The following is a UIKit app with a collection view with one section, whose supplementary view sports a search bar.
When you type, it often resigns first responder.
import UIKit
class ViewController: UIViewController {
let words = ["foo", "bar"]
var filteredWords = ["foo", "bar"] {
didSet {
dataSource.apply(self.snapshot)
}
}
var collectionView: UICollectionView!
var dataSource: UICollectionViewDiffableDataSource<String, String>!
var snapshot: NSDiffableDataSourceSnapshot<String, String> {
var snapshot = NSDiffableDataSourceSnapshot<String, String>()
snapshot.appendSections(["main"])
snapshot.appendItems(filteredWords)
return snapshot
}
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.rightBarButtonItem = .init(title: "Apply", style: .plain, target: self, action: #selector(apply))
configureHierarchy()
configureDataSource()
}
@objc func apply() {
dataSource.apply(self.snapshot)
}
func configureHierarchy() {
collectionView = .init(frame: .zero, collectionViewLayout: createLayout())
view.addSubview(collectionView)
collectionView.frame = view.bounds
collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
}
func createLayout() -> UICollectionViewLayout {
UICollectionViewCompositionalLayout { section, layoutEnvironment in
var config = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
config.headerMode = .supplementary
return NSCollectionLayoutSection.list(using: config, layoutEnvironment: layoutEnvironment)
}
}
func configureDataSource() {
let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, String> { _, _, _ in }
dataSource = .init(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: itemIdentifier)
}
let searchbarHeaderRegistration = UICollectionView.SupplementaryRegistration<SearchBarCell>(elementKind: UICollectionView.elementKindSectionHeader) { cell, elementKind, indexPath in
cell.searchBar.delegate = self
}
dataSource.supplementaryViewProvider = { collectionView, kind, indexPath in
collectionView.dequeueConfiguredReusableSupplementary(using: searchbarHeaderRegistration, for: indexPath)
}
dataSource.apply(self.snapshot, animatingDifferences: false)
}
}
extension ViewController: UISearchBarDelegate {
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
DispatchQueue.main.async { [weak self] in
guard let self else { return }
filteredWords = words.filter { $0.hasPrefix(searchText) }
}
}
func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {
DispatchQueue.main.async { [weak self] in
guard let self else { return }
filteredWords = words
}
}
}
class SearchBarCell: UICollectionViewListCell {
let searchBar = UISearchBar()
override init(frame: CGRect) {
super.init(frame: frame)
contentView.addSubview(searchBar)
searchBar.pinToSuperview()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
extension UIView {
func pin(
to object: CanBePinnedTo,
top: CGFloat = 0,
bottom: CGFloat = 0,
leading: CGFloat = 0,
trailing: CGFloat = 0
) {
self.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
self.topAnchor.constraint(equalTo: object.topAnchor, constant: top),
self.bottomAnchor.constraint(equalTo: object.bottomAnchor, constant: bottom),
self.leadingAnchor.constraint(equalTo: object.leadingAnchor, constant: leading),
self.trailingAnchor.constraint(equalTo: object.trailingAnchor, constant: trailing),
])
}
func pinToSuperview(
top: CGFloat = 0,
bottom: CGFloat = 0,
leading: CGFloat = 0,
trailing: CGFloat = 0,
file: StaticString = #file,
line: UInt = #line
) {
guard let superview = self.superview else {
print(">> \(#function) failed in file: \(String.localFilePath(from: file)), at line: \(line): could not find \(Self.self).superView.")
return
}
self.pin(to: superview, top: top, bottom: bottom, leading: leading, trailing: trailing)
}
func pinToSuperview(constant c: CGFloat = 0, file: StaticString = #file, line: UInt = #line) {
self.pinToSuperview(top: c, bottom: -c, leading: c, trailing: -c, file: file, line: line)
}
}
@MainActor
protocol CanBePinnedTo {
var topAnchor: NSLayoutYAxisAnchor { get }
var bottomAnchor: NSLayoutYAxisAnchor { get }
var leadingAnchor: NSLayoutXAxisAnchor { get }
var trailingAnchor: NSLayoutXAxisAnchor { get }
}
extension UIView: CanBePinnedTo { }
extension UILayoutGuide: CanBePinnedTo { }
extension String {
static func localFilePath(from fullFilePath: StaticString = #file) -> Self {
URL(fileURLWithPath: "\(fullFilePath)").lastPathComponent
}
}
By the way if you remove the dispatch blocks, the app simply crashes complaining that you're trying to apply datasource snapshots from both the main queue and other queues.
Xcode 15.3 iOS 17.4 simulator, MacBook Air M1 8GB macOS Sonoma 14.4.1
