IOS self.window - when is it created?

Question

when you launch your application using a single presentation template and you add NSLog(@"self.window = %@", self.window); in the first line of the AppDelegate.m application: didFinishLaunchingWithOptions: method, you can see that self.window exists in your application.

However, when you launch your application using an empty template and try to write self.window to the console, the result returns null . Even if you add a storyboard and a view controller and set your view controller as the initial view controller and try to register self.window , the result will be the same - its value will be set to null .

And note that no matter which method you choose, you may find that you are declaring @property (strong, nonatomic) UIWindow *window; in AppDelegate.h by default. Therefore, I wonder why in the first case you can see that self.window initialized and sets a value, but not in the latter case. Also, if self.window already declared and initialized in the first case, but NOT in the second case, how can I find the initialization code?

It appears that in both cases the @property declaration is the same - and in both cases, as I mentioned, I tried to write the value of self.window to the FIRST LINE of the AppDelegate.m application: didFinishLaunchingWithOptions: method.

So, is there anything that I am missing? I do not know why these two cases act differently, despite the fact that I did not find differences in the code and the storyboard.

I am using iOS 7 and Xcode 5. Thanks.

Answer 1

OK, when you create a project using Storyboard or Nib, then the project parameters tell the project that the / nib storyboard is the "Main Interface".

This launches the application to load this interface at startup. This is why self.window is created in these cases.

When creating an empty application, there is no interface to install as the main interface.

Then you need to create a window yourself, like this ...

 -(void)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; UIViewController *someController = [UIViewController... //create your initial controller [self.window addSubview:navigationController.view]; [self.window makeKeyAndVisible]; } 

Something like this anyway. That was the time.

Alternatively, if you create an empty application and then add the nib file that you want to use as the initial nib, you can select it in the project settings.

In the goal as a whole. In the "Deployment Information" section, select the "Main Interface" from the tips in your project. Then download this tip when the application starts.

Answer 2

Xcode declares UIWindow as an IBOutlet Object in Appdelegate , and xcode itself intercepts or connects it to the default ViewController.nib window (Xcode is created when creating a non-empty project). There is no need to initialize any object if you declared it as an Iboutlet and linked it to any UIController in nib.

Now in an empty project, if you want to create a window, declare it as an output and connect it to the window available in nib and make AppDelegate as OWner files.