Question

我遇到了这段代码的问题，快速学习，我无法理解为什么。

我想要做的是用户输入两个TextField两个数字，单击一个Button，然后在Label上获得结果。

我知道TextField不允许使用Int，但只允许使用字符串，我知道有将字符串转换为Int的方法，但它对我不起作用。

以下是代码：

import UIKit

class ViewController: UIViewController {


    @IBOutlet weak var firstNumber: UITextField!
    @IBOutlet weak var secondNumber: UITextField!
    @IBOutlet weak var resultButton: UIButton!
    @IBOutlet weak var resultNumber: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.


    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    var firstNumberConv :Int? = Int(firstNumber.text)
    var secondNumberConv :Int? = Int(secondNumber.text)
    var result = firstNumberConv + secondNumberConv

    @IBAction func resultFunction(_ sender: AnyObject) {
        resultNumber.text = result

    }

}

Answer 1

为什么不把你的代码放在你的行动中

类似这样的事情

@IBAction func resultFunction(_ sender: AnyObject) {
    let firstNumberConv :Int? = Int(firstNumber.text!)
    let secondNumberConv :Int? = Int(secondNumber.text!)
    let result = firstNumberConv! + secondNumberConv!
    resultNumber.text = String(result)

}

我希望这有助于你

Answer 2

请尝试以下代码：

class ViewController: UIViewController {


    @IBOutlet weak var firstNumber: UITextField!
    @IBOutlet weak var secondNumber: UITextField!
    @IBOutlet weak var resultButton: UIButton!
    @IBOutlet weak var resultNumber: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func resultFunction(_ sender: AnyObject) {

        let firstNumberConv :Int? = Int(firstNumber.text!)
        let secondNumberConv :Int? = Int(secondNumber.text!)
        let result = firstNumberConv! + secondNumberConv!

        resultNumber.text =  String(result)

    }

}

Answer 3

首先，必须将代码放入函数中。

其次，要保持一致！

您使用数字键盘然后去打开选项：

@IBAction func resultFunction(_ sender: AnyObject) {
   let firstNumberConv = Int(firstNumber.text)!
   let secondNumberConv = Int(secondNumber.text)!
   resultNumber.text = "\(firstNumberConv + secondNumberConv)"
}

或者您正在使用标准键盘，然后使用可选绑定来检查用户是否键入了非数字字符：

@IBAction func resultFunction(_ sender: AnyObject) {
   if let firstNumberConv = Int(firstNumber.text), 
      let secondNumberConv = Int(secondNumber.text) {
        resultNumber.text = "\(firstNumberConv + secondNumberConv)"
   }
}

Answer 4

变量用法中的简单误解。变量“result”在ViewController对象启动时估算，而不是在调用“resultFunction”时估算。

所以你可以按照以下方式更正

@IBAction func resultFunction(_ sender: AnyObject) {
    let firstNumberConv = Int(firstNumber.text) ?? 0
    let secondNumberConv = Int(secondNumber.text) ?? 0
    let result = firstNumberConv + secondNumberConv
    resultNumber.text = "\(result)"
}

您应该删除所有变量定义部分。我的意思是这部分

var firstNumberConv :Int? = Int(firstNumber.text)
var secondNumberConv :Int? = Int(secondNumber.text)
var result = firstNumberConv + secondNumberConv

希望它能为你效劳。感谢

Answer 5

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var firstNumber: UITextField!
@IBOutlet weak var secondNumber: UITextField!
@IBOutlet weak var resultButton: UIButton!
@IBOutlet weak var resultNumber: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
  }

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }

var firstNumberConv :Int? = Int(firstNumber.text