ax-background-tasks

Background Tasks

Quick Patterns

// BGAPPREFRESH (iOS 13+) - keep content fresh, ~30s runtime
// Info.plist: BGTaskSchedulerPermittedIdentifiers + UIBackgroundModes=fetch

// Register in didFinishLaunchingWithOptions BEFORE return
BGTaskScheduler.shared.register(
    forTaskWithIdentifier: "com.app.refresh", using: nil
) { task in
    self.handleRefresh(task: task as! BGAppRefreshTask)
}

// Schedule when app backgrounds
let request = BGAppRefreshTaskRequest(identifier: "com.app.refresh")
request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)
try BGTaskScheduler.shared.submit(request)

// Handler
func handleRefresh(task: BGAppRefreshTask) {
    task.expirationHandler = { self.cancel() }  // set FIRST
    scheduleNextRefresh()                        // continuous pattern
    fetchData { result in
        task.setTaskCompleted(success: result.isSuccess)  // ALL paths
    }
}

// BGPROCESSINGTASK (iOS 13+) - maintenance, minutes runtime
// Info.plist: UIBackgroundModes=processing
let req = BGProcessingTaskRequest(identifier: "com.app.maintenance")
req.requiresExternalPower = true   // CPU-intensive work
req.requiresNetworkConnectivity = true  // cloud sync

// BGCONTINUEDPROCESSINGTASK (iOS 26+) - user-initiated continuation
let req = BGContinuedProcessingTaskRequest(
    identifier: "com.app.export.photos",
    title: "Exporting Photos", subtitle: "0 of 100"
)
req.strategy = .fail  // reject if can't start now

// BACKGROUND URLSESSION - survives app termination
let config = URLSessionConfiguration.background(withIdentifier: "com.app.dl")
config.sessionSendsLaunchEvents = true
config.isDiscretionary = true
let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)

// BEGINBACKGROUNDTASK - ~30s for state saving on background
let id = UIApplication.shared.beginBackgroundTask { UIApplication.shared.endBackgroundTask(id) }
saveState { UIApplication.shared.endBackgroundTask(id) }

// SWIFTUI backgroundTask modifier
.backgroundTask(.appRefresh("com.app.refresh")) {
    scheduleNext()
    await fetchContent()  // completes when closure returns
}