Bayyana app da scene lifecycle na iOS a cikin SwiftUI.

Question

IT Interview Practice · Accepted Answer

App na iOS yana wucewa ta **lifecycle phases** — launch, active, background, terminated — kuma SwiftUI yana fallasa su ta `App` protocol da `scenePhase` environment value. Kana haɗawa da waɗannan don ajiye data, dakatar da aiki, da sabunta UI a daidai lokacin.

## Yadda yake aiki

Mashigar app ita ce `struct` da aka yiwa alama `@main` mai bin `App`. Yana dawo da `Scene` ɗaya ko fiye (yawanci `WindowGroup`).

```swift
@main
struct MyApp: App {
    @Environment(\.scenePhase) private var scenePhase

var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .onChange(of: scenePhase) { _, newPhase in
            switch newPhase {
            case .active:    resumeTimers()    // app in foreground, interactive
            case .inactive:  pauseSensitive()  // transitioning (e.g. app switcher)
            case .background: saveState()       // not visible — persist now
            @unknown default: break
            }
        }
    }
}
```

## Matakan scene guda uku

- **`.active`** — a foreground kuma yana karɓar events. Ci gaba da animations, timers, live updates.
- **`.inactive`** — ana gani amma ba ya karɓar events (kira mai shigowa, app switcher). Wani gajeren yanayi na mika mulki.
- **`.background`** — ba a gani. Kana samun ɗan lokaci kaɗan don **ajiye state da 'yantar da resources** kafin yiwuwar termination.

## Matsaloli

- Yi manyan ajiya a `.background`, ba a `.inactive` ba — inactive yana faruwa sau da yawa da sauri.
- Lokacin gudanar da aiki a background yana da iyaka; dogayen ayyuka suna bukatar `BGTaskScheduler`, ba phase handler ba.
- Da tsohon UIKit `AppDelegate`/`SceneDelegate`, callbacks ɗin da suka yi daidai su ne `applicationDidEnterBackground` da makamantansu. SwiftUI na iya haɗawa da su ta `@UIApplicationDelegateAdaptor`.

## Me ya sa yake da muhimmanci

Masu amfani suna sauya apps koyaushe, kuma system na iya kashe app ɗin da ke background ba tare da gargaɗi ba. Amsa daidai ga `scenePhase` shi ne abin da ke sa app ya ji aminci — data marar ajiya yana rayuwa, kuma UI yana sabuntawa lokacin da mai amfani ya dawo maimakon nuna tsohon abu.