OS X storyboard 在 applicationDidFinishLaunching 之前调用 viewDidLoad

Question

I created a Mac OS X application in Xcode using storyboards. For some reason the applicationDidFinishLaunching method in the AppDelegate is being called after viewDidLoad in the NSViewControllers. As with iOS apps, I thought viewDidLoad is supposed to be called before applicationDidFinishLaunching ? Do storyboards in OS X apps initialize the view controllers before the app has finished launching?

I am using the applicationDidFinishLaunching method to register default settings into NSUserDefaults. Unfortunately, registering the default values is happening after the views in the storyboard are loaded. Therefore, when I set up the view in each view controller using viewDidLoad , the defaults data in NSUserDefaults has not been set. If I can't use applicationDidFinishLaunching to register NSUserDefaults in OS X storyboard apps, then how I set the defaults before viewDidLoad is called?

To fix this issue, in the Main.storyboard in Xcode, I turned off "Is Initial Controller" for the main window. I assigned a storyboard ID to the main window as "MainWindow". Then in the AppDelegate I entered the following code:

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    func applicationDidFinishLaunching(aNotification: NSNotification) {

        let storyboard = NSStoryboard(name: "Main", bundle: nil)
        let mainWindow = storyboard.instantiateControllerWithIdentifier("MainWindow") as! NSWindowController
        mainWindow.showWindow(nil)
        mainWindow.window?.makeKeyAndOrderFront(nil)

    }
}

The app does not crash but now the window never appears. The following image displays the storyboard I'm working with:

Answer 1

Correct, the lifecycle is a wee bit different in OS X.

Instead of letting the storyboard be your initial interface (this is defined in the General settings of your project), you can instead set up a MainMenu xib file and designate that as your main interface, then in your applicationDidFinishLaunching method in your AppDelegate you can programmatically instantiate your storyboard after you have completed your other initialization code.

I recommend checking out Cocoa Programming for OS X: The Big Nerd Ranch Guide if you haven't already; one nice thing they do in their book is actually have you get rid of some of the default Xcode template stuff and instead they have you set up your initial view controller the "right" way by doing it explicitly.

You might put something like this in your applicationDidFinishLaunching:

NSStoryboard *mainStoryboard = [NSStoryboard storyboardWithName:@"Main" bundle:nil];
MyWindowController *initialController = (MyWindowController *)[mainStoryboard instantiateControllerWithIdentifier:@"myWindowController"];
[initialController showWindow:self];
[initialController.window makeKeyAndOrderFront:self];

This assumes that you've already changed "Main Interface" to something like MainMenu.xib.

Answer 2

As the question's author mentioned:

The app does not crash but now the window never appears.

Despite Nicolas and Aaron both helpful answers (I already adquire the book you recommended, Aaron, and will start implementing the two-storyboard pattern your way, Nicolas), neither solve the specific problem of the window not showing.

Solution

You need make your WindowController instance live outside applicationDidFinishLaunching(_:) 's scope. To accomplish it, you could declare a NSWindowController propriety for your AppDelegate class and persist your created WindowController instance there.

Implementation

In Swift 4.0

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    var mainWindowController: NSWindowController?

    func applicationDidFinishLaunching(_ aNotification: NSNotification) {

        let storyboard = NSStoryboard(name: NSStoryboard.Name(rawValue: "Main"), bundle: nil)
        let mainWindow = storyboard.instantiateController(withIdentifier: NSStoryboard.SceneIdentifier(rawValue: "MainWindow")) as! NSWindowController
        mainWindow.showWindow(self)
        mainWindow.window?.makeKeyAndOrderFront(self)

        // After applicationDidFinishLaunching(_:) finished, the WindowController instance will persist.
        self.mainWindowController = mainWindow
    }
}

Answer 3

In addition to Aaron's answer , I found out that the separate Interface Builder file containing the menu alone (separate from the window and view controller) does not need to be a xib; it too can be a storyboard. This enables us to easily fix as follows:

1. Duplicate your original storyboard (Main.storyboard) and rename it to " Menu .storyboard"
2. Delete the window controller and view controller from Menu.storyboard
3. Delete the app menu bar from Main.storyboard.
4. Change your app target's "Main Interface" from "Main.storyboard" to "Menu.storyboard".

(I tried it in my app and it works)

This avoids having to re-create the app's main menu from scratch, or to figure out how to transplant your existing one from "Main.stroyboard" to "Menu.xib".

Answer 4

The other solution is registering NSApplicationDidFinishLaunchingNotification in your view controllers and move your code from viewDidLoad to applicationDidFinishLaunchingNotification:

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(applicationDidFinishLaunchingNotification:)
                                             name:NSApplicationDidFinishLaunchingNotification
                                           object:nil];

Answer 5

Based on my previous answer here

If you want a piece of code to be run before everything, you can override the AppDelegate 's init() like this:

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    override init() {
        DoSomethingBeforeEverthing()       // You code goes here
        super.init()
    }
...
}

Few points to remember:

1. You might want to check, what's allowed/can be done here, ie before app delegate is initialized
2. Also cleaner way would be, subclass the AppDelegate , and add new delegate method that you call from init, say applicationWillInitialize and if needed applicationDidInitialize