Question

当HourGoal和MinuteGoal文本字段为空时，我无法识别代码。它们永远不会出现nil值或为空，导致程序在我尝试打开值时崩溃。

import UIKit

class ReadingGoal: UIViewController {
    @IBOutlet weak var HourGoal: UITextField!
    @IBOutlet weak var MinuteGoal: UITextField!
    @IBOutlet weak var NextButton: UIButton!
    var mingoal = Int()
    var hrgoal = Int()
    var secondstoread:Int = 0
    var initialtime:Int = Int()

    @IBAction func HourEditingDidChange(_ sender: Any) {
        NextButton.isEnabled = true
    }

    @IBAction func MinuteEditingDidChange(_ sender: Any) {
        NextButton.isEnabled = true
    }

    func disable() {
        NextButton.isEnabled = false
    }

    @IBAction func NextButtonIsPressed(_ sender: Any) {
        print("GERALDINE IS AWESOME!!!!!")

        // ERROR
        if HourGoal.text?.isEmpty == false || MinuteGoal.text?.isEmpty == false {
            if HourGoal.text != nil && HourGoal.text?.isEmpty == false{
             //   self.hrgoal = Int(HourGoal.text!)!
                print("hr Value exists")
                print("\(HourGoal.text!)")
            }
            else {
                NextButton.isEnabled = false
            }
            if MinuteGoal.text != nil && MinuteGoal.text?.isEmpty == false{
              // self.mingoal = Int(MinuteGoal.text!)!
                print("min value exists")
                print("\(MinuteGoal.text!)")
            }
            else {
                NextButton.isEnabled = false
            }
            print("in ")
            // secondstoread = ((mingoal + (hrgoal*60))*60)
            secondstoread = 10

            if secondstoread > 0 {
                performSegue(withIdentifier: "Mr.Friar-DavisIsAGiantBallOfFloof", sender: self)
            }
            else {
                NextButton.isEnabled = false
            }
            //function saves text field info to core data
        }
    }

    //for the specific segue 'toBookInfo', certain information is passed through the segue
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        //making sure we are using correct segue
        if segue.identifier == "Mr.Friar-DavisIsAGiantBallOfFloof" {

                //selecting the destination controller
                let detailVC: TimerController = segue.destination as! TimerController

                //sending properties to destination view controller
                detailVC.seconds = secondstoread
            }
    else {
            // Error sender is not a cell or cell is not in collectionView.
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        initialtime = secondstoread
    }
}

Answer 1

这里不会教你术语，但所有变量都应该以 lowerCase 开头，就像这样，甚至IBOutlets ......

......好吧，我研究了你的代码一段时间了：

以任何成本避免使用激励标记!!! - ＆GT;它因为你使用而崩溃的原因！无处不在，那种力量打破了选择权，完全破坏了迅捷的美丽。

这条线如何适用于编译器对选项没有问题？

if HourGoal.text?.isEmpty == false || MinuteGoal.text?.isEmpty == false

你以某种方式检查可选值，并且值肯定为零，所以在代码行提供之前：

guard let hourGoalText = HourGoal.text, let minuteGoal = minuteGoal.text else { //handle code for empty textField
return }

这是检查选项的第一步......现在代码不会崩溃......但老实说没有调试

如果你使用guard let或者let语句，你就不会遇到崩溃问题

Answer 2

您可以通过不同方式检查textfield空虚。其中一些是：

if textField.text?.isEmpty ?? true{
    print("textField is empty")
} 
else{
      print("textField has some text")
}

或

if textfield.text?.characters.count==0 {
  print("textField is empty")
}
else{
     print("textField has some text")
}

或

if textfield.text == "" {
     print("textField is empty")
}
else{
     print("textField has some text")
}

Answer 3

使用if let或guard以安全的方式展开。像这样的东西

if let texthour = HourGoal.text{
       // has text and can be "", next check for blank string
       if texthour == ""{

     }
}

或使用guard作为Dominik显示

不会将Textfield识别为空

3 个答案: