//make var users = [String]() a global variable
✔︎ var users = [String]()
class UsersViewController: UIViewController {

    ✘ var users = [String]()

@IBOutlet weak var LibrarianUsername: UITextField!
@IBOutlet weak var LibrarianPassword: UITextField!
@IBOutlet weak var testingLabel: UILabel!

@IBAction func EnterLibrarian(_ sender: Any) {
    let currentUsername = LibrarianUsername.text!
    let currentPassword = LibrarianPassword.text!

    if users.contains(currentUsername) &&
      users.contains(currentPassword) {
        testingLabel.text = "Login Successful"
    } else {
        testingLabel.text = "Username or Password invalid"
    }


}

@IBOutlet weak var NewUsername: UITextField!
@IBOutlet weak var NewPassword: UITextField!

@IBAction func NewUserEnter(_ sender: Any) {
    var newUser = [String]()
    newUser.append(NewUsername.text!)
    newUser.append(NewPassword.text!)
    NewUsername.text = ""
    NewPassword.text = ""
    users.append(contentsOf: newUser)
}