xCode解开可选内容时发现nil，即使对其进行了检查

如何解决xCode解开可选内容时发现nil，即使对其进行了检查

非常基本的代码

我在学校做编码，必须创建一个应用程序。该应用程序的一部分是用水量计算器。即使我正在从可选对象中检查nil值，它也会收到错误：“致命错误：在展开可选对象时意外发现了nil”。它会在func btncalculate的随​​机部分期间发现此错误。

import UIKit

class WaterCalcViewController: UIViewController {
    
    
    //Inputs
    @IBOutlet weak var txtShowers: UITextField!
    @IBOutlet weak var txtBaths: UITextField!
    @IBOutlet weak var txtdishwasher: UITextField!
    @IBOutlet weak var txtWashingMachine: UITextField!
    @IBOutlet weak var txtTeeth: UITextField!
    @IBOutlet weak var txtToilet: UITextField!
    @IBOutlet weak var txtNumOfPeople: UITextField!
    //Inputs for the user to add values to their respective use of each item/thing
    
    //Outputs
    
    
    @IBOutlet weak var lblShowerError: UILabel!
    @IBOutlet weak var lblBathError: UILabel!
    @IBOutlet weak var lbldishwasherError: UILabel!
    @IBOutlet weak var lblWashingMachineError: UILabel!
    @IBOutlet weak var lblTeethError: UILabel!
    @IBOutlet weak var lblToiletError: UILabel!
    @IBOutlet weak var lblNumOfPeopleError: UILabel!
    @IBOutlet weak var lblTotalSum: UILabel!
    //Labels that appear when no value is given for their respective text field
    
    //Functions
    
    
    
    
    
    //Actions
    @IBAction func btnBack(_ sender: Any) {
        let destinationVC = self.storyboard?.instantiateViewController(identifier: "tabController") as! UITabBarController
        destinationVC.selectedindex = 3
        destinationVC.modalPresentationStyle = .fullScreen
        self.present(destinationVC,animated: true,completion: nil)
    }
    
    
    
    var success: Int = 0
    
    
    
    
    
    @IBAction func btncalculate(_ sender: Any) {
        success = 0
        let shower: Int? = Int(txtShowers.text!)
        if shower != nil {
            success = success + 1
            
        } else if shower == nil {
            lblShowerError.text = ("Please input a valid number")
        }
        
        let bath: Int? = Int(txtShowers.text!)
        if bath != nil {
            success = success + 1
        } else if bath == nil {
            
            lblBathError.text = ("Please input a valid number")
        }
        
        let dishwasher: Int? = Int(txtShowers.text!)
        if dishwasher != nil {
            
            success = success + 1
        } else if dishwasher == nil {
            lbldishwasherError.text = ("Please input a valid number")
            
        }
        
        let washingMachine: Int? = Int(txtShowers.text!)
        if washingMachine != nil {
            success = success + 1
            
            
        } else if washingMachine == nil {
            lblWashingMachineError.text = ("Please input a valid number")
        }
        
        let teethLength: Int? = Int(txtShowers.text!)
        if teethLength != nil {
            
            success = success + 1
        } else if teethLength == nil {
            lblTeethError.text = ("Please input a valid number")
            
        }
        
        let toiletFlushes: Int? = Int(txtShowers.text!)
        if toiletFlushes != nil {
            
            success = success + 1
        } else if toiletFlushes == nil {
            
            lblToiletError.text = ("Please input a valid number")
        }
        
        let numOfPeople: Int? = Int(txtShowers.text!)
        if numOfPeople != nil {
            
            success = success + 1
        } else if numOfPeople == nil {
            lblNumOfPeopleError.text = ("Please input a valid number")
        }
        
        
        if success == 7 {
            var totalSum = (shower! * 10)
            totalSum = totalSum + (bath! * 150)
            totalSum = totalSum + (dishwasher! * 30)
            totalSum = totalSum + (washingMachine! * 90)
            totalSum = totalSum + (teethLength! * 5)
            totalSum = totalSum + (numOfPeople! * 10)
            totalSum = totalSum + (toiletFlushes! * Int(4.5))
            lblTotalSum.text = ("Your average daily water use is \(totalSum)")
            
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        //Looks for single or multiple taps.
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self,action: #selector(self.dismissKeyboard))
        
        //Uncomment the line below if you want the tap not not interfere and cancel other interactions.
        //tap.cancelstouchesInView = false
        
        view.addGestureRecognizer(tap)
    }
    
    //Calls this function when the tap is recognized.
    @objc func dismissKeyboard() {
        //Causes the view (or one of its embedded text fields) to resign the first responder status.
        view.endEditing(true)
        
        
        
        // Do any additional setup after loading the view.
    }
    
    
    /*
     // MARK: - Navigation
     
     // In a storyboard-based application,you will often want to do a little preparation before navigation
     override func prepare(for segue: UIStoryboardSegue,sender: Any?) {
     // Get the new view controller using segue.destination.
     // Pass the selected object to the new view controller.
     }
     */
    
}

解决方法

问题可能是您正在尝试将nil值转换为Int。

在每种此类行中：-let shower: Int? = Int(txtShowers.text!)此处txtShowers.text可以为nil或任何其他类似的值，请尝试在此设置断点。

您可以尝试使用此方法，首先使用如下所示的guard let获得所有想要的值：-

guard let shower = txtShowers.text else {\\Show some error or what you want}

这还将减少您的代码数量或代码行。

然后您可以轻松地在shower上执行操作。

仅提供信息：-您永远不要在代码中使用forcecast总是尝试使用guard let或if let