iOS background task with all the checks and balances

BackgroundTaskWrapper.swift

class BackgroundTaskWrapper {
    private var taskID = UIBackgroundTaskIdentifier.invalid
    var cancelAction: (() -> Void)?

    func begin() {
        guard .invalid == taskID else { return }
        taskID = UIApplication.shared.beginBackgroundTask { [weak self] in
            self?.cancelAction?()
            self?.end()
        }
    }

    func end() {
        guard .invalid != taskID else { return }
        let id = taskID
        taskID = .invalid
        UIApplication.shared.endBackgroundTask(id)
    }
}