ehmo/platform-design-skills/platform-design-skills-2

iOS Design Guidelines for iPhone

Comprehensive rules derived from Apple's Human Interface Guidelines. Apply these when building, reviewing, or refactoring any iPhone app interface.

1. Layout & Safe Areas

Impact: CRITICAL

Rule 1.1: Minimum 44pt Touch Targets

All interactive elements must have a minimum tap target of 44x44 points. This includes buttons, links, toggles, and custom controls.

Correct:

Button("Save") { save() }
    .frame(minWidth: 44, minHeight: 44)

Incorrect:

// 20pt icon with no padding — too small to tap reliably
Button(action: save) {
    Image(systemName: "checkmark")
        .font(.system(size: 20))
}
// Missing .frame(minWidth: 44, minHeight: 44)

Rule 1.2: Respect Safe Areas

Never place interactive or essential content under the status bar, Dynamic Island, or home indicator. Use SwiftUI's automatic safe area handling or UIKit's safeAreaLayoutGuide.

Correct:

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Content")
        }
        // SwiftUI respects safe areas by default
    }
}

Incorrect:

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Content")
        }
        .ignoresSafeArea() // Content will be clipped under notch/Dynamic Island
    }
}

Use .ignoresSafeArea() only for background fills, images, or decorative elements — never for text or interactive controls.

Rule 1.3: Primary Actions in the Thumb Zone

Place primary actions at the bottom of the screen where the user's thumb naturally rests. Secondary actions and navigation belong at the top.

Correct:

VStack {
    ScrollView { /* content */ }
    Button("Continue") { next() }
        .buttonStyle(.borderedProminent)
        .padding()
}

Incorrect:

VStack {
    Button("Continue") { next() } // Top of screen — hard to reach one-handed
        .buttonStyle(.borderedProminent)
        .padding()
    ScrollView { /* content */ }
}

Rule 1.4: Support All iPhone Screen Sizes

Design for iPhone SE (375pt wide) through iPhone Pro Max (430pt wide). Use flexible layouts, avoid hardcoded widths.

Correct:

HStack(spacing: 12) {
    ForEach(items) { item in
        CardView(item: item)
            .frame(maxWidth: .infinity) // Adapts to screen width
    }
}

Incorrect:

HStack(spacing: 12) {
    ForEach(items) { item in
        CardView(item: item)
            .frame(width: 180) // Breaks on SE, wastes space on Pro Max
    }
}

Rule 1.5: 8pt Grid Alignment

Align spacing, padding, and element sizes to multiples of 8 points (8, 16, 24, 32, 40, 48). Use 4pt for fine adjustments.

Rule 1.6: Landscape Support

Support landscape orientation unless the app is task-specific (e.g., camera). Use ViewThatFits or GeometryReader for adaptive layouts.

2. Navigation

Impact: CRITICAL

Rule 2.1: Tab Bar for Top-Level Sections

Use a tab bar at the bottom of the screen for 3 to 5 top-level sections. Each tab should represent a distinct category of content or functionality.

Correct:

TabView {
    HomeView()
        .tabItem {
            Label("Home", systemImage: "house")
        }
    SearchView()
        .tabItem {
            Label("Search", systemImage: "magnifyingglass")
        }
    ProfileView()
        .tabItem {
            Label("Profile", systemImage: "person")
        }
}

Incorrect:

// Hamburger menu hidden behind three lines — discoverability is near zero
NavigationView {
    Button(action: { showMenu.toggle() }) {
        Image(systemName: "line.horizontal.3")
    }
}

Rule 2.2: Never Use Hamburger Menus

Hamburger (drawer) menus hide navigation, reduce discoverability, and violate iOS conventions. Use a tab bar instead. If you have more than 5 sections, consolidate or use a "More" tab.

Rule 2.3: Large Titles in Primary Views

Use .navigationBarTitleDisplayMode(.large) for top-level views. Titles transition to inline (.inline) when the user scrolls.

Correct:

NavigationStack {
    List(items) { item in
        ItemRow(item: item)
    }
    .navigationTitle("Messages")
    .navigationBarTitleDisplayMode(.large)
}

Rule 2.4: Never Override Back Swipe

The swipe-from-left-edge gesture for back navigation is a system-level expectation. Never attach custom gesture recognizers that interfere with it.

Incorrect:

.gesture(
    DragGesture()
        .onChanged { /* custom drawer */ } // Conflicts with system back swipe
)

Rule 2.5: Use NavigationStack for Hierarchical Content

Use NavigationStack (not the deprecated NavigationView) for drill-down content. Use NavigationPath for programmatic navigation.

Correct:

NavigationStack(path: $path) {
    List(items) { item in
        NavigationLink(value: item) {
            ItemRow(item: item)
        }
    }
    .navigationDestination(for: Item.self) { item in
        ItemDetail(item: item)
    }
}

Rule 2.6: Preserve State Across Navigation

When users navigate back and then forward, or switch tabs, restore the previous scroll position and input state. Use @SceneStorage or @State to persist view state.

Rule 2.7: Prefer Recognition Over Recall

Keep current location, recent choices, and available destinations visible. Restore tab, scroll, filter, and selection state so users continue from recognition instead of reconstructing context from memory.

3. Typography & Dynamic Type

Impact: HIGH

Rule 3.1: Use Built-in Text Styles

Always use semantic text styles rather than hardcoded sizes. These scale automatically with Dynamic Type.

