swiftui-development

name	swiftui-development
description	Master SwiftUI - Declarative UI, state management, animations, modern iOS development
sasmp_version	1.3.0
version	2.0.0
bonded_agent	03-swiftui-development
bond_type	PRIMARY_BOND
last_updated	2024-12

SwiftUI Development Skill

Build modern, declarative iOS interfaces with SwiftUI

Learning Objectives

By completing this skill, you will:

• Create declarative UIs with SwiftUI views
• Master state management (@State, @Binding, @Observable)
• Implement complex navigation with NavigationStack
• Create fluid animations and transitions
• Build production-ready SwiftUI applications

Prerequisites

Requirement	Level
iOS Fundamentals	Completed
Swift	Intermediate
Functional programming concepts	Basic

Curriculum

Module 1: SwiftUI Fundamentals (4 hours)

Topics:

• View protocol and body
• ViewBuilder and composition
• Modifiers and their order
• @ViewBuilder for custom containers
• Environment and preferences

Code Examples:

// Basic view composition
struct ProfileView: View {
    let user: User

    var body: some View {
        VStack(spacing: 16) {
            ProfileImage(url: user.avatarURL)

            Text(user.name)
                .font(.title)
                .fontWeight(.bold)

            Text(user.bio)
                .font(.body)
                .foregroundStyle(.secondary)
                .multilineTextAlignment(.center)
        }
        .padding()
    }
}

// Custom container with ViewBuilder
struct Card<Content: View>: View {
    let content: Content

    init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }

    var body: some View {
        content
            .padding()
            .background(.background)
            .clipShape(RoundedRectangle(cornerRadius: 12))
            .shadow(radius: 4)
    }
}

Checkpoint: Build profile card component

---

Module 2: State Management (6 hours)

Topics:

• @State for local state
• @Binding for two-way binding
• @StateObject vs @ObservedObject
• @EnvironmentObject for shared state
• @Observable (iOS 17+)
• Combine integration

State Hierarchy:

@State → Local, value type
@Binding → Pass to child, two-way
@StateObject → Own the object, create once
@ObservedObject → Don't own, receive from parent
@EnvironmentObject → Shared globally
@Observable → Modern replacement (iOS 17+)

Modern Approach (iOS 17+):

@Observable
final class UserViewModel {
    var user: User?
    var isLoading = false
    var error: Error?

    private let service: UserServiceProtocol

    init(service: UserServiceProtocol = UserService()) {
        self.service = service
    }

    func loadUser() async {
        isLoading = true
        defer { isLoading = false }

        do {
            user = try await service.fetchCurrentUser()
        } catch {
            self.error = error
        }
    }
}

struct UserView: View {
    @State private var viewModel = UserViewModel()

    var body: some View {
        Group {
            if viewModel.isLoading {
                ProgressView()
            } else if  user  viewModel.user {
                (user: user)
            }
        }
        .task {
             viewModel.loadUser()
        }
    }
}

Checkpoint: Build stateful form with validation

---

Module 3: Navigation (5 hours)

Topics:

• NavigationStack (iOS 16+)
• NavigationPath for programmatic navigation
• NavigationSplitView for iPad
• Sheet, fullScreenCover, alert
• Deep linking with URL schemes

Navigation Stack:

enum Route: Hashable {
    case profile(userId: String)
    case settings
    case detail(item: Item)
}

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

    var body: some View {
        NavigationStack(path: $path) {
            HomeView(navigate: navigate)
                .navigationDestination(for: Route.self) { route in
                    switch route {
                    case .profile(let userId):
                        ProfileView(userId: userId)
                    case .settings:
                        SettingsView()
                    case .detail(let item):
                        DetailView(item: item)
                    }
                }
        }
    }

    private func navigate(to route: Route) {
        path.append(route)
    }

    private func popToRoot() {
        path.removeLast(path.count)
    }
}

Checkpoint: Build multi-screen navigation flow

---

Module 4: Lists & Grids (4 hours)

Topics:

• List and ForEach
• LazyVStack and LazyVGrid
• Swipe actions and context menus
• Searchable modifier
• Pull-to-refresh

