swift - 在 Swift 中检查 Tip 和 PriceTxt 是否为空时不断出错

Question

输入 Tip 和 PriceTxt 的值时，我想先检查它是否为空，如果是则返回“添加数字”，但出现错误

线程 1：致命错误：在展开可选值时意外发现 nil

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var PriceTxt: UITextField!
    @IBOutlet weak var Tip: UITextField!
    @IBOutlet weak var totalFinal: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        totalFinal.text = ""
    }

    @IBAction func Calcualte(_ sender: Any) {
       if  (PriceTxt.text!) == nil || (Tip.text!) == nil
       {
           totalFinal.text = "Add numbers"
       }
       else {
          let price = Double(PriceTxt.text!)!
          let tipPer = Double(Tip.text!)!
          let TipMult =  price * (tipPer/100)
          let TipFinal = Double((round(100*TipMult)/100) + price)
          totalFinal.text = "$\(TipFinal)"
      }   
   }
}

标签： swiftnullcalculator