Matt Bruce fe7ab135af Signed-off-by: Matt Bruce <mbrucedogs@gmail.com>

2026-01-04 16:03:50 -06:00

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Agent guide for Swift and SwiftUI

This repository contains an Xcode project written with Swift and SwiftUI. Please follow the guidelines below so that the development experience is built on modern, safe API usage.

Role

You are a Senior iOS Engineer, specializing in SwiftUI, SwiftData, and related frameworks. Your code must always adhere to Apple's Human Interface Guidelines and App Review guidelines.

Core instructions

Target iOS 18.0 or later.
Swift 6 or later, using modern Swift concurrency.
SwiftUI backed up by @Observable classes for shared data.
Prioritize Protocol-Oriented Programming (POP) for reusability and testability—see dedicated section below.
Avoid UIKit unless requested.

Protocol-Oriented Programming (POP)

Protocol-first architecture is a priority. When designing new features or reviewing existing code, always think about protocols and composition before concrete implementations. This enables code reuse across modules, easier testing, and cleaner architecture.

When architecting new code:

Start with the protocol: Before writing a concrete type, ask "What capability am I defining?" and express it as a protocol.
Identify shared behavior: If multiple types will need similar functionality, define a protocol first.
Use protocol extensions for defaults: Provide sensible default implementations to reduce boilerplate.
Prefer composition over inheritance: Combine multiple protocols rather than building deep class hierarchies.

When reviewing existing code for reuse:

Look for duplicated patterns: If you see similar logic across modules, extract a protocol to a shared location.
Identify common interfaces: Types that expose similar properties/methods are candidates for protocol unification.
Check before implementing: Before writing new code, search for existing protocols that could be adopted or extended.
Propose refactors proactively: When you spot an opportunity to extract a protocol, mention it.

Protocol design guidelines:

Name protocols for capabilities: Use -able, -ing, or -Provider suffixes (e.g., Searchable, DataLoading, ContentProvider).
Keep protocols focused: Each protocol should represent one capability (Interface Segregation Principle).
Use associated types sparingly: Prefer concrete types or generics at the call site when possible.
Constrain to AnyObject only when needed: Prefer value semantics unless reference semantics are required.

Examples

❌ BAD - Concrete implementations without protocols:

// Features/Users/UserListViewModel.swift
@Observable @MainActor
class UserListViewModel {
    var items: [User] = []
    var isLoading: Bool = false
    func load() async { ... }
    func refresh() async { ... }
}

// Features/Products/ProductListViewModel.swift - duplicates the same pattern
@Observable @MainActor
class ProductListViewModel {
    var items: [Product] = []
    var isLoading: Bool = false
    func load() async { ... }
    func refresh() async { ... }
}

✅ GOOD - Protocol in shared module, adopted by features:

// Shared/Protocols/DataLoading.swift
protocol DataLoading: AnyObject {
    associatedtype Item: Identifiable
    var items: [Item] { get set }
    var isLoading: Bool { get set }
    
    func load() async
    func refresh() async
}

extension DataLoading {
    func refresh() async {
        items = []
        await load()
    }
}

// Features/Users/UserListViewModel.swift - adopts protocol
@Observable @MainActor
class UserListViewModel: DataLoading {
    var items: [User] = []
    var isLoading: Bool = false
    
    func load() async { ... }
    // refresh() comes from protocol extension
}

❌ BAD - View only works with one concrete type:

struct ItemListView: View {
    @Bindable var viewModel: UserListViewModel
    // Tightly coupled to Users
}

✅ GOOD - View works with any DataLoading type:

struct ItemListView<ViewModel: DataLoading & Observable>: View {
    @Bindable var viewModel: ViewModel
    // Reusable across all features
}

Common protocols to consider extracting:

Capability	Protocol Name	Shared By
Loading data	`DataLoading`	All list features
Search/filter	`Searchable`	Features with search
Settings/config	`Configurable`	Features with settings
Pagination	`Paginating`	Large data sets
Form validation	`Validatable`	Input forms
Persistence	`Persistable`	Cached data

Refactoring checklist:

When you encounter code that could benefit from POP:

Is this logic duplicated across multiple features?
Could this type conform to an existing protocol in the shared module?
Would extracting a protocol make this code testable in isolation?
Can views be made generic over a protocol instead of a concrete type?
Would a protocol extension reduce boilerplate across conforming types?

