ios-application-dev

iOS Application Development Guide A practical guide for building iOS applications using UIKit, SnapKit, and SwiftUI. Focuses on proven patterns and Apple platform conventions. Quick Reference UIKit Purpose Component Main sections UITabBarController Drill-down UINavigationController Focused task Sheet presentation Critical choice UIAlertController Secondary actions UIContextMenuInteraction List content UICollectionView + DiffableDataSource Sectioned list DiffableDataSource + headerMode Grid layout UICollectionViewCompositionalLayout Search UISearchController Share UIActivityViewController Location (once) CLLocationButton Feedback UIImpactFeedbackGenerator Linear layout UIStackView Custom shapes CAShapeLayer + UIBezierPath Gradients CAGradientLayer Modern buttons UIButton.Configuration Dynamic text UIFontMetrics + preferredFont Dark mode Semantic colors ( .systemBackground , .label ) Permissions Contextual request + AVCaptureDevice Lifecycle UIApplication notifications SwiftUI Purpose Component Main sections TabView + tabItem Drill-down NavigationStack + NavigationPath Focused task .sheet + presentationDetents Critical choice .alert Secondary actions .contextMenu List content List + .insetGrouped Search .searchable Share ShareLink Location (once) LocationButton Feedback UIImpactFeedbackGenerator Progress (known) ProgressView(value:total:) Progress (unknown) ProgressView() Dynamic text .font(.body) semantic styles Dark mode .primary , .secondary , Color(.systemBackground) Scene lifecycle @Environment(.scenePhase) Reduce motion @Environment(.accessibilityReduceMotion) Dynamic type @Environment(.dynamicTypeSize) Core Principles Layout Touch targets >= 44pt Content within safe areas (SwiftUI respects by default, use .ignoresSafeArea() only for backgrounds) Use 8pt spacing increments (8, 16, 24, 32, 40, 48) Primary actions in thumb zone Support all screen sizes (iPhone SE 375pt to Pro Max 430pt) Typography UIKit: preferredFont(forTextStyle:) + adjustsFontForContentSizeCategory = true SwiftUI: semantic text styles .headline , .body , .caption Custom fonts: UIFontMetrics / Font.custom(_:size:relativeTo:) Adapt layout at accessibility sizes (minimum 11pt) Colors Use semantic system colors ( .systemBackground , .label , .primary , .secondary ) Asset catalog variants for custom colors (Any/Dark Appearance) No color-only information (pair with icons or text) Contrast ratio >= 4.5:1 for normal text, 3:1 for large text Accessibility Labels on icon buttons ( .accessibilityLabel() ) Reduce motion respected ( @Environment(.accessibilityReduceMotion) ) Logical reading order ( .accessibilitySortPriority() ) Support Bold Text, Increase Contrast preferences Navigation Tab bar (3-5 sections) stays visible during navigation Back swipe works (never override system gestures) State preserved across tabs ( @SceneStorage , @State ) Never use hamburger menus Privacy & Permissions Request permissions in context (not at launch) Custom explanation before system dialog Support Sign in with Apple Respect ATT denial Checklist Layout Touch targets >= 44pt Content within safe areas Primary actions in thumb zone (bottom half) Flexible widths for all screen sizes (SE to Pro Max) Spacing aligns to 8pt grid Typography Semantic text styles or UIFontMetrics-scaled custom fonts Dynamic Type supported up to accessibility sizes Layouts reflow at large sizes (no truncation) Minimum text size 11pt Colors Semantic system colors or light/dark asset variants Dark Mode is intentional (not just inverted) No color-only information Text contrast >= 4.5:1 (normal) / 3:1 (large) Single accent color for interactive elements Accessibility VoiceOver labels on all interactive elements Logical reading order Bold Text preference respected Reduce Motion disables decorative animations All gestures have alternative access paths Navigation Tab bar for 3-5 top-level sections No hamburger/drawer menus Tab bar stays visible during navigation Back swipe works throughout State preserved across tabs Components Alerts for critical decisions only Sheets have dismiss path (button and/or swipe) List rows >= 44pt tall Destructive buttons use .destructive role Privacy Permissions requested in context (not at launch) Custom explanation before system permission dialog Sign in with Apple offered with other providers Basic features usable without account ATT prompt shown if tracking, denial respected System Integration App handles interruptions gracefully (calls, background, Siri) App content indexed for Spotlight Share Sheet available for shareable content References Topic Reference Touch Targets, Safe Area, CollectionView Layout System TabBar, NavigationController, Modal Navigation Patterns StackView, Button, Alert, Search, ContextMenu UIKit Components CAShapeLayer, CAGradientLayer, Core Animation Graphics & Animation Dynamic Type, Semantic Colors, VoiceOver Accessibility Permissions, Location, Share, Lifecycle, Haptics System Integration Metal Shaders & GPU Metal Shader Reference SwiftUI HIG, Components, Patterns, Anti-Patterns SwiftUI Design Guidelines Optionals, Protocols, async/await, ARC, Error Handling Swift Coding Standards Swift, SwiftUI, UIKit, SF Symbols, Metal, and Apple are trademarks of Apple Inc. SnapKit is a trademark of its respective owners.