Use the following function to create a timer that keeps working when the app is in background:
func executeAfterDelay(delay: TimeInterval, completion: @escaping(()->Void)){
backgroundTaskId = UIApplication.shared.beginBackgroundTask(
withName: "BackgroundSound",
expirationHandler: {[weak self] in
if let taskId = self?.backgroundTaskId{
UIApplication.shared.endBackgroundTask(taskId)
}
})
let startTime = Date()
DispatchQueue.global(qos: .background).async {
while Date().timeIntervalSince(startTime) < delay{
Thread.sleep(forTimeInterval: 0.01)
}
DispatchQueue.main.async {[weak self] in
completion()
if let taskId = self?.backgroundTaskId{
UIApplication.shared.endBackgroundTask(taskId)
}
}
}
}