Notification Once perfectly solves the initialization of some modules in application:didFinishLaunchingWithOptions

in the finishing project
AppDelegate , found many written in
- application:didFinishLaunchingWithOptions: The code in is just to get a call opportunity when the program starts, mostly for the initialization of some modules, such as:

- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // ...
    [RunModule setup];
    [[Loca sharedInstance] setup];
    // ...
    return YES;
}

In fact, these codes can be fully exploited
Notification The way to get it inside your own module, share a clever method:

// RunModule.m
+ (void)load
{
    __block id observer =
    [[NSNotificationCenter defaultCenter]
     addObserverForName:UIApplicationDidFinishLaunchingNotification
     object:nil
     queue:nil
     usingBlock:^(NSNotification *note) {
         [self setup]; // Do whatever you want
         [[NSNotificationCenter defaultCenter] removeObserver:observer];
     }];
}

explain:

+ load Method called early enough

The block version of notification registration produces a __NSObserver * object for external remove observers

The block capture of the observer object is earlier than the return of the function, so if __block is not added, it will capture nil

Remove observer at end of block execution without additional cleanup

In this way, the mounting of the code at the program startup point is completed inside the module

It's worth noting that the notification is not sent until the - application:didFinishLaunchingWithOptions: call completes. By the way, here is a suggestion for AppDelegate to slim down: AppDelegate, as a delegate for program-level state changes, should only be used for routing and distribution. The specific logic implementation code should still be in a separate module. This file should be kept clean, except for There should be no other methods outside the method.