Is rootViewController always ready to present a segue by the time application:didBecomeActive is called (iOS)?

问题

My app has a rootViewController setup in a storyboard. I originally asked this question, but I can see that it is the wrong question to ask now:

Is the viewDidLoad method of the rootViewController always called before application:didBecomeActive in the app delegate? Does that viewDidLoad method always finish before application:didBecomeActive is called, or can the two run concurrently?

I can run tests, but I know that these tests don't take into account every situation. I want to understand if there are hard and fast rules that apply here, or if I might possibly be dealing with race conditions at some point. From what I can tell, viewDidLoad of the rootViewController seems to be called and finished before application:didbecomeActive is called, but I can't figure out if this is something I can rely on.

I am using iOS 11 and Xcode 9.

My rootViewController serves to show my appUpdating view, passcode view, my legal terms view, my handleImportedFile view, and my tabbarcontroller. It is like a launch coordinator of sorts, because my loading process is extremely complicated. Now I am moving the location of the user's sqlite database, and some of my user's databases are huge. It has to be done in the background, but while a hud is running on the main queue, because the app cannot show data until this is done. If I do this during application:didFinishLaunchingWithOptions, some users are getting the watchdog timer. So I want to move the loading process to application:didBecomeActive (I have a flag to tell me if app is launching from terminated). When it is done running, the rootViewController performs a segue to the pertinent view. But I think rootViewController needs to have loaded by that time, and I am not sure that that is always the case.

Basically, in the code below, I am trying to figure out if [self.masterController showApplicableView], which causes the rootViewController (which I call masterController) to perform a segue, is called in a 'safe place', or if, in any case, it could possibly be too early to have the rootViewController perform a segue at this point.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    self.masterController = (MasterViewController*)self.window.rootViewController;
    self.activatingFromTerminated = YES;

    return YES;
}

- (void)applicationWillEnterForeground:(UIApplication *)application {

    self.activatingFromTerminated = NO;
}

- (void)applicationDidBecomeActive:(UIApplication *)application {

    if (_activatingFromTerminated) {

        self.activatingFromTerminated = NO;

        [[CoreDataController sharedManager] loadStoreWithCompletionHandler:^(NSError * _Nullable error) {

            if ([CoreDataController sharedManager].storeLoaded) {

                [self.masterController showApplicableView];//performs applicable segue
            }
        }];
    }
}

回答1:

From what I can tell, viewDidLoad of the rootViewController seems to be called and finished before application:didbecomeActive is called, but I can't figure out if this is something I can rely on.

It isn’t and you shouldn’t. You shouldn’t be concerned about this at all. The fact that you think you need to know this is a Bad Smell in your code. These are lifetime events from two completely different areas (the app and a view controller) and their relative timing should be no concern of yours. Do in each what is appropriate to the meaning of that event.

来源：https://stackoverflow.com/questions/51884528/is-rootviewcontroller-always-ready-to-present-a-segue-by-the-time-applicationdi

标签

ios

rootviewcontroller