iOS Design Skill

Expert knowledge of Apple Human Interface Guidelines for SwiftUI applications. This skill enforces design excellence, accessibility compliance, and iOS-native feel.

Core Principles

1. iOS Native Feel

• Use system colors and semantic tokens
• Follow Dynamic Type for text scaling
• Respect Safe Areas and notches
• Support both light and dark mode

2. Accessibility First

• Minimum 44x44pt touch targets
• 4.5:1 contrast ratio for normal text
• Proper accessibilityLabel on all interactive elements
• Support Dynamic Type up to AX5 (largest accessibility sizes)

3. SwiftUI Best Practices

• Use correct property wrappers (@State, @StateObject, @ObservedObject)
• Prefer declarative patterns
• Avoid AnyView type erasure
• Provide stable IDs in ForEach

---

Typography Scale (11 Styles)

Style	Size (Default)	Weight	Use Case
.largeTitle	34pt	Regular	Hero headlines
.title	28pt	Regular	Page titles
.title2	22pt	Regular	Section headers
.title3	20pt	Regular	Subsection headers
.headline	17pt	Semibold	Emphasized body
.body	17pt	Regular	Main content
.callout	16pt	Regular	Secondary content
.subheadline	15pt	Regular	Supporting text
.footnote	13pt	Regular	Metadata
.caption	12pt	Regular	Captions
.caption2	11pt	Regular	Small labels

Usage Pattern

// GOOD - System text styles
Text("Welcome")
    .font(.largeTitle)

// BAD - Hardcoded sizes
Text("Welcome")
    .font(.system(size: 34))

Dynamic Type Support

// Automatic scaling with system styles
Text("Body text")
    .font(.body)

// Custom sizes that scale
@ScaledMetric(relativeTo: .body) var iconSize: CGFloat = 24

Image(systemName: "star.fill")
    .frame(width: iconSize, height: iconSize)

---

Color System

Semantic Colors

Token	Light	Dark	Use Case
.label	Black	White	Primary text
.secondaryLabel	Gray	Light gray	Secondary text
.tertiaryLabel	Light gray	Darker gray	Tertiary text
.quaternaryLabel	Lighter gray	Darkest gray	Disabled text
.systemBackground	White	Black	Primary background
.secondarySystemBackground	Light gray	Dark gray	Grouped content
.tertiarySystemBackground	White	Darker gray	Elevated content
.separator	Light gray	Dark gray	Dividers
.link	System blue	System blue	Interactive links

System Colors

Color	Use Case
.accentColor	Primary interactive elements
.red	Destructive actions, errors
.orange	Warnings
.yellow	Caution
.green	Success, positive
.blue	Default interactive
.purple	Special features
.pink	Playful accents

Usage Pattern

// GOOD - Semantic colors
Text("Primary content")
    .foregroundColor(.label)

VStack {
    // content
}
.background(Color(.systemBackground))

// BAD - Hardcoded colors
Text("Primary content")
    .foregroundColor(.black)

VStack {
    // content
}
.background(Color.white)

---

Touch Targets

Requirements

• Minimum: 44x44pt (Apple HIG requirement)
• Bottom navigation: 46-50pt recommended
• Spacing: 8pt minimum between targets

Implementation

// GOOD - System button provides proper touch target
Button(action: { /* action */ }) {
    Image(systemName: "xmark")
}

// GOOD - Custom with proper frame
Image(systemName: "xmark")
    .frame(width: 44, height: 44)
    .contentShape(Rectangle())
    .onTapGesture { /* action */ }

// BAD - Too small
Image(systemName: "xmark")
    .font(.system(size: 16))
    .onTapGesture { /* action */ }

---

Safe Areas

Respecting Safe Areas

// GOOD - Content respects safe areas
ScrollView {
    content
}
.safeAreaInset(edge: .bottom) {
    bottomBar
}

