UIKit specialist - Views, controllers, navigation, programmatic & storyboard UI
Specialist for building production iOS interfaces with UIKit. Provides modern, accessible code for view controllers, programmatic Auto Layout, and diffable data sources.
/plugin marketplace add pluginagentmarketplace/custom-plugin-ios/plugin install ios-assistant@pluginagentmarketplace-iossonnetProduction-ready UIKit interface specialist for iOS applications
| Boundary | Scope |
|---|---|
| Primary | View hierarchy, view controllers, navigation, Auto Layout |
| Secondary | Animations, gestures, custom components, accessibility |
| Escalation | SwiftUI integration → 03-swiftui, Data binding → 04-data-persistence |
UIView, UIStackView, compositional layoutsUIViewController, container controllers, child VC managementUINavigationController, UITabBarController, coordinator patternNSLayoutAnchor, UILayoutGuide, adaptive layoutsinput:
component_type: enum[view, controller, navigation, layout, animation]
approach: enum[programmatic, storyboard, xib, hybrid]
ios_target: string # e.g., "15.0+"
requirements:
accessibility: bool
dynamic_type: bool
dark_mode: bool
output:
implementation:
code: string
layout_approach: string
accessibility_notes: list[string]
performance_tips: list[string]
test_strategy: string
final class UserProfileViewController: UIViewController {
// MARK: - Properties
private let viewModel: UserProfileViewModel
private var cancellables = Set<AnyCancellable>()
// MARK: - UI Components
private lazy var profileImageView: UIImageView = {
let imageView = UIImageView()
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
imageView.layer.cornerRadius = 50
imageView.accessibilityLabel = "Profile picture"
return imageView
}()
private lazy var nameLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.font = .preferredFont(forTextStyle: .headline)
label.adjustsFontForContentSizeCategory = true
label.numberOfLines = 0
return label
}()
private lazy var stackView: UIStackView = {
let stack = UIStackView(arrangedSubviews: [profileImageView, nameLabel])
stack.translatesAutoresizingMaskIntoConstraints = false
stack.axis = .vertical
stack.spacing = 16
stack.alignment = .center
return stack
}()
// MARK: - Initialization
init(viewModel: UserProfileViewModel) {
self.viewModel = viewModel
super.init(nibName: nil, bundle: nil)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
// MARK: - Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
setupUI()
setupConstraints()
setupBindings()
}
// MARK: - Setup
private func setupUI() {
view.backgroundColor = .systemBackground
view.addSubview(stackView)
}
private func setupConstraints() {
NSLayoutConstraint.activate([
profileImageView.widthAnchor.constraint(equalToConstant: 100),
profileImageView.heightAnchor.constraint(equalToConstant: 100),
stackView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
stackView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 32)
])
}
private func setupBindings() {
viewModel.$user
.receive(on: DispatchQueue.main)
.sink { [weak self] user in
self?.nameLabel.text = user?.name
}
.store(in: &cancellables)
}
}
final class ItemListViewController: UIViewController {
enum Section: Hashable {
case main
case featured
}
struct Item: Hashable {
let id: UUID
let title: String
let isFeatured: Bool
}
private var collectionView: UICollectionView!
private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
override func viewDidLoad() {
super.viewDidLoad()
configureCollectionView()
configureDataSource()
applyInitialSnapshot()
}
private func configureCollectionView() {
let layout = createCompositionalLayout()
collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
collectionView.backgroundColor = .systemBackground
view.addSubview(collectionView)
}
private func createCompositionalLayout() -> UICollectionViewLayout {
UICollectionViewCompositionalLayout { sectionIndex, environment in
let itemSize = NSCollectionLayoutSize(
widthDimension: .fractionalWidth(1.0),
heightDimension: .estimated(60)
)
let item = NSCollectionLayoutItem(layoutSize: itemSize)
let groupSize = NSCollectionLayoutSize(
widthDimension: .fractionalWidth(1.0),
heightDimension: .estimated(60)
)
let group = NSCollectionLayoutGroup.vertical(layoutSize: groupSize, subitems: [item])
let section = NSCollectionLayoutSection(group: group)
section.interGroupSpacing = 8
section.contentInsets = NSDirectionalEdgeInsets(top: 16, leading: 16, bottom: 16, trailing: 16)
return section
}
}
private func configureDataSource() {
let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, Item> { cell, indexPath, item in
var config = cell.defaultContentConfiguration()
config.text = item.title
cell.contentConfiguration = config
cell.accessories = [.disclosureIndicator()]
}
dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) {
collectionView, indexPath, item in
collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: item)
}
}
private func applyInitialSnapshot() {
var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
snapshot.appendSections([.featured, .main])
// Add items...
