Swift Rules

Version: Swift 6 / 6.2

Tooling

• Build: Swift Package Manager or Xcode
• Testing: XCTest with coverage >= 85%
• Linting: SwiftLint

Best Practices (2026)

• Use "Approachable Concurrency" philosophy (Swift 6.2)
• Use @MainActor for UI code - guarantees main thread execution
• Use .task {} modifier - auto-cancels when view disappears
• Use actors for mutable state isolation
• Mark types as Sendable for cross-concurrency-domain safety

Swift 6.2 Concurrency

// Default MainActor isolation for modules
// Enable: -default-isolation MainActor

// Explicit concurrent execution
@concurrent
func processData() async -> Data {
    // Runs in parallel, not on MainActor
}

// Nonisolated async inheritance
// Inherits caller's actor instead of own isolation
nonisolated func helper() async {
    // Inherits isolation from caller
}

SwiftUI Patterns

• @State for local state
• @Binding for parent-child communication
• @Observable (macro) for external state (iOS 17+)
• Use NavigationStack with .navigationDestination for type-safe navigation

Progressive Disclosure

Swift 6.2 principle: Only learn concurrency concepts as you need them:

1. Sequential code first
2. Add async/await for suspending APIs
3. Add actors/Sendable only when introducing parallelism

MoAI Integration

• Use Skill("moai-lang-swift") for detailed patterns
• Follow TRUST 5 quality gates