IBOutlet is nil, but it is connected in storyboard, Swift

Typically this happens because your view controller hasn't loaded its view hierarchy yet. A view controller only loads its view hierarchy when something sends it the view message. The system does this when it is time to actually put the view hierarchy on the screen, which happens after things like prepareForSegue:sender: and viewWillAppear: have returned.

Since your VC hasn't loaded its view hierarchy yet, your outlets are still nil.

You could force the VC to load its view hierarchy by saying _ = self.view.

Did you instantiate your view controller from a Storyboard or NIB, or did you instantiate it directly via an initializer?

If you instantiated your class directly with the initializer, the outlets won't be connected. Interface Builder creates customized instances of your classes and encodes those instances into NIBs and Storyboards for repeated decoding, it doesn't define the classes themselves. If this was your problem, you just need to change the code where you create your controller to instead use the methods on UIStoryboard, or UINib.

Have you tried running Product > Clean. Solved a very similar problem for me.