Equivalent Storyboard function for Nib - objective-c

Question

I'm trying to convert a project on macOS that uses Storyboards to instantiate a ViewController through a delegate, although I'm running into some difficulty trying to convert it to use a Nib instead.
Currently the storyboard version of the code uses an App Delegate which is associated with two View Controllers. When a button is clicked the front window animates and flips over revealing another (back) window. The code that instantiates the View Controller is:
mainWindow = [NSApplication sharedApplication].windows[0];
secondaryWindow = [[NSWindow alloc]init];
[secondaryWindow setFrame:mainWindow.frame display:false];
// the below is what I'm not sure of - how to reference nib instead of storyboard?
NSStoryboard *mainStoryboard = [NSStoryboard storyboardWithName:#"Main" bundle:[NSBundle mainBundle]];
NSViewController *vc = [mainStoryboard instantiateControllerWithIdentifier:#"BackViewController"];
[secondaryWindow setContentViewController:vc];
I'm not sure the proper way to reference a nib instead of a storyboard in the example shown above. The project I'm trying to convert is located here. I'm really hoping someone can help, thank you!

Answer 1

This is pretty easy to do. Just make an NSViewController subclass (or an NSWindowController subclass if you want it to control a whole window) for each of the two views. For each view, override -init and have it call super's implementation of -initWithNibName:bundle: with the name of the view's nib file:
#implementation MyViewController
- (instancetype)init {
self = [super initWithNibName:#"MyViewController" bundle:nil];
if (self == nil) {
return nil;
}
return self;
}
Note that if you can require a sufficiently recent version of macOS (I think it's 10.11 and higher off the top of my head, but it's possible that I could be off by a version or so), you don't even have to do this much, because NSViewController will automatically look for a nib file with the same name as the class.
Anyway, now you should be able to instantiate a MyViewController and insert its view into your view hierarchy, and manipulate it the same way you'd manipulate any other view:
MyViewController *vc = [MyViewController new];
[someSuperview addSubview:vc.view];
If you want to do windows instead, you can make an NSWindowController subclass instead of NSViewController. NSWindowController is slightly more annoying to use, since its initializers that take nib names are all convenience initializers, whereas the designated initializer just takes an NSWindow. So if you're using, say, Swift, you can't do it the way I did it above with NSViewController. Objective-C, of course, generally lets you do whatever you want, so you actually can get away with just calling super's -initWithWindowNibName:owner:, and I won't tell anyone, wink wink, nudge nudge. However, to be stylistically correct, you probably should just call -initWithWindow: passing nil, and then override windowNibName and owner:
#implementation MyWindowController
- (instancetype)init {
self = [super initWithWindow:nil];
if (self == nil) {
return nil;
}
return self;
}
- (NSNibName)windowNibName {
return #"MyWindowController";
}
- (id)owner {
return self;
}
This should get you a window controller that you can just initialize with +new (or +alloc and -init if you prefer), then call its -window property and manipulate the window as normal.