Correct:

VStack(alignment: .leading, spacing: 4) {
    Text("Section Title")
        .font(.headline)
    Text("Body content that explains the section.")
        .font(.body)
    Text("Last updated 2 hours ago")
        .font(.caption)
        .foregroundStyle(.secondary)
}

Incorrect:

VStack(alignment: .leading, spacing: 4) {
    Text("Section Title")
        .font(.system(size: 17, weight: .semibold)) // Won't scale with Dynamic Type
    Text("Body content")
        .font(.system(size: 15)) // Won't scale with Dynamic Type
}

Rule 3.2: Support Dynamic Type Including Accessibility Sizes

Dynamic Type can scale text up to approximately 200% at the largest accessibility sizes. Layouts must reflow — never truncate or clip essential text.

Correct:

HStack {
    Image(systemName: "star")
    Text("Favorites")
        .font(.body)
}
// At accessibility sizes, consider using ViewThatFits or
// AnyLayout to switch from HStack to VStack

Use @Environment(\.dynamicTypeSize) to detect size category and adapt layouts:

@Environment(\.dynamicTypeSize) var dynamicTypeSize
 
var body: some View {
    if dynamicTypeSize.isAccessibilitySize {
        VStack { content }
    } else {
        HStack { content }
    }
}

Rule 3.3: Custom Fonts Must Scale with Dynamic Type

If you use a custom typeface, scale it so it responds to Dynamic Type. The API differs by framework.

Correct (SwiftUI):

extension Font {
    static func scaledCustom(size: CGFloat, relativeTo textStyle: Font.TextStyle) -> Font {
        .custom("CustomFont-Regular", size: size, relativeTo: textStyle)
    }
}
 
// Usage
Text("Hello")
    .font(.scaledCustom(size: 17, relativeTo: .body))

Correct (UIKit):

let metrics = UIFontMetrics(forTextStyle: .body)
let customFont = UIFont(name: "CustomFont-Regular", size: 17)!
label.font = metrics.scaledFont(for: customFont)
label.adjustsFontForContentSizeCategory = true

Rule 3.4: SF Pro as System Font

Use the system font (SF Pro) unless brand requirements dictate otherwise. SF Pro is optimized for legibility on Apple displays.

Rule 3.5: Minimum 11pt Text

Never display text smaller than 11pt. Prefer 17pt for body text. Use the caption2 style (11pt) as the absolute minimum.

Rule 3.6: Hierarchy Through Weight and Size

Establish visual hierarchy through font weight and size. Do not rely solely on color to differentiate text levels.

4. Color & Dark Mode

Impact: HIGH

Rule 4.1: Use Semantic System Colors

Use system-provided semantic colors that automatically adapt to light and dark modes.

Correct:

Text("Primary text")
    .foregroundStyle(.primary) // Adapts to light/dark
 
Text("Secondary info")
    .foregroundStyle(.secondary)
 
VStack { }
    .background(Color(.systemBackground)) // White in light, black in dark

Incorrect:

Text("Primary text")
    .foregroundColor(.black) // Invisible on dark backgrounds
 
VStack { }
    .background(.white) // Blinding in Dark Mode

Rule 4.2: Provide Light and Dark Variants for Custom Colors

Define custom colors in the asset catalog with both Any Appearance and Dark Appearance variants.

// In Assets.xcassets, define "BrandBlue" with:
// Any Appearance: #0066CC
// Dark Appearance: #4DA3FF
 
Text("Brand text")
    .foregroundStyle(Color("BrandBlue")) // Automatically switches

Rule 4.3: Never Rely on Color Alone

Always pair color with text, icons, or shapes to convey meaning. Approximately 8% of men have some form of color vision deficiency.

Correct:

HStack {
    Image(systemName: "exclamationmark.triangle.fill")
        .foregroundStyle(.red)
    Text("Error: Invalid email address")
        .foregroundStyle(.red)
}

Incorrect:

// Only color indicates the error — invisible to colorblind users
TextField("Email", text: $email)
    .border(isValid ? .green : .red)

Rule 4.4: 4.5:1 Contrast Ratio Minimum

All text must meet WCAG AA contrast ratios: 4.5:1 for normal text, 3:1 for large text (18pt+ or 14pt+ bold).

Rule 4.5: Support Display P3 Wide Gamut

Use Display P3 color space for vibrant, accurate colors on modern iPhones. Define colors in the asset catalog with the Display P3 gamut.

Rule 4.6: Background Hierarchy

Use the three-level background hierarchy for depth:

• systemBackground — primary surface
• secondarySystemBackground — grouped content, cards
• tertiarySystemBackground — elements within grouped content

Rule 4.7: One Accent Color for Interactive Elements

Choose a single tint/accent color for all interactive elements (buttons, links, toggles). This creates a consistent, learnable visual language.

@main
struct MyApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
                .tint(.indigo) // All interactive elements use indigo
        }
    }
}

5. Accessibility

Impact: CRITICAL

Rule 5.1: VoiceOver Labels on All Interactive Elements

Every button, control, and interactive element must have a meaningful accessibility label.

Correct:

Button(action: addToCart) {
    Image(systemName: "cart.badge.plus")
}
.accessibilityLabel("Add to cart")

Incorrect:

Button(action: addToCart) {
    Image(systemName: "cart.badge.plus")
}
// VoiceOver reads "cart.badge.plus" — meaningless to users

Rule 5.2: Logical VoiceOver Navigation Order

Ensure VoiceOver reads elements in a logical order. Use .accessibilitySortPriority() to adjust when the visual layout doesn't match the reading order.

VStack {
    Text("Price: $29.99")
        .accessibilitySortPriority(1) // Read second (lower number = lower priority)
    Text("Product Name")
        .accessibilitySortPriority(2) // Read first (higher number = higher priority)
}