正确使用UIViewController中的present

我遇到了一个问题,我不能在我的类中使用“self”呈现动态UIViewController。它告诉我“类型的值”(LoginScreenVC)->()->(LoginScreenVC)'没有成员“视图”。

它将使用一个闭包,例如。 if let loginScreen = UIStoryBoard ... ,但由于要切换到的UIViewController是动态的,因此无法将其强制转换为特定的UIViewController。

是否有其他方式显示ViewController?

SWIFT 4.2/XCode 10.1

import UIKit

class LoginScreenVC: UIViewController {
    let myTokenHandler = TokenHandler()

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func loginButton(_ sender: Any) {
        print("Login button pressed")

        let usernameInputField = self.view.viewWithTag(6548) as! UITextField
        let passwordInputField = self.view.viewWithTag(6549) as! UITextField

        userInput = usernameInputField.text!
        passInput = passwordInputField.text!

        // call completion handler
        requestToken(success: handlerBlock)

    }
    // completion handler step 1: request token and get redirect string to switch screen
    func requestToken(success: (String) -> Void) {
        let requestResult = myTokenHandler.requestToken(password: passInput, username: userInput)
        success(requestResult)
    }

    // completion handler step 2: use redirect string to switch screen
    let handlerBlock: (String) -> Void = { redirect in
            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            let loginScreen = storyboard.instantiateViewController(withIdentifier: redirect)
            self.present(loginScreen, animated: true, completion: nil) //Value of type '(LoginScreenVC) -> () -> (LoginScreenVC)' has no member 'view'
    }
}