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.