Comments: Documentation Waypoints in Your SwiftUI Codebase

/// A custom button that adapts its appearance based on the current context.
/// 
/// This button automatically adjusts its color scheme, haptic feedback,
/// and animation style based on the current device capabilities and user
/// preferences.
///
/// - Parameters:
///   - title: The text to display on the button
///   - action: The closure to execute when the button is tapped
///   - style: The base style of the button (defaults to .primary)
struct AdaptiveButton: View {
    let title: String
    let action: () -> Void
    let style: ButtonStyle

    // Implementation...
}

struct CarouselView: View {
    @State private var activeIndex = 0
    let items: [CarouselItem]

    var body: some View {
        GeometryReader { geometry in
            HStack(spacing: 0) {
                ForEach(0..<items.count, id: \.self) { index in
                    items[index].view
                        .frame(width: geometry.size.width)
                        .offset(x: CGFloat(index - activeIndex) * geometry.size.width)
                        /* 
                         * Apply transformation based on distance from active index:
                         * - Active item (index == activeIndex): No transformation
                         * - Adjacent items: Scaled down to 90% and faded to 70% opacity
                         * - Other items: Scaled down to 80% and faded to 40% opacity
                         * 
                         * Using abs() to handle items both before and after the active item uniformly
                         */
                        .scaleEffect(transformScale(for: index))
                        .opacity(transformOpacity(for: index))
                }
            }
            .animation(.spring(), value: activeIndex)
            // Capture drag gesture to allow manual carousel swiping
            .gesture(DragGesture()
                .onEnded { gesture in
                    /* 
                     * Calculate the new active index based on drag direction and velocity:
                     * - If drag distance > 1/3 of screen width OR velocity is high:
                     *   - Advance in the direction of the drag
                     * - Otherwise:
                     *   - Snap back to the current index
                     */
                    let dragThreshold = geometry.size.width / 3
                    let velocity = gesture.predictedEndLocation.x - gesture.location.x
                    let significantDrag = abs(gesture.translation.width) > dragThreshold
                    let significantVelocity = abs(velocity) > 100
                    let dragToRight = gesture.translation.width > 0

                    if (significantDrag || significantVelocity) && dragToRight && activeIndex > 0 {
                        activeIndex -= 1
                    } else if (significantDrag || significantVelocity) && !dragToRight && activeIndex < items.count - 1 {
                        activeIndex += 1
                    }
                })
        }
    }

    // Helper functions for calculating transformations based on index distance
    private func transformScale(for index: Int) -> CGFloat {
        let distance = abs(index - activeIndex)
        if distance == 0 {
            return 1.0 // Active item at full scale
        } else if distance == 1 {
            return 0.9 // Adjacent items slightly scaled down
        } else {
            return 0.8 // Distant items scaled down further
        }
    }

    private func transformOpacity(for index: Int) -> Double {
        let distance = abs(index - activeIndex)
        if distance == 0 {
            return 1.0 // Active item fully opaque
        } else if distance == 1 {
            return 0.7 // Adjacent items slightly faded
        } else {
            return 0.4 // Distant items more faded
        }
    }
}

struct SubscriptionView: View {
    @StateObject private var viewModel = SubscriptionViewModel()

    var body: some View {
        VStack {
            // Subscription tier selection
            ForEach(viewModel.availableTiers) { tier in
                TierSelectionCard(tier: tier, isSelected: viewModel.selectedTier?.id == tier.id)
                    .onTapGesture {
                        viewModel.selectTier(tier)
                    }
            }

            // Pricing information
            VStack(alignment: .leading) {
                Text(viewModel.formattedPrice)
                    .font(.title2)

                /*
                 * Trial Period Logic:
                 * - New users: 14-day free trial for all tiers
                 * - Returning users upgrading: Pro-rated trial until next billing date
                 * - Returning users downgrading: No trial, changes applied at next billing cycle
                 *
                 * Note: Enterprise tiers never receive a trial period regardless of user status
                 */
                if let trialInfo = viewModel.trialInformation {
                    Text(trialInfo.description)
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                }

                /* 
                 * Promotional Discounts:
                 * - "First 3 months" promotion: Available for new subscribers only
                 * - "Annual plan" discount: 15% off monthly price when billed annually
                 * - "Loyalty" discount: 10% for users who have been subscribers for >12 months
                 *
                 * Discounts are not cumulative; only the highest applicable discount is applied
                 */
                if let discountInfo = viewModel.applicableDiscount {
                    Text(discountInfo.description)
                        .font(.subheadline)
                        .foregroundColor(.green)
                }
            }
            .padding()

