mobile-ios-design

Imported from wshobson/agents (plugins/ui-design/skills/mobile-ios-design/SKILL.md) via skills.sh. Install upstream with npx skills add wshobson/agents --skill mobile-ios-design. Copyright stays with the author.

iOS Mobile Design

Master iOS Human Interface Guidelines (HIG) and SwiftUI patterns to build polished, native iOS applications that feel at home on Apple platforms.

When to Use This Skill

• Designing iOS app interfaces following Apple HIG
• Building SwiftUI views and layouts
• Implementing iOS navigation patterns (NavigationStack, TabView, sheets)
• Creating adaptive layouts for iPhone and iPad
• Using SF Symbols and system typography
• Building accessible iOS interfaces
• Implementing iOS-specific gestures and interactions
• Designing for Dynamic Type and Dark Mode

Core Concepts

1. Human Interface Guidelines Principles

Clarity: Content is legible, icons are precise, adornments are subtle Deference: UI helps users understand content without competing with it Depth: Visual layers and motion convey hierarchy and enable navigation

Platform Considerations:

• iOS: Touch-first, compact displays, portrait orientation
• iPadOS: Larger canvas, multitasking, pointer support
• visionOS: Spatial computing, eye/hand input

2. SwiftUI Layout System

Stack-Based Layouts:

// Vertical stack with alignment
VStack(alignment: .leading, spacing: 12) {
    Text("Title")
        .font(.headline)
    Text("Subtitle")
        .font(.subheadline)
        .foregroundStyle(.secondary)
}

// Horizontal stack with flexible spacing
HStack {
    Image(systemName: "star.fill")
    Text("Featured")
    Spacer()
    Text("View All")
        .foregroundStyle(.blue)
}

Grid Layouts:

// Adaptive grid that fills available width
LazyVGrid(columns: [
    GridItem(.adaptive(minimum: 150, maximum: 200))
], spacing: 16) {
    ForEach(items) { item in
        ItemCard(item: item)
    }
}

// Fixed column grid
LazyVGrid(columns: [
    GridItem(.flexible()),
    GridItem(.flexible()),
    GridItem(.flexible())
], spacing: 12) {
    ForEach(items) { item in
        ItemThumbnail(item: item)
    }
}

3. Navigation Patterns

NavigationStack (iOS 16+):

struct ContentView: View {
    @State private var path = NavigationPath()

    var body: some View {
        NavigationStack(path: $path) {
            List(items) { item in
                NavigationLink(value: item) {
                    ItemRow(item: item)
                }
            }
            .navigationTitle("Items")
            .navigationDestination(for: Item.self) { item in
                ItemDetailView(item: item)
            }
        }
    }
}

TabView (iOS 18+):

struct MainTabView: View {
    @State private var selectedTab = 0

    var body: some View {
        TabView(selection: $selectedTab) {
            Tab("Home", systemImage: "house", value: 0) {
                HomeView()
            }

            Tab("Search", systemImage: "magnifyingglass", value: 1) {
                SearchView()
            }

            Tab("Profile", systemImage: "person", value: 2) {
                ProfileView()
            }
        }
    }
}

4. System Integration

SF Symbols:

// Basic symbol
Image(systemName: "heart.fill")
    .foregroundStyle(.red)

// Symbol with rendering mode
Image(systemName: "cloud.sun.fill")
    .symbolRenderingMode(.multicolor)

// Variable symbol (iOS 16+)
Image(systemName: "speaker.wave.3.fill", variableValue: volume)

// Symbol effect (iOS 17+)
Image(systemName: "bell.fill")
    .symbolEffect(.bounce, value: notificationCount)

Dynamic Type:

// Use semantic fonts
Text("Headline")
    .font(.headline)

Text("Body text that scales with user preferences")
    .font(.body)

// Custom font that respects Dynamic Type
Text("Custom")
    .font(.custom("Avenir", size: 17, relativeTo: .body))

5. Visual Design

Colors and Materials:

// Semantic colors that adapt to light/dark mode
Text("Primary")
    .foregroundStyle(.primary)
Text("Secondary")
    .foregroundStyle(.secondary)

// System materials for blur effects
Rectangle()
    .fill(.ultraThinMaterial)
    .frame(height: 100)

// Vibrant materials for overlays
Text("Overlay")
    .padding()
    .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 12))

Shadows and Depth:

// Standard card shadow
RoundedRectangle(cornerRadius: 16)
    .fill(.background)
    .shadow(color: .black.opacity(0.1), radius: 8, y: 4)

// Elevated appearance
.shadow(radius: 2, y: 1)
.shadow(radius: 8, y: 4)

Quick Start Component

import SwiftUI

struct FeatureCard: View {
    let title: String
    let description: String
    let systemImage: String

    var body: some View {
        HStack(spacing: 16) {
            Image(systemName: systemImage)
                .font(.title)
                .foregroundStyle(.blue)
                .frame(width: 44, height: 44)
                .background(.blue.opacity(0.1), in: Circle())

            VStack(alignment: .leading, spacing: 4) {
                Text(title)
                    .font(.headline)
                Text(description)
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                    .lineLimit(2)
            }

            Spacer()

            Image(systemName: "chevron.right")
                .foregroundStyle(.tertiary)
        }
        .padding()
        .background(.background, in: RoundedRectangle(cornerRadius: 12))
        .shadow(color: .black.opacity(0.05), radius: 4, y: 2)
    }
}

Best Practices

1. Use Semantic Colors: Always use .primary, .secondary, .background for automatic light/dark mode support
2. Embrace SF Symbols: Use system symbols for consistency and automatic accessibility
3. Support Dynamic Type: Use semantic fonts (.body, .headline) instead of fixed sizes
4. Add Accessibility: Include .accessibilityLabel() and .accessibilityHint() modifiers
5. Use Safe Areas: Respect safeAreaInset and avoid hardcoded padding at screen edges
6. Implement State Restoration: Use @SceneStorage for preserving user state
7. Support iPad Multitasking: Design for split view and slide over
8. Test on Device: Simulator doesn't capture full haptic and performance experience

Common Issues

• Layout Breaking: Use .fixedSize() sparingly; prefer flexible layouts
• Performance Issues: Use LazyVStack/LazyHStack for long scrolling lists
• Navigation Bugs: Ensure NavigationLink values are Hashable
• Dark Mode Problems: Avoid hardcoded colors; use semantic or asset catalog colors
• Accessibility Failures: Test with VoiceOver enabled
• Memory Leaks: Watch for strong reference cycles in closures