Semaphore | Delay splash screen in iOS + Objective C

• How to wait for an asynchronously dispatched block to finish?
• How to integrate semaphore in iOS?
• How to delay splash screen for longer time, so that developer can prefetch or execute something before start of iOS App.

The answer of all the above questions is SEMAPHORE.  A semaphore is a variable or abstract data type used to control access to a common resource by multiple processes in a concurrent system such as a multiprogramming operating system. 

Suppose you want to perform some task before root view controller is shown to user. 

Goto AppDelegate's method didFinishLaunchingWithOptions, create a method as below:- 

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

    [self performTaskToDelaySplash];

}

-(void) performTaskToDelaySplash {

    

    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0); //1. Create semaphore

    

//Perform your task here, i.e Any webservice call or any database operation

         dispatch_semaphore_signal(semaphore); //3, write this line when your task completes

    while (dispatch_semaphore_wait(semaphore, DISPATCH_TIME_NOW)) { //2

        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:100]];

    }

}

Stackover flow reference post.