Grid Layout:

struct PhotoGrid: View {
    let photos: [Photo]

    private let columns = [
        GridItem(.adaptive(minimum: 100, maximum: 150), spacing: 8)
    ]

    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns, spacing: 8) {
                ForEach(photos) { photo in
                    AsyncImage(url: photo.thumbnailURL) { phase in
                        switch phase {
                        case .empty:
                            Rectangle()
                                .fill(.quaternary)
                        case .success(let image):
                            image
                                .resizable()
                                .scaledToFill()
                        case .failure:
                            Image(systemName: "photo")
                        @unknown default:
                            EmptyView()
                        }
                    }
                    .frame(height: 100)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                }
            }
            .padding()
        }
    }
}

Checkpoint: Build searchable photo grid

---

Module 5: Animations (4 hours)

Topics:

• Implicit animations (.animation)
• Explicit animations (withAnimation)
• Transitions
• matchedGeometryEffect
• Phase animator (iOS 17+)

Animation Examples:

// Implicit animation
struct ExpandableCard: View {
    @State private var isExpanded = false

    var body: some View {
        VStack {
            Text("Title")
                .font(.headline)

            if isExpanded {
                Text("Detailed content here...")
                    .transition(.opacity.combined(with: .move(edge: .top)))
            }
        }
        .frame(maxWidth: .infinity)
        .padding()
        .background(.background)
        .clipShape(RoundedRectangle(cornerRadius: 12))
        .onTapGesture {
            withAnimation(.spring(response: 0.4, dampingFraction: 0.8)) {
                isExpanded.toggle()
            }
        }
    }
}

// Matched geometry effect
struct CardTransition: View {
    @Namespace private var animation
    @State private var selectedCard: Card?

    var body: some View {
        ZStack {
            if let card = selectedCard {
                DetailView(card: card)
                    .matchedGeometryEffect(id: card.id, in: animation)
                    .onTapGesture { selectedCard = nil }
            }  {
                (columns: columns) {
                    (cards) { card 
                        (card: card)
                            .matchedGeometryEffect(id: card.id, in: animation)
                            .onTapGesture { selectedCard  card }
                    }
                }
            }
        }
        .animation(.spring(response: ), value: selectedCard)
    }
}

Checkpoint: Create hero animation transition

---

Module 6: Custom Modifiers & Styles (3 hours)

Topics:

• ViewModifier protocol
• ButtonStyle, LabelStyle
• Custom environment values
• Preference keys
• View extensions

Custom Modifier:

struct CardStyle: ViewModifier {
    let isHighlighted: Bool

    func body(content: Content) -> some View {
        content
            .padding()
            .background(.background)
            .clipShape(RoundedRectangle(cornerRadius: 12))
            .shadow(
                color: isHighlighted ? .accentColor.opacity(0.3) : .black.opacity(0.1),
                radius: isHighlighted ? 8 : 4
            )
            .overlay {
                if isHighlighted {
                    RoundedRectangle(cornerRadius: 12)
                        .stroke(.accent, lineWidth: 2)
                }
            }
    }
}

extension View {
    func cardStyle(isHighlighted: Bool = false) -> some View {
        modifier(CardStyle(isHighlighted: isHighlighted))
    }
}

// Usage
Text("Content")
    .cardStyle(isHighlighted: true)

Checkpoint: Build custom button style library

---

Assessment Criteria

Criteria	Weight
View composition	25%
State management	30%
Navigation	20%
Animation quality	15%
Code organization	10%

Common Mistakes

1. @StateObject vs @ObservedObject → Use @StateObject for creation
2. ForEach without id → Always use identifiable items
3. Nested NavigationStack → Only one per hierarchy
4. Heavy body computation → Extract to computed properties
5. Missing .animation value → Always specify animation trigger

Debugging Tips

// Debug view updates
var body: some View {
    let _ = Self._printChanges()
    // Your view...
}

// Debug layout
view.border(.red) // Visual bounds

Resources

Official Documentation

• SwiftUI Documentation
• SwiftUI Tutorials
• Human Interface Guidelines

Skill Validation

Complete these projects:

1. Component Library: 10 reusable SwiftUI components
2. Stateful App: Todo app with persistence
3. Navigation Demo: Deep-linkable multi-screen app
4. Animation Showcase: Hero transitions and gestures