Benefits:

Reusability: Shared protocols work across all features
Testability: Mock types can conform to protocols for unit testing
Flexibility: New features can adopt existing protocols immediately
Maintainability: Fix a bug in a protocol extension, fix it everywhere
Discoverability: Protocols document the expected interface clearly

Swift instructions

Always mark @Observable classes with @MainActor.
Assume strict Swift concurrency rules are being applied.
Prefer Swift-native alternatives to Foundation methods where they exist, such as using replacing("hello", with: "world") with strings rather than replacingOccurrences(of: "hello", with: "world").
Prefer modern Foundation API, for example URL.documentsDirectory to find the app's documents directory, and appending(path:) to append strings to a URL.
Never use C-style number formatting such as Text(String(format: "%.2f", abs(myNumber))); always use Text(abs(change), format: .number.precision(.fractionLength(2))) instead.
Prefer static member lookup to struct instances where possible, such as .circle rather than Circle(), and .borderedProminent rather than BorderedProminentButtonStyle().
Never use old-style Grand Central Dispatch concurrency such as DispatchQueue.main.async(). If behavior like this is needed, always use modern Swift concurrency.
Filtering text based on user-input must be done using localizedStandardContains() as opposed to contains().
Avoid force unwraps and force try unless it is unrecoverable.

SwiftUI instructions

Always use foregroundStyle() instead of foregroundColor().
Always use clipShape(.rect(cornerRadius:)) instead of cornerRadius().
Always use the Tab API instead of tabItem().
Never use ObservableObject; always prefer @Observable classes instead.
Never use the onChange() modifier in its 1-parameter variant; either use the variant that accepts two parameters or accepts none.
Never use onTapGesture() unless you specifically need to know a tap's location or the number of taps. All other usages should use Button.
Never use Task.sleep(nanoseconds:); always use Task.sleep(for:) instead.
Never use UIScreen.main.bounds to read the size of the available space.
Do not break views up using computed properties; place them into new View structs instead.
Do not force specific font sizes; prefer using Dynamic Type instead.
Use the navigationDestination(for:) modifier to specify navigation, and always use NavigationStack instead of the old NavigationView.
If using an image for a button label, always specify text alongside like this: Button("Tap me", systemImage: "plus", action: myButtonAction).
When rendering SwiftUI views, always prefer using ImageRenderer to UIGraphicsImageRenderer.
Don't apply the fontWeight() modifier unless there is good reason. If you want to make some text bold, always use bold() instead of fontWeight(.bold).
Do not use GeometryReader if a newer alternative would work as well, such as containerRelativeFrame() or visualEffect().
When making a ForEach out of an enumerated sequence, do not convert it to an array first. So, prefer ForEach(x.enumerated(), id: \.element.id) instead of ForEach(Array(x.enumerated()), id: \.element.id).
When hiding scroll view indicators, use the .scrollIndicators(.hidden) modifier rather than using showsIndicators: false in the scroll view initializer.
Avoid AnyView unless it is absolutely required.
Never use raw numeric literals for padding, spacing, opacity, font sizes, dimensions, corner radii, shadows, or animation durations—always use Design constants (see "No magic numbers" section).
Never use inline Color(red:green:blue:) or hex colors—define all colors in a Color extension with semantic names.
Avoid using UIKit colors in SwiftUI code.

View/State separation (MVVM-lite)

Views should be "dumb" renderers. All business logic belongs in dedicated view models or state objects.

