swift - 读取 UITextfields 的值时出错

Question

我在读取文本字段中的值时遇到问题。每次我在这一行中输入 let username = UsernameTextField.text 时，我都会收到一条错误消息“无法在属性初始值设定项中使用实例成员‘UsernameTextField’；属性初始值设定项在‘self’可用之前运行”。

完整代码如下:

import UIKit

class SignInViewController: UIViewController,UITextFieldDelegate {
    @IBOutlet var UsernameTextField: UITextField!
    @IBOutlet var PasswordTextField: UITextField!
    @IBOutlet var LogInButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
        navigationController?.navigationBar.shadowImage = UIImage()
        navigationController?.navigationBar.isTranslucent = true
        navigationController?.view.backgroundColor = UIColor.clear
        // Remove Autocorrection Type
        UsernameTextField.autocorrectionType = .no
        PasswordTextField.autocorrectionType = .no
        PasswordTextField.textContentType = UITextContentType("")
        //Next button takes user to the next textfield
        UsernameTextField.delegate = self
        PasswordTextField.delegate = self
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if textField == UsernameTextField{
            PasswordTextField.becomeFirstResponder()

        } else if textField == PasswordTextField {
            self.view.endEditing(true)
        }
        return true
    }

    let username = UsernameTextField.text
}

Answer 1

这就是您所拥有的，设置文本的调用不在函数中。

func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    if textField == UsernameTextField{
        PasswordTextField.becomeFirstResponder()

    } else if textField == PasswordTextField {
        self.view.endEditing(true)
    }
    return true
}

let username = UsernameTextField.text // THIS IS NOT IN A FUNCTION

移到这里:

func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    if textField == UsernameTextField{
        PasswordTextField.becomeFirstResponder()
    } else if textField == PasswordTextField {
        self.view.endEditing(true)
    }
    let username = UsernameTextField.text // THIS IS NOW IN A FUNCTION    
    return true
}