BaseViewController.swift

class BaseViewController: UIViewController {
    
    private var controller: ViewModelController!
    
    func setViewModel(_ controller: ViewModelController) {
        controller.setViewProviderUnsafe(viewProvider: { [weak self] in
            return self
        })
        self.controller = controller
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        if controller == nil {
            fatalError("\(String(describing: self)) call setViewModel before super.viewDidLoad")
        }
        
        controller.viewCreated()
    }
}