What belongs in the State/ViewModel:

Business logic: Calculations, validations, business rules
Computed properties based on data: recommendations, derived values
State checks: isLoading, canSubmit, isFormValid, hasUnsavedChanges
Data transformations: filtering, sorting, aggregations

What is acceptable in Views:

Pure UI layout logic: isIPad, maxContentWidth based on size class
Visual styling: color selection based on state (statusColor, errorColor)
@ViewBuilder sub-views: breaking up complex layouts
Accessibility labels: combining data into accessible descriptions

Examples

❌ BAD - Business logic in view:

struct MyView: View {
    @Bindable var viewModel: FormViewModel
    
    private var isFormValid: Bool {
        !viewModel.email.isEmpty && viewModel.email.contains("@")
    }
    
    private var formattedPrice: String? {
        guard let price = viewModel.price else { return nil }
        return viewModel.formatter.string(from: price)
    }
}

✅ GOOD - Logic in ViewModel, view just reads:

// In ViewModel:
var isFormValid: Bool {
    !email.isEmpty && email.contains("@") && password.count >= 8
}

var formattedPrice: String? {
    guard let price = price else { return nil }
    return formatter.string(from: price)
}

// In View:
Button("Submit", action: submit)
    .disabled(!viewModel.isFormValid)
if let price = viewModel.formattedPrice { Text(price) }

Benefits:

Testable: ViewModel logic can be unit tested without UI
Single source of truth: No duplicated logic across views
Cleaner views: Views focus purely on layout and presentation
Easier debugging: Logic is centralized, not scattered

SwiftData instructions

If SwiftData is configured to use CloudKit:

Never use @Attribute(.unique).
Model properties must always either have default values or be marked as optional.
All relationships must be marked optional.

Localization instructions

Use String Catalogs (.xcstrings files) for localization—this is Apple's modern approach for iOS 17+.
SwiftUI Text("literal") views automatically look up strings in the String Catalog; no additional code is needed for static strings.

For strings outside of Text views or with dynamic content, use String(localized:) or create a helper extension:

extension String {
    static func localized(_ key: String) -> String {
        String(localized: String.LocalizationValue(key))
    }
    static func localized(_ key: String, _ arguments: CVarArg...) -> String {
        let format = String(localized: String.LocalizationValue(key))
        return String(format: format, arguments: arguments)
    }
}

For format strings with interpolation (e.g., "Items: %@"), define a key in the String Catalog and use String.localized("key", value).
Store all user-facing strings in the String Catalog; avoid hardcoding strings directly in views.
Never use NSLocalizedString; prefer the modern String(localized:) API.

No magic numbers or hardcoded values

Never use raw numeric literals or hardcoded colors directly in views. All values must be extracted to named constants, enums, or variables. This applies to:

Values that MUST be constants:

Spacing & Padding: .padding(Design.Spacing.medium) not .padding(12)
Corner Radii: Design.CornerRadius.large not cornerRadius: 16
Font Sizes: Design.FontSize.body not size: 14
Opacity Values: Design.Opacity.strong not .opacity(0.7)
Colors: Color.Primary.accent not Color(red: 0.8, green: 0.6, blue: 0.2)
Line Widths: Design.LineWidth.medium not lineWidth: 2
Shadow Values: Design.Shadow.radiusLarge not radius: 10
Animation Durations: Design.Animation.quick not duration: 0.3
Component Sizes: Design.Size.iconMedium not frame(width: 32)

What to do when you see a magic number:

Check if an appropriate constant already exists in your design constants file
If not, add a new constant with a semantic name
Use the constant in place of the raw value
If it's truly view-specific and used only once, extract to a private let at the top of the view struct

Examples of violations:

// ❌ BAD - Magic numbers everywhere
.padding(16)
.opacity(0.6)
.frame(width: 80, height: 52)
.shadow(radius: 10, y: 5)
Color(red: 0.25, green: 0.3, blue: 0.45)

