Swift 6 Best Practices Guide

MVVM and VIPER provide layered separation between UI, business logic, and data. MVVM pairs ViewModels with SwiftUI views for reactive state; VIPER isolates concerns across Router, Interactor, Presenter, Entity, and View. Choose MVVM for simpler apps, VIPER for complex domain logic requiring strict boundaries and testability.

Swift 6 enforces structured concurrency through async/await and actors. Use async/await for asynchronous work instead of callbacks; actors isolate mutable state and prevent data races. This eliminates entire classes of concurrency bugs and makes code easier to reason about and test.

Migrate incrementally: refactor to MVVM, extract ViewModels, wrap existing views in SwiftUI containers, then replace incrementally. Pair migration with unit tests for business logic and UI snapshot tests. This reduces risk and maintains app stability throughout the transition.

Dependency injection decouples components, enables mock injection for testing, and improves modularity. Pass dependencies through initializers or use container patterns. It's essential for scaling Swift 6 apps and achieving testability across layers.

Use XCTest with async/await support to test concurrent operations. Mock actors and async functions to isolate units. Combine unit tests for business logic with integration tests for actor interactions and UI snapshot tests for SwiftUI views.

Profile with Instruments to identify bottlenecks in concurrency, memory, and rendering. Modularize via Swift Package Manager to reduce compile times and enable parallel builds. Apply SOLID principles to eliminate circular dependencies and reduce app startup overhead.