SwiftUI Development

Key Principles

• Follow the user's requirements carefully and to the letter
• First think step-by-step - describe your plan for what to build in pseudocode, written out in great detail
• Confirm your understanding, then write code
• Write correct, up-to-date, bug-free, fully functional, working, secure, performant, and efficient code
• Focus on readability over being performant
• Fully implement all requested functionality
• Leave NO TODOs, placeholders, or missing pieces in the code
• Be concise. Minimize any other prose
• If you think there might not be a correct answer, say so. If you do not know the answer, say so instead of guessing

Architecture

• Use MVVM (Model-View-ViewModel) architecture
• Implement protocol-oriented programming
• Prefer structs over classes for data models
• Use extensions for code organization and separation of concerns
• Leverage Swift's type system and generics effectively

SwiftUI View Structure

• Keep views small and focused on a single responsibility
• Extract reusable components into separate views
• Use ViewBuilder for complex conditional view logic
• Implement proper view composition patterns
• Use @ViewBuilder for custom container views

State Management

• Use @State for local view state
• Use @Binding for two-way data binding with child views
• Use @StateObject for view-owned observable objects
• Use @ObservedObject for passed-in observable objects
• Use @EnvironmentObject for dependency injection
• Use @Environment for system values
• Use @Published in ObservableObject classes
• Leverage the new @Observable macro (iOS 17+)

Naming Conventions

• Use camelCase for variables, functions, and methods
• Use PascalCase for types (classes, structs, enums, protocols)
• Use descriptive, meaningful names
• Prefix boolean variables with is, has, should, etc.
• Use verb phrases for function names

SwiftUI Best Practices

• Always use the latest SwiftUI features and syntax
• Use SF Symbols for system icons
• Implement proper dark mode support
• Support Dynamic Type for accessibility
• Use semantic colors from the asset catalog
• Implement proper keyboard avoidance
• Use NavigationStack (iOS 16+) over NavigationView

Layout and Styling

• Use native SwiftUI layout containers (VStack, HStack, ZStack, Grid)
• Leverage LazyVStack and LazyHStack for performance
• Use GeometryReader sparingly and only when necessary
• Implement adaptive layouts for different screen sizes
• Use ViewModifiers for reusable styling
• Create custom ButtonStyles, TextFieldStyles, etc.

Animations and Transitions

• Use withAnimation for state-driven animations
• Implement custom transitions using AnyTransition
• Use matchedGeometryEffect for hero animations
• Prefer implicit animations with .animation modifier
• Use spring animations for natural feel

Data Flow

• Use async/await for asynchronous operations
• Implement proper error handling with Result type
• Use Combine for reactive data streams when appropriate
• Handle loading, error, and success states properly
• Use Task for async work in views

Performance Optimization

• Minimize view body recalculations
• Use equatable conformance where appropriate
• Implement proper list diffing with identifiable items
• Use @MainActor for UI updates
• Profile with Instruments before optimizing
• Cache expensive computations

Accessibility

• Add proper accessibility labels
• Implement accessibility hints
• Support VoiceOver
• Use accessibility traits appropriately
• Test with accessibility features enabled

Testing and Previews

• Create comprehensive preview providers
• Use #Preview macro for multiple configurations
• Test in different color schemes
• Preview on multiple device sizes
• Use preview data for realistic testing

Code Quality

• Write self-documenting code
• Add comments for complex logic only
• Follow Swift API Design Guidelines
• Use guard for early returns
• Handle optionals safely without force unwrapping

Common Patterns

View with ViewModel

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

    var body: some View {
        // View implementation
    }
}

@MainActor
class ContentViewModel: ObservableObject {
    @Published var items: [Item] = []
    @Published var isLoading = false

    func loadItems() async {
        isLoading = true
        // Load items
        isLoading = false
    }
}

Reusable View Modifier

struct CardModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .padding()
            .background(Color(.systemBackground))
            .cornerRadius(12)
            .shadow(radius: 4)
    }
}

extension View {
    func cardStyle() -> some View {
        modifier(CardModifier())
    }
}