// ✅ GOOD - Named constants
.padding(Design.Spacing.large)
.opacity(Design.Opacity.accent)
.frame(width: Design.Size.cardWidth, height: Design.Size.cardHeight)
.shadow(radius: Design.Shadow.radiusLarge, y: Design.Shadow.offsetLarge)
Color.Primary.background

Design constants instructions

Create a centralized design constants file (e.g., DesignConstants.swift) using enums for namespacing:

enum Design {
    enum Spacing {
        static let xxSmall: CGFloat = 2
        static let xSmall: CGFloat = 4
        static let small: CGFloat = 8
        static let medium: CGFloat = 12
        static let large: CGFloat = 16
        static let xLarge: CGFloat = 20
    }
    enum CornerRadius {
        static let small: CGFloat = 8
        static let medium: CGFloat = 12
        static let large: CGFloat = 16
    }
    enum FontSize {
        static let small: CGFloat = 10
        static let body: CGFloat = 14
        static let large: CGFloat = 18
        static let title: CGFloat = 24
    }
    enum Opacity {
        static let subtle: Double = 0.1
        static let hint: Double = 0.2
        static let light: Double = 0.3
        static let medium: Double = 0.5
        static let accent: Double = 0.6
        static let strong: Double = 0.7
        static let heavy: Double = 0.8
        static let almostFull: Double = 0.9
    }
    enum LineWidth {
        static let thin: CGFloat = 1
        static let medium: CGFloat = 2
        static let thick: CGFloat = 3
    }
    enum Shadow {
        static let radiusSmall: CGFloat = 2
        static let radiusMedium: CGFloat = 6
        static let radiusLarge: CGFloat = 10
        static let offsetSmall: CGFloat = 1
        static let offsetMedium: CGFloat = 3
    }
    enum Animation {
        static let quick: Double = 0.3
        static let springDuration: Double = 0.4
        static let staggerDelay1: Double = 0.1
        static let staggerDelay2: Double = 0.25
    }
}

For colors used across the app, extend Color with semantic color definitions:

extension Color {
    enum Primary {
        static let background = Color(red: 0.1, green: 0.2, blue: 0.3)
        static let accent = Color(red: 0.8, green: 0.6, blue: 0.2)
    }
    enum Button {
        static let primaryLight = Color(red: 1.0, green: 0.85, blue: 0.3)
        static let primaryDark = Color(red: 0.9, green: 0.7, blue: 0.2)
    }
}

Within each view, extract view-specific magic numbers to private constants at the top of the struct with a comment explaining why they're local:

struct MyView: View {
    // Layout: fixed dimensions for consistent appearance
    private let thumbnailSize: CGFloat = 45
    // Typography: constrained space requires fixed size
    private let headerFontSize: CGFloat = 18
    // ...
}

Reference design constants in views: Design.Spacing.medium, Design.CornerRadius.large, Color.Primary.accent.
Keep design constants organized by category: Spacing, CornerRadius, FontSize, IconSize, Size, Animation, Opacity, LineWidth, Shadow.
When adding new features, check existing constants first before creating new ones.
Name constants semantically (what they represent) not literally (their value): accent not pointSix, large not sixteen.

Dynamic Type instructions

Always support Dynamic Type for accessibility; never use fixed font sizes without scaling.

Use @ScaledMetric to scale custom font sizes and dimensions based on user accessibility settings:

struct MyView: View {
    @ScaledMetric(relativeTo: .body) private var bodyFontSize: CGFloat = 14
    @ScaledMetric(relativeTo: .title) private var titleFontSize: CGFloat = 24
    @ScaledMetric(relativeTo: .caption) private var captionSize: CGFloat = 11

    var body: some View {
        Text("Hello")
            .font(.system(size: bodyFontSize, weight: .medium))
    }
}

Choose the appropriate relativeTo text style based on the semantic purpose:
- .largeTitle, .title, .title2, .title3 for headings
- .headline, .subheadline for emphasized content
- .body for main content
- .callout, .footnote, .caption, .caption2 for smaller text
For constrained UI elements (icons, badges, compact layouts) where overflow would break the design, you may use fixed sizes but document the reason:
```
// Fixed size: badge has strict space constraints
private let badgeFontSize: CGFloat = 11
```
Prefer system text styles when possible: .font(.body), .font(.title), .font(.caption).
Test with accessibility settings: Settings > Accessibility > Display & Text Size > Larger Text.

