passing data from anonymous closure

I have small question – having 3 classes in Swift:

final class RegisterView: UIView {
    private let firstName: UITextField = {
        let firstName = UITextField()

        // basic setup

        return firstName
}()

final class RegisterViewViewModel {
    var firstName: String = ""
}

final class RegisterViewController: UIViewController {
    
    private let registerView = RegisterView()
    private let viewModel = RegisterViewViewModel()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(registerView)
        registerView.delegate = self
    }
}

How to assign text field value to vm firstName in VC using delegate?