class ViewModel {
    var content: Observable<String?> = Observable(nil)
    
    func seedContent() {
        self.content.value = "Seeded content"
    }
}

class ExampleViewController {
    @IBOutlet weak var contentTextField: UITextField!
    
    let viewModel = ViewModel()
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        self.viewModel.content.bind(for: self, initialFire: true) { newContent in
            self.contentTextField.text = newContent
        }
        self.viewModel.seedContent()
    }
}