Initial commit: add all skills files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ios-application-dev/references/layout-system.md

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+# Layout System
+
+iOS layout system guide covering touch targets, safe areas, UICollectionView, and Compositional Layout.
+
+## Touch Targets
+
+Interactive elements need adequate tap areas. The recommended minimum is 44x44 points.
+
+```swift
+let actionButton = UIButton(type: .system)
+actionButton.setTitle("Submit", for: .normal)
+view.addSubview(actionButton)
+
+actionButton.snp.makeConstraints { make in
+    make.height.greaterThanOrEqualTo(44)
+    make.leading.trailing.equalToSuperview().inset(16)
+    make.bottom.equalTo(view.safeAreaLayoutGuide).offset(-16)
+}
+```
+
+Use 8-point increments for spacing (8, 16, 24, 32, 40, 48) to maintain visual consistency.
+
+## Safe Area
+
+Always constrain content to the safe area to avoid the notch, Dynamic Island, and home indicator.
+
+```swift
+class MainViewController: UIViewController {
+    private let contentStack = UIStackView()
+    
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        view.backgroundColor = .systemBackground
+        
+        contentStack.axis = .vertical
+        contentStack.spacing = 16
+        view.addSubview(contentStack)
+        
+        contentStack.snp.makeConstraints { make in
+            make.top.bottom.equalTo(view.safeAreaLayoutGuide)
+            make.leading.trailing.equalTo(view.safeAreaLayoutGuide).inset(16)
+        }
+    }
+}
+```
+
+## UICollectionView with Diffable Data Source
+
+```swift
+class ItemsViewController: UIViewController {
+    enum Section { case main }
+    
+    private var collectionView: UICollectionView!
+    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
+    
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        setupCollectionView()
+        configureDataSource()
+    }
+    
+    private func setupCollectionView() {
+        var config = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
+        config.trailingSwipeActionsConfigurationProvider = { [weak self] indexPath in
+            self?.makeSwipeActions(for: indexPath)
+        }
+        
+        let layout = UICollectionViewCompositionalLayout.list(using: config)
+        collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
+        
+        view.addSubview(collectionView)
+        collectionView.snp.makeConstraints { make in
+            make.edges.equalToSuperview()
+        }
+    }
+    
+    private func configureDataSource() {
+        let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, Item> { 
+            cell, indexPath, item in
+            var content = cell.defaultContentConfiguration()
+            content.text = item.title
+            content.secondaryText = item.subtitle
+            cell.contentConfiguration = content
+        }
+        
+        dataSource = UICollectionViewDiffableDataSource(collectionView: collectionView) { 
+            collectionView, indexPath, item in
+            collectionView.dequeueConfiguredReusableCell(
+                using: cellRegistration, for: indexPath, item: item
+            )
+        }
+    }
+    
+    func updateItems(_ items: [Item]) {
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        snapshot.appendSections([.main])
+        snapshot.appendItems(items)
+        dataSource.apply(snapshot)
+    }
+}
+```
+
+## Grid Layout
+
+```swift
+private func createGridLayout() -> UICollectionViewLayout {
+    let itemSize = NSCollectionLayoutSize(
+        widthDimension: .fractionalWidth(1/3),
+        heightDimension: .fractionalHeight(1.0)
+    )
+    let item = NSCollectionLayoutItem(layoutSize: itemSize)
+    item.contentInsets = NSDirectionalEdgeInsets(top: 2, leading: 2, bottom: 2, trailing: 2)
+    
+    let groupSize = NSCollectionLayoutSize(
+        widthDimension: .fractionalWidth(1.0),
+        heightDimension: .fractionalWidth(1/3)
+    )
+    let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])
+    
+    let section = NSCollectionLayoutSection(group: group)
+    return UICollectionViewCompositionalLayout(section: section)
+}
+```
+
+## Sectioned List with Headers
+
+```swift
+class CategorizedListVC: UIViewController {
+    enum Section: Hashable {
+        case favorites, recent, all
+    }
+    
+    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
+    
+    private func setupCollectionView() {
+        var config = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
+        config.headerMode = .supplementary
+        
+        let layout = UICollectionViewCompositionalLayout.list(using: config)
+        collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
+    }
+    
+    private func configureDataSource() {
+        let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, Item> { 
+            cell, indexPath, item in
+            var content = cell.defaultContentConfiguration()
+            content.text = item.title
+            cell.contentConfiguration = content
+        }
+        
+        let headerRegistration = UICollectionView.SupplementaryRegistration<UICollectionViewListCell>(
+            elementKind: UICollectionView.elementKindSectionHeader
+        ) { [weak self] header, elementKind, indexPath in
+            guard let section = self?.dataSource.sectionIdentifier(for: indexPath.section) else { return }
+            var content = header.defaultContentConfiguration()
+            content.text = self?.title(for: section)
+            header.contentConfiguration = content
+        }
+        
+        dataSource = UICollectionViewDiffableDataSource(collectionView: collectionView) { 
+            collectionView, indexPath, item in
+            collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: item)
+        }
+        
+        dataSource.supplementaryViewProvider = { collectionView, kind, indexPath in
+            collectionView.dequeueConfiguredReusableSupplementary(using: headerRegistration, for: indexPath)
+        }
+    }
+    
+    func applySnapshot(favorites: [Item], recent: [Item], all: [Item]) {
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        if !favorites.isEmpty {
+            snapshot.appendSections([.favorites])
+            snapshot.appendItems(favorites, toSection: .favorites)
+        }
+        if !recent.isEmpty {
+            snapshot.appendSections([.recent])
+            snapshot.appendItems(recent, toSection: .recent)
+        }
+        snapshot.appendSections([.all])
+        snapshot.appendItems(all, toSection: .all)
+        dataSource.apply(snapshot)
+    }
+}
+```
+
+## Spacing Guidelines
+
+| Spacing | Usage |
+|---------|-------|
+| 8pt | Compact element spacing |
+| 16pt | Standard padding |
+| 24pt | Section spacing |
+| 32pt | Large section separation |
+| 48pt | Screen margins (large screens) |
+
+---
+
+*UIKit and Apple are trademarks of Apple Inc. SnapKit is a trademark of its respective owners.*