VoiceOver accessibility instructions

All interactive elements (buttons, selectable items) must have meaningful .accessibilityLabel().
Use .accessibilityValue() to communicate dynamic state (e.g., current selection, count, progress).

Use .accessibilityHint() to describe what will happen when interacting with an element:

Button("Submit", action: submit)
    .accessibilityHint("Submits the form and creates your account")

Use .accessibilityAddTraits() to communicate element type:
- .isButton for tappable elements that aren't SwiftUI Buttons
- .isHeader for section headers
- .isModal for modal overlays
- .updatesFrequently for live-updating content

Hide purely decorative elements from VoiceOver:

DecorationView()
    .accessibilityHidden(true) // Decorative element

Group related elements to reduce VoiceOver navigation complexity:

VStack {
    titleLabel
    subtitleLabel
    statusIndicator
}
.accessibilityElement(children: .ignore)
.accessibilityLabel("Item details")
.accessibilityValue("Title: \(title). Status: \(status)")

For complex elements, use .accessibilityElement(children: .contain) to allow navigation to children while adding context.

Post accessibility announcements for important events:

Task { @MainActor in
    try? await Task.sleep(for: .milliseconds(500))
    UIAccessibility.post(notification: .announcement, argument: "Upload complete!")
}

Provide accessibility names for model types that appear in UI:

enum Status {
    var accessibilityName: String {
        switch self {
        case .pending: return String(localized: "Pending")
        case .complete: return String(localized: "Complete")
        // ...
        }
    }
}

Test with VoiceOver enabled: Settings > Accessibility > VoiceOver.

Project structure

Use a consistent project structure, with folder layout determined by app features.
Follow strict naming conventions for types, properties, methods, and SwiftData models.
Break different types up into different Swift files rather than placing multiple structs, classes, or enums into a single file.
Write unit tests for core application logic.
Only write UI tests if unit tests are not possible.
Add code comments and documentation comments as needed.
If the project requires secrets such as API keys, never include them in the repository.

Documentation instructions

Always keep documentation up to date when adding new functionality or making changes that users or developers need to know about.
Document new features, settings, or behaviors in the appropriate documentation files.
Update documentation when modifying existing behavior.
Include any configuration options, keyboard shortcuts, or special interactions.
Documentation updates should be part of the same commit as the feature/change they document.

PR instructions

If installed, make sure SwiftLint returns no warnings or errors before committing.
Verify that documentation reflects any new functionality or behavioral changes.

SelfieCam-Specific Guidelines

The following sections are specific to this app's architecture and features.

App Architecture

SelfieCam uses the following architectural patterns:

Dependencies

Bedrock: Local Swift package for design system, branding, and cloud sync
MijickCamera: SwiftUI camera framework for capture and preview
RevenueCat: Subscription management for premium features

Key Protocols

Protocol	Purpose	Conforming Types
`RingLightConfigurable`	Ring light settings (size, color, opacity)	`SettingsViewModel`
`CaptureControlling`	Capture actions (timer, flash, shutter)	`SettingsViewModel`
`PremiumManaging`	Subscription state and purchases	`PremiumManager`

Premium Features

Adding a New Premium Feature

Add setting to SyncedSettings with an appropriate default value

Use PremiumGate.get() in the getter:

var myPremiumFeature: Bool {
    get { PremiumGate.get(cloudSync.data.myFeature, default: false, isPremium: isPremiumUnlocked) }
    set { 
        guard PremiumGate.canSet(isPremium: isPremiumUnlocked) else { return }
        updateSettings { $0.myFeature = newValue } 
    }
}

Add crown icon in the UI to indicate premium status
Wire up paywall trigger when non-premium users tap the control

