Private func didFinishLaunchingWithOptions not being called? (Swift 3)

Question

Isn't didFinishLaunchingWithOptions supposed to be called when the app starts running for the first time? I set a breakpoint at this method and when I run the app in the simulator the breakpoint doesn't get hit, which means the method doesn't get called. I'm trying to load some data from UserDefaults whenever the app launches, but it's being completely ignored. One thing I noticed is that it's by default a private func instead of a func. If I get rid of the private, I receive a warning that "there's an almost similar optional requirement in the UIApplicationDelegate". Can someone explain to me what this means and whether or not the private func has anything to do with the method being ignored? Is that method even supposed to be called when I run my app in the simulator? If not, how can I test if data is being retrieved after my app launches? All the other methods in the AppDelegate do get called normally (for example, the applicationDidEnterBackground method works perfectly fine).

Answer 1

Remove your method signature and have Xcode autocomplete it

I also had the problem that my didFinishLaunchingWithOptions method in AppDelegate would not be called. My function was also marked private and looked like this

private func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool

The problem is that this is the old syntax! Apparently for me when I converted my project from Swift 2.x to Swift 3 Xcode did not convert the methods in AppDelegate. The new syntax looks like this

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool

Swift 4.2:

func application( _ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool

Answer 2

This method is defined in the ApplicationDelegate and it will always be called once the app is launched. If you have not defined the method again in any ViewController and the one in AppDelegate is not being called, then try resetting the simulator.

Open simulator - > menu Simulator -> Reset content and settings.

-(BOOL)application(UIApplication*)applicationdidFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
//..
}

Answer 3

Update for Swift 4.2:

func application(
    _ application: UIApplication, 
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool

Answer 4

for Swift ~3.0 Replace didFinishLaunchingWithOptions with follwing signature

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool {
}