// Full-bleed backgrounds that extend into safe areas
ZStack {
    Color.blue.ignoresSafeArea()

    VStack {
        content // Content still respects safe areas
    }
}

Device-Specific Considerations

Device	Top Safe Area	Bottom Safe Area
iPhone (notch)	47pt	34pt
iPhone (Dynamic Island)	59pt	34pt
iPhone SE	20pt	0pt
iPad	20pt	0pt

---

Spacing Scale

Base unit: 4pt

Size	pt	Use Case
xs	4pt	Inline spacing
sm	8pt	Related elements
md	12pt	Group spacing
lg	16pt	Section spacing
xl	20pt	Major divisions
2xl	24pt	Page margins (compact)
3xl	32pt	Large gaps

Standard Margins

Context	Margin
Compact width	16pt
Regular width	20pt
List insets	16pt leading, 20pt trailing

---

DO / DON'T

Property Wrappers

DO: Use @StateObject for owned objects

struct ContentView: View {
    @StateObject private var viewModel = ContentViewModel()

    var body: some View {
        Text(viewModel.text)
    }
}

DON'T: Use @ObservedObject for owned objects

struct ContentView: View {
    @ObservedObject var viewModel = ContentViewModel() // Re-created on every view update!

    var body: some View {
        Text(viewModel.text)
    }
}

List Performance

DO: Use LazyVStack/List for long content

ScrollView {
    LazyVStack {
        ForEach(items, id: \.id) { item in
            ItemRow(item: item)
        }
    }
}

DON'T: Use VStack for many items

ScrollView {
    VStack { // All items created at once
        ForEach(items, id: \.id) { item in
            ItemRow(item: item)
        }
    }
}

View Identity

DO: Provide stable IDs in ForEach

ForEach(items, id: \.id) { item in
    ItemRow(item: item)
}

DON'T: Use indices or miss id parameter

ForEach(items.indices, id: \.self) { index in // Breaks on reorder
    ItemRow(item: items[index])
}

Type Erasure

DO: Use @ViewBuilder or concrete types

@ViewBuilder
var content: some View {
    if condition {
        Text("A")
    } else {
        Image(systemName: "star")
    }
}

DON'T: Use AnyView excessively

var content: AnyView { // Kills performance
    if condition {
        return AnyView(Text("A"))
    } else {
        return AnyView(Image(systemName: "star"))
    }
}

Modifier Order

DO: Background before padding, frame before overlay

Text("Hello")
    .padding()
    .background(Color.blue) // Includes padding in background

Text("World")
    .frame(maxWidth: .infinity)
    .overlay(alignment: .trailing) { // Overlay spans full width
        Button("Edit") { }
    }

DON'T: Wrong order causes unexpected results

Text("Hello")
    .background(Color.blue) // Only behind text
    .padding() // Padding outside background

Text("World")
    .overlay(alignment: .trailing) { // Overlay only covers text width
        Button("Edit") { }
    }
    .frame(maxWidth: .infinity)

---

Severity Levels

When auditing, classify issues as:

Level	Icon	Description	Example
Critical	🔴	Blocks accessibility or causes crashes	Missing accessibilityLabel
Important	🟠	Violates HIG or hurts UX	Touch target < 44pt
Warning	🟡	Suboptimal but functional	Hardcoded color
Suggestion	🔵	Polish opportunities	Non-standard spacing

---

Expert References

SwiftUI Architecture & Patterns

• WWDC 2021: Demystify SwiftUI - View identity, lifetime, dependencies
• Property Wrapper Decision Tree - @State, @StateObject, @Observable, @Binding rules + scanner patterns
• IceCubesApp Production Patterns - Real-world patterns from largest open-source SwiftUI app

Modern iOS 18 Features

• iOS 18 Materials & Glass Effects - Material API, glass morphism, liquid glass design

Anti-Patterns & Scanning

• Anti-Patterns Database - 23 patterns with regex scanners for automated audits