            // Purchase button
            Button("Subscribe Now") {
                Task {
                    await viewModel.processPurchase()
                }
            }
            .disabled(!viewModel.canPurchase)
        }
    }
}

struct DashboardScreen: View {
    @StateObject private var viewModel = DashboardViewModel()

    var body: some View {
        NavigationView {
            ScrollView {
                LazyVStack(spacing: 16) {
                    /* Header Section
                     * - User profile summary
                     * - Quick actions
                     * - Notification indicator
                     * 
                     * This section remains visible when scrolling down
                     * and contains frequently accessed user actions
                     */
                    HeaderView(user: viewModel.currentUser)
                        .padding(.horizontal)

                    /* Main Content Cards
                     * Cards are loaded asynchronously based on user's preferences
                     * and are refreshed on pull-to-refresh or when returning to the tab
                     */
                    if viewModel.isLoading {
                        ProgressView()
                    } else {
                        ForEach(viewModel.contentCards) { card in
                            CardView(card: card)
                                .padding(.horizontal)
                        }
                    }

                    /* Activity Feed
                     * - Shows recent activity from connected accounts
                     * - Paginated loading (initial 10 items + load more)
                     * - Pull-to-refresh enabled
                     * 
                     * Note: This section is hidden for free-tier users
                     */
                    if viewModel.userHasActivityAccess {
                        ActivityFeedView(activities: viewModel.recentActivities)
                            .padding(.top)
                    }

                    /* Footer Information
                     * - Support links
                     * - Terms and privacy links
                     * - App version
                     */
                    FooterView()
                        .padding()
                }
            }
            .refreshable {
                await viewModel.refreshData()
            }
            .navigationTitle("Dashboard")
            .toolbar {
                // Toolbar implementation...
            }
        }
    }
}

struct ImageGallery: View {
    @State private var images: [GalleryImage] = []
    @State private var isLoading = false

    var body: some View {
        VStack {
            // TODO: Add pull-to-refresh support once we upgrade to iOS 15+
            ScrollView {
                LazyVGrid(columns: [GridItem(.adaptive(minimum: 120))]) {
                    ForEach(images) { image in
                        GalleryThumbnail(image: image)
                            // FIXME: Image caching isn't working properly on slow networks
                            .onAppear {
                                if image.id == images.last?.id && !isLoading {
                                    loadMoreImages()
                                }
                            }
                    }
                }
                .padding()
            }

            // WARNING: This button will be removed in v2.0 when we implement automatic loading
            Button("Load More") {
                loadMoreImages()
            }
            .disabled(isLoading)
        }
        .task {
            if images.isEmpty {
                await loadInitialImages()
            }
        }
    }

    private func loadInitialImages() async {
        // Implementation...
    }

    private func loadMoreImages() {
        // Implementation...
    }
}

// Poor comment - states the obvious
Button("Save") { // This creates a button
    saveData()
}

// Better comment - explains intent or non-obvious behavior
Button("Save") { // Uses haptic feedback and shows saving indicator
    HapticFeedback.success()
    viewModel.isSaving = true
    Task {
        await saveData()
        viewModel.isSaving = false
    }
}

// Too terse - missing important context
// Special case
if user.subscription == .premium && daysSinceLastLogin > 30 {
    showWelcomeBackOffer = true
}

// Too verbose - drowns important information in words
// If the user is a premium subscriber, which means they have paid for our premium tier service
// that gives them access to all the premium features, and they haven't logged in for more than
// 30 days, which we track using the lastLoginDate property and calculating the difference from 
// today's date, then we will show them a special welcome back offer to encourage re-engagement
// with the application and to reward their loyalty as a premium subscriber.
if user.subscription == .premium && daysSinceLastLogin > 30 {
    showWelcomeBackOffer = true
}

// Just right - explains the rationale concisely
// Show re-engagement offer to premium subscribers who have been inactive for >30 days
if user.subscription == .premium && daysSinceLastLogin > 30 {
    showWelcomeBackOffer = true
}

// Original code with accurate comment
// Apply discount only for orders above $100
if cart.total > 100 {
    cart.applyDiscount(0.1) // 10% discount
}

