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#

PurposeComponentMain sectionsUITabBarControllerDrill-downUINavigationControllerFocused taskSheet presentationCritical choiceUIAlertControllerSecondary actionsUIContextMenuInteractionList contentUICollectionView + DiffableDataSourceSectioned listDiffableDataSource + headerModeGrid layoutUICollectionViewCompositionalLayoutSearchUISearchControllerShareUIActivityViewControllerLocation (once)CLLocationButtonFeedbackUIImpactFeedbackGeneratorLinear layoutUIStackViewCustom shapesCAShapeLayer + UIBezierPathGradientsCAGradientLayerModern buttonsUIButton.ConfigurationDynamic textUIFontMetrics + preferredFontDark modeSemantic colors ( .systemBackground, .label)PermissionsContextual request + AVCaptureDeviceLifecycleUIApplication notifications

SwiftUI#

PurposeComponentMain sectionsTabView + tabItemDrill-downNavigationStack + NavigationPathFocused task.sheet + presentationDetentsCritical choice.alertSecondary actions.contextMenuList contentList + .insetGroupedSearch.searchableShareShareLinkLocation (once)LocationButtonFeedbackUIImpactFeedbackGeneratorProgress (known)ProgressView(value:total:)Progress (unknown)ProgressView()Dynamic text.font(.body) semantic stylesDark 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#

TopicReferenceTouch Targets, Safe Area, CollectionViewLayout SystemTabBar, NavigationController, ModalNavigation PatternsStackView, Button, Alert, Search, ContextMenuUIKit ComponentsCAShapeLayer, CAGradientLayer, Core AnimationGraphics & AnimationDynamic Type, Semantic Colors, VoiceOverAccessibilityPermissions, Location, Share, Lifecycle, HapticsSystem IntegrationMetal Shaders & GPUMetal Shader ReferenceSwiftUI HIG, Components, Patterns, Anti-PatternsSwiftUI Design GuidelinesOptionals, Protocols, async/await, ARC, Error HandlingSwift Coding Standards

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Swift, SwiftUI, UIKit, SF Symbols, Metal, and Apple are trademarks of Apple Inc. SnapKit is a trademark of its respective owners.