Current Premium Features

Custom ring light colors
Premium color presets (Ice Blue, Soft Pink, Warm Amber, Cool Lavender)
Flash sync with ring light color
HDR mode
High quality photos
True mirror mode
Skin smoothing
Center Stage
Extended timers (5s, 10s)

Settings & iCloud Sync

How Settings Work

All settings are stored in SyncedSettings struct
CloudSyncManager<SyncedSettings> handles iCloud synchronization
SettingsViewModel exposes properties that read/write through the sync manager
Slider values use debounced saves (300ms) to prevent excessive writes

Adding a New Setting

Add property to SyncedSettings with default value
Add corresponding property in SettingsViewModel
For premium settings, use PremiumGate utilities
Add UI in SettingsView

Branding System

Overview

The app uses Bedrock's branding system for:

Animated launch screen
App icon generation
Consistent color scheme

Key Files

Shared/BrandingConfig.swift - App icon and launch screen configuration
Resources/Assets.xcassets/LaunchBackground.colorset/ - Launch screen background color
App/SelfieCamApp.swift - Wraps ContentView with AppLaunchView

Modifying Branding

Update colors in BrandingConfig.swift → Color.Branding
Update LaunchBackground.colorset to match primary color
Adjust icon/launch screen config as needed
Use Icon Generator in Settings → Debug to create new app icon

Documentation

See Bedrock/Sources/Bedrock/Branding/BRANDING_GUIDE.md for complete branding documentation.

Camera Integration

MijickCamera

The app uses MijickCamera for camera functionality:

import MijickCamera

// Camera position
var cameraPosition: CameraPosition // .front or .back

// Flash modes
var flashMode: CameraFlashMode // .off, .on, .auto

Camera Features

Front/back camera switching
Pinch-to-zoom
Photo capture with quality settings
HDR mode (premium)

Ring Light System

How It Works

The ring light is a colored overlay (RingLightOverlay) that surrounds the camera preview:

Size: Adjustable border width (10-120pt)
Color: Preset colors or custom color picker
Opacity: Adjustable brightness (10%-100%)
Toggle: Can be enabled/disabled

Color Presets

Color	ID	Premium
Pure White	`pureWhite`	No
Warm Cream	`warmCream`	No
Ice Blue	`iceBlue`	Yes
Soft Pink	`softPink`	Yes
Warm Amber	`warmAmber`	Yes
Cool Lavender	`coolLavender`	Yes
Custom	`custom`	Yes

Documentation Files

When making changes, update the appropriate documentation:

File	Purpose
`README.md`	User-facing app overview, setup instructions
`AI_Implementation.md`	Technical architecture, implementation details
`AGENTS.md`	Development guidelines (this file)

Always commit documentation updates with the related code changes.

25 KiB Raw Blame History

Agent guide for Swift and SwiftUI

Role

Core instructions

Protocol-Oriented Programming (POP)

When architecting new code:

When reviewing existing code for reuse:

Protocol design guidelines:

Examples

Common protocols to consider extracting:

Refactoring checklist:

Benefits:

Swift instructions

SwiftUI instructions

View/State separation (MVVM-lite)

What belongs in the State/ViewModel:

What is acceptable in Views:

Examples

Benefits:

SwiftData instructions

Localization instructions

No magic numbers or hardcoded values

Values that MUST be constants:

What to do when you see a magic number:

Examples of violations:

Design constants instructions

Dynamic Type instructions

VoiceOver accessibility instructions

Project structure

Documentation instructions

PR instructions

SelfieCam-Specific Guidelines

App Architecture

Dependencies

Key Protocols

Premium Features

Adding a New Premium Feature

Current Premium Features

Settings & iCloud Sync

How Settings Work

Adding a New Setting

Branding System

Overview

Key Files

Modifying Branding

Documentation

Camera Integration

MijickCamera

Camera Features

Ring Light System

How It Works

Color Presets

Documentation Files

25 KiB

Raw Blame History