swift - 我怎样才能用 swift 4 或 5 重写它

Question

我收到一条错误消息，提示“字符”不可用：请直接使用字符串。

extension LoginViewController : UITextFieldDelegate {

    func textField(_ textField: UITextField,
                   shouldChangeCharactersIn range: NSRange,
                   replacementString string: String) -> Bool {

        if let username = self.usernameField.text,
            let password = self.passwordField.text {

            if ((username.characters.count > 0) && //This is where I get the error
                (password.characters.count > 0)) { //This is where I get the error
                self.loginButton.isEnabled = true
            }
        }

        return true
    }

}

我怎样才能解决这个问题？

标签： swift

Answer 1

只需删除.characters

extension LoginViewController : UITextFieldDelegate {

    func textField(_ textField: UITextField,
                   shouldChangeCharactersIn range: NSRange,
                   replacementString string: String) -> Bool {

        if let username = self.usernameField.text,
            let password = self.passwordField.text {

            if username.count > 0 &&
                password.count > 0 {
                self.loginButton.isEnabled = true
            }
        }

        return true
    }

}