ios-performance-battery-patternslisted

# Battery & Performance Patterns Apply these whenever touching widgets, animations, networking, or background work. ## Widgets - Limit `Timeline` entries to **≤ 2** (current + one next-day refresh). More entries run the provider repeatedly and drain battery. - Use `.atEnd` reload policy — let WidgetKit decide when to refresh. ## Animations - Always stop animations in `.onDisappear`. Animations left running off-screen still consume CPU/GPU. - Bind repeating animations to a `@State var isAnimating = false`: set `true` in `.onAppear`, `false` in `.onDisappear`, and pass `value: isAnimating` to `withAnimation`. - Use `.repeatCount(N)` instead of `.repeatForever` for attention animations. ## Low Power Mode Guard expensive operations before they start: ```swift guard !ProcessInfo.processInfo.isLowPowerModeEnabled else { return } ``` Apply to: image preloading, background downloads, video prefetch, heavy sync. ## Network ```swift let config = URLSessionConfiguration.default config.allowsConstrainedNetworkAccess = false // respect Low Data Mode config.allowsExpensiveNetworkAccess = false // avoid cellular when Wi-Fi preferred config.waitsForConnectivity = true // queue rather than fail when offline ``` ## Observer & Task Cleanup `@Observable` macro-generated storage prevents `nonisolated deinit` from removing `NotificationCenter` observers. Use reference-type boxes instead: ```swift final class NotificationObserverBox { private var tokens: [NSObjectPro