// Later modification with outdated comment
// Apply discount only for orders above $100
if cart.total > 75 { // Changed threshold but didn't update comment
    cart.applyDiscount(0.15) // Changed to 15% but didn't update comment
}

// Updated comment that matches the current implementation
// Apply 15% discount for orders above $75
if cart.total > 75 {
    cart.applyDiscount(0.15)
}

// Redundant comments that add no value
var username: String // The username
var isLoggedIn = false // Boolean to track if user is logged in

// Setting the background color to blue
background(.blue)

// Loop through each item in the array
for item in items {
    // ...
}

// Valuable comments that explain reasoning or constraints
// Using force unwrap here because this view is only accessible after authentication
let user = userManager.currentUser!

// Half-point border improves sharpness on non-Retina displays
.border(Color.gray, width: 0.5)

// Using lazy loading to improve initial render performance
LazyVStack {
    // ...
}

// Comment focused on "what" (less useful)
// Set the corner radius to 8 points
.cornerRadius(8)

// Comment focused on "why" (more useful)
// Matching corner radius with system cards for visual consistency
.cornerRadius(8)

// Another example of explaining "why"
// Using custom tap gesture instead of Button to prevent highlight state on iPad
.onTapGesture {
    handleTap()
}

// Explaining a workaround or limitation
// Force unwrapping here because SwiftUI's environment initializes after body is first evaluated
// This is safe because we've confirmed the environment value will be set before any user interaction
let theme = themeManager.currentTheme!

// This is a view that shows user profile
struct ProfileView: View {
    var body: some View {
        // VStack to arrange elements vertically
        VStack {
            // Display the user's name
            Text(user.name)
                // Make the text larger
                .font(.title)

            // Show the user's email
            Text(user.email)
        }
    }
}

// Function to save data
func saveData() {
    // Create a URL
    let url = getDocumentsDirectory().appendingPathComponent("data.json")

    // Try to write data
    do {
        try data.write(to: url)
    } catch {
        // Print error if it fails
        print(error)
    }
}

/// ProfileView displays and allows editing of user information
/// 
/// Accessibility notes:
/// - All fields have appropriate labels for VoiceOver
/// - Dynamic Type is fully supported for all text elements
/// - Contrast ratios exceed WCAG AAA requirements
struct ProfileView: View {
    // MARK: - Properties
    @StateObject private var viewModel = ProfileViewModel()
    @Environment(\.dismiss) private var dismiss

    // MARK: - View Body
    var body: some View {
        Form {
            // Personal information section uses different validation rules
            // depending on the user's account type (personal vs. business)
            Section("Personal Information") {
                personalInfoSection
            }

            // Account settings only visible for accounts older than 30 days
            // due to security policy requirements
            if viewModel.accountAgeInDays > 30 {
                Section("Account Settings") {
                    accountSettingsSection
                }
            }

            // Password reset intentionally separated to emphasize security importance
            Section {
                passwordResetSection
            }
        }
        .navigationTitle("Profile")
        /*
         * We're using a custom back button to prevent data loss when user
         * taps back with unsaved changes. This shows a confirmation dialog
         * when appropriate and handles the special case of account deletion.
         */
        .navigationBarBackButtonHidden(true)
        .toolbar {
            ToolbarItem(placement: .navigationBarLeading) {
                customBackButton
            }
        }
    }

    // MARK: - Helper Views

    /* Extracted subviews with their own comments... */
}

/// Saves user data with conflict resolution and backup creation
/// 
/// - Important: This method implements Apple's data protection best practices 
///   including atomic writes and backup creation.
/// 
/// - Note: For large datasets, consider using the batch save alternative
///   which processes data in chunks to avoid memory pressure.
func saveData() {
    // Create backup before saving in case the operation fails
    // This prevents data loss if the app is terminated during save
    createBackup()

    let url = getDocumentsDirectory().appendingPathComponent("data.json")

    // Using atomic write to prevent data corruption if the app
    // is terminated during the write operation
    do {
        try data.write(to: url, options: .atomic)
        removeBackupIfNeeded()

        // Log analytics only in non-private scenarios
        if !UserDefaults.standard.bool(forKey: "privateMode") {
            Analytics.logEvent("data_saved", parameters: ["size": data.count])
        }
    } catch {
        // Restore from backup if the save operation failed
        restoreFromBackup()
        handleError(error)
    }
}