Additions library provides an ordered way to perform application boot tasks. The main components of the boot process are:
Here's example sequence diagram from an app launched using AppTasks:
To understand better each step, keep on reading.
AppTasks provides an object that manages setup tasks when booting the application. When setup tasks are running, it buffers AppDelegate delegate method calls, when setup tasks are finished, it forwards buffered AppDelegate calls, and it keeps sending further AppDelegate calls to observing tasks.
You must create this object on your SceneDelegate or AppDelegate in order to forward application events.
class AppDelegate: UIResponder, UIApplicationDelegate {
private var appServices = AppServices()
/// In this case we are getting an instance of `AppTasks` by building it, but after it is built, we can also get it by calling: `AppTasks.shared`
private lazy var tasks = AppTasks.build(serviceProviders: [AdditionsServices(), appServices]) {
print("all tasks completed")
}
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
/// Calls to `didFinishLaunching` and other delegate methods must be redirected to the array of `tasks` we received from building an `AppTasks` object, so that they can be buffered and forwarded to the currently registered tasks. We will do the same for all `AppDeleagte` delegate calls.
tasks.forEach {
_ = $0.application?(application, didFinishLaunchingWithOptions: launchOptions)
}
return true
}
}To take advantage of the ServiceLocator that Additions provides, you must create a subclass of ServiceProvider. It is in charge of building the necessary components for AppTasks to work.
It is also where we’ll define in which order tasks must be ran.
import Additions
class AppServices: ServiceProvider {
private lazy var onboardingScreenTask = OnboardingScreenTask()
private lazy var homeScreenTask = HomeScreenTask()
private lazy var pushNotoificationTask = PushNotoificationTask()
lazy var appTasks: [AppTask] = {
/// We need to present onboarding screens before showing the home screen, so we add a dependency from `homeScreenTask` to `onboardingScreenTask` this way, `homeScreenTask` won't be ran until `onboardingScreenTask` calls the `setFinished()` method.
homeScreenTask.addDependency(onboardingScreenTask)
return [
onboardingScreenTask,
homeScreenTask,
pushNotoificationTask
]
}()
/// `modules` method implementation is required by the `ServiceLoactor` protocol.
func modules() -> [Register] {
/// If we want to use `@Inject` to have the stored instance of a task injected to an other class, we can do so by registering it with the `ServiceLocator`.
return [
Register { homeScreenTask }
]
}
}An AppTask is an NSOperation subclass that needs to be performed before any AppDelegate or SceneDelegate call is performed.
To create an AppTask you must provide an object that conforms to AppTask , overrides its main() method, and calls setFinished() when it finishes the process.
Since these tasks are NSOperations, you can create various dependencies between them, and when submitted to AppTasks, they can even execute in parallel if the dependencies are set up in that way.
/// Conform to `AppTask`
class OnboardingScreenTask: AppTask {
private let onboardingNavigator: OnboardingNavigator
init(onboardingNavigator: OnboardingNavigator) { ... }
/// Override `main()`
override func main() {
/// Presents onboarding screens
onboardingNavigator.navigate(completion: {
/// Call `setFinisehd()` when onboarding is completed.
self.setFinished()
})
}
}A NoOpTask is a task that finishes immediately. The use of this kind of task is to receive and react to AppDelegate delegate calls. It will keep receiving these events throught the app’s lifecycle.
/// Conform to `AppTask`
class PushNotoificationTask: NoOpTask {
private let pushService: PushService
init(pushService: PushService) { ... }
func application(
_ application: UIApplication,
didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
pushService.application(
application,
didRegisterForRemoteNotificationsWithDeviceToken: deviceToken
)
}
}