iOS - Universal Applications


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A universal application is an application that is designed for both iPhone and iPad in a single binary. A universal application allows code reuse and fast updates.

Universal Application – Steps Involved

Step 1. Create a simple View based application.

Step 2. Change the File name ViewController.xib file to ViewController_iPhone.xib as shown below in the file inspector in the right hand side.

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Step 3. Select File -> New -> File... then select the subsection "User Interface" and select View. Click Next.

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Step 4. Select the device family as iPad and click next.

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Step 5. Save the file as ViewController_iPad.xib and select Create.

Step 6. Add a label in the center of the screen in both ViewController_iPhone.xib and ViewController_iPad.xib.

Step 7. In ViewController_iPad.xib, select the identity inspector and set the custom class as ViewController.

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Step 8. Update the application:DidFinishLaunching:withOptions method in AppDelegate.m as follows −

- (BOOL)application:(UIApplication *)application
  didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
   self.window = [[UIWindow alloc] initWithFrame:[[UIScreen 
   mainScreen] bounds]];
   // Override point for customization after application launch.
   if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
        self.viewController = [[ViewController alloc] 
        initWithNibName:@"ViewController_iPhone" bundle:nil];
   }
   else{
        self.viewController = [[ViewController alloc] initWithNibName:
        @"ViewController_iPad" bundle:nil];
   }
   self.window.rootViewController = self.viewController;
   [self.window makeKeyAndVisible];
   return YES;
}

Step 9. Update the devices in project summary to Universal as shown below −

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Output

When we run the application, we'll get the following output −

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When we run the application in iPad simulator, we'll get the following output −

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