Skip to main content

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.

Comments

Popular posts from this blog

How to kill/exit iOS application on a button click programmatically

I had been practising below code to kill an iOS application. exit(0); But last week, my application was rejected by app store due to following reason: We found that your app includes a UI control for quitting the app. This is not in compliance with the iOS Human Interface Guidelines, as required by the App Store Review Guidelines . To avoid any such rebuff, suspend the application using following code snippet. UIApplication.shared.perform(#selector(NSXPCConnection.suspend)) Good news is that now my application is passed the  iOS Human Interface Guidelines and live on app store.

Vector graphics in iOS

In past, designers had to create multiple versions of the same asset (1x, 2x, 3x) to satisfy multiple screen sizes. Using vector assets can save you time because you only have to generate the asset once.  You just need an .xcassets  file in your project for storing your images. In there, you can declare image sets to be “Vectors”. A vector file contains a lot of metadata of an asset that tells the system how to render it's contents, independent of the screen's resolution.  This also means that whenever we get larger screen resolutions, Xcode will be able to scale up your images from your already existing vector PDF for you, giving you automatic support for future devices for free. Steps:- Select “New Image Set” in your  XCAsset. Select the Attributes Inspector in Utilities panel. Under the types drop-down menu, select "Vector" Drag and drop your vector PDF Use the Xcode image catalog image set as you would with any other image. For instance, calling --im

Return multiple values from a function in objective C

We can return tuples in swift as follows:- func getData () -> ( Int , Int , Int ) { //...code here return ( hour , minute , second ) } You can't do that in objective-c. Best option is using parameters by reference . Something like this. - ( void ) getHour :( int *) hour minute :( int *) minute second :( int *) second { * hour = 1 ; * minute = 2 ; * second = 3 ; } And use it like this. int a , b , c ; [ self getHour :& a minute :& b second :& c ]; NSLog (@ "%i, %i, %i" , a , b , c );