other SwiftUI root view
      cell.host?.rootView = AnyView(view)
    }
    cell.setNeedsLayout()
    return cell
  }
  
  func tableView(
    _ tableView: UITableView,
    viewForHeaderInSection section: Int
  ) -> UIView? {
    let headerView = tableView.dequeueReusableHeaderFooterView(
      withIdentifier: CustomTableViewHostingHeaderCell.id
    ) as! CustomTableViewHostingHeaderCell
    
    let section = sections[section]
    let view = headerBuilder(section.header)
    
    if headerView.host == nil {
      let controller = UIHostingController(rootView: AnyView(view))
      headerView.setupHost(with: controller)
    } else {
      // reused cell, so just set other SwiftUI root view
      headerView.host?.rootView = AnyView(view)
    }
    headerView.setNeedsLayout()
    
    return headerView
  }
}

/// Cell for holding hosting controller
private class CustomTableViewHostingCell: UITableViewCell {
  static let id: String = "CustomTableViewHostingCell"
  var host: UIHostingController<AnyView>?
  
  func setupHost(with controller: UIHostingController<AnyView>) {
    host = controller

    let cellContent = controller.view!
    cellContent.translatesAutoresizingMaskIntoConstraints = false
    contentView.addSubview(cellContent)
    NSLayoutConstraint.activate([
      cellContent.topAnchor.constraint(equalTo: contentView.topAnchor),
      cellContent.leftAnchor.constraint(equalTo: contentView.leftAnchor),
      cellContent.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
      cellContent.rightAnchor.constraint(equalTo: contentView.rightAnchor),
    ])
  }
}

/// Cell for holding hosting controller
private class CustomTableViewHostingHeaderCell: UITableViewHeaderFooterView {
  static let id: String = "CustomTableViewHostingHeaderCell"
  var host: UIHostingController<AnyView>?
  
  func setupHost(with controller: UIHostingController<AnyView>) {
    host = controller

    let cellContent = controller.view!
    cellContent.translatesAutoresizingMaskIntoConstraints = false
    contentView.addSubview(cellContent)
    NSLayoutConstraint.activate([
      cellContent.topAnchor.constraint(equalTo: contentView.topAnchor),
      cellContent.leftAnchor.constraint(equalTo: contentView.leftAnchor),
      cellContent.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
      cellContent.rightAnchor.constraint(equalTo: contentView.rightAnchor),
    ])
  }
}