Passing value over to next viewController

Question

I am currently writing an app in Swift and I implemented all my UI programatically. I would it kind of exhausting, so recently I decided to use storyboard but I am stuck with a bug.

When passing over the mainContext from the AppDelegate to the FirstViewController, the value of the mainContext is nil. In the first place, when I wrote everything programmatically, my code looked like this:

        let vc = FirstViewController()
        vc.mainContext = mainContext
        window?.rootViewController = vc

But now that I am working with StoryBoard, this is not valid anymore because I have to instantiate the view with its ID, like this:

            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            var vc = storyboard.instantiateViewControllerWithIdentifier("FirstView") as! FirstViewController
            vc.mainContext = mainContext

But in this case, the context is nil. If I don't instantiate the VC like this, my outlets are nil and I get this error:

fatal error: unexpectedly found nil while unwrapping an Optional value

Does someone know a way to pass my mainContext?

Answer 1

You're not accessing the rootViewController, you're creating a new view controller and not doing anything with it, to access the rootViewController replace this

let storyboard = UIStoryboard(name: "Main", bundle: nil)
var vc = storyboard.instantiateViewControllerWithIdentifier("FirstView") as! FirstViewController
vc.mainContext = mainContext

with

if let vc = self.window?.rootViewController as? FirstViewController {
    vc.mainContext = mainContext
}