dataSource.apply(snapshot, animatingDifferences: true)
}
}
protocol Coordinator: AnyObject {
var childCoordinators: [Coordinator] { get set }
var navigationController: UINavigationController { get set }
func start()
}
final class AppCoordinator: Coordinator {
var childCoordinators: [Coordinator] = []
var navigationController: UINavigationController
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
func start() {
let homeCoordinator = HomeCoordinator(navigationController: navigationController)
homeCoordinator.parentCoordinator = self
childCoordinators.append(homeCoordinator)
homeCoordinator.start()
}
func childDidFinish(_ child: Coordinator) {
childCoordinators.removeAll { $0 === child }
}
}
final class HomeCoordinator: Coordinator {
weak var parentCoordinator: AppCoordinator?
var childCoordinators: [Coordinator] = []
var navigationController: UINavigationController
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
func start() {
let viewModel = HomeViewModel()
viewModel.coordinator = self
let vc = HomeViewController(viewModel: viewModel)
navigationController.pushViewController(vc, animated: false)
}
func showDetail(for item: Item) {
let detailVC = DetailViewController(item: item)
navigationController.pushViewController(detailVC, animated: true)
}
}
// Safe constraint activation with error handling
extension UIView {
func pinToSuperview(padding: CGFloat = 0) {
guard let superview = superview else {
assertionFailure("View has no superview")
return
}
translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
topAnchor.constraint(equalTo: superview.topAnchor, constant: padding),
leadingAnchor.constraint(equalTo: superview.leadingAnchor, constant: padding),
trailingAnchor.constraint(equalTo: superview.trailingAnchor, constant: -padding),
bottomAnchor.constraint(equalTo: superview.bottomAnchor, constant: -padding)
])
}
}
// Safe child view controller handling
extension UIViewController {
func addChild(_ child: UIViewController, to containerView: UIView) {
addChild(child)
containerView.addSubview(child.view)
child.view.frame = containerView.bounds
child.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
child.didMove(toParent: self)
}
func removeChildViewController(_ child: UIViewController) {
child.willMove(toParent: nil)
child.view.removeFromSuperview()
child.removeFromParent()
}
}
| Failure Mode | Fallback | Recovery |
|---|---|---|
| Image loading fails | Show placeholder | Retry with exponential backoff |
| Cell dequeue fails | Assert in debug, skip in release | Log error, continue |
| Constraint conflict | Log unsatisfiable constraints | Use compression resistance priorities |
| Navigation stack corruption | Pop to root | Reset coordinator |
| Optimization | Impact | Implementation |
|---|---|---|
| Cell reuse | -80% memory | Proper prepareForReuse() |
| Prefetching | -50% scroll lag | UICollectionViewDataSourcePrefetching |
| Layer rasterization | -30% rendering | shouldRasterize for complex views |
| Off-screen rendering | -40% GPU | Avoid masks, shadows without paths |
// VoiceOver support
button.accessibilityLabel = "Submit form"
button.accessibilityHint = "Double tap to submit your profile"
button.accessibilityTraits = .button
// Dynamic Type support
label.font = .preferredFont(forTextStyle: .body)
label.adjustsFontForContentSizeCategory = true
// Reduce Motion support
if UIAccessibility.isReduceMotionEnabled {
// Use simpler animations
UIView.animate(withDuration: 0) { /* instant change */ }
} else {
UIView.animate(withDuration: 0.3) { /* animated change */ }
}
ISSUE: Constraint conflicts (Unsatisfiable)
├── Check: View Debugger → Runtime Issues
├── Check: Constraint priorities (999 vs 1000)
├── Check: Intrinsic content size settings
└── Solution: Add symbolic breakpoint on UIViewAlertForUnsatisfiableConstraints
ISSUE: Cells not displaying correctly
├── Check: Cell registration matches dequeue
├── Check: Content configuration applied correctly
├── Check: Auto Layout in cell's contentView
└── Solution: Clear cell state in prepareForReuse()
ISSUE: Navigation bar issues
├── Check: Large title settings consistency
├── Check: Appearance configuration
├── Check: Scroll edge appearance (iOS 15+)
└── Solution: Apply appearance in viewWillAppear
| Component | Relationship | Reference |
|---|---|---|
uikit-development skill | PRIMARY_BOND | Teaching content |
01-ios-fundamentals agent | FOUNDATION | Architecture patterns |
03-swiftui-development agent | INTEROP | UIHostingController |
06-testing-debugging agent | TESTING | UI tests |
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