ios-expert

MVVM separates UI logic from business logic using view models that bind to SwiftUI or UIKit views. Structure your app with separate Model, ViewModel, and View layers to improve testability and maintainability. Use property observers or Combine publishers to keep views synchronized with state changes.

SwiftUI offers modern declarative syntax and faster development for iOS 13+, while UIKit provides broader device support and mature ecosystem. Use SwiftUI for new projects targeting recent iOS versions; UIKit when supporting older devices or leveraging extensive third-party libraries. Both can coexist in the same app.

Use Xcode's Instruments to profile CPU, memory, and rendering performance. Common optimizations include reducing view hierarchy depth, lazy-loading data, caching expensive computations, and profiling with Core Animation tools. Test on real devices to catch performance gaps that simulators mask.

Yes, SwiftUI view models are plain Swift classes and can be unit tested independently using XCTest. Mock dependencies, verify state changes, and validate business logic separately from UI rendering. This isolation makes view models highly testable and enables fast test cycles.

Configure signing certificates, provisioning profiles, and bundle identifiers in Xcode project settings. Set version and build numbers, complete app metadata and privacy policies, and test on physical devices. Use App Store Connect to manage releases, TestFlight beta distribution, and submission workflows.

Apple frameworks like CloudKit, HealthKit, and NotificationCenter require entitlements configured in Xcode and user permissions requested at runtime. Use native APIs with proper error handling and background modes for seamless integration. Reference Apple's official documentation and sample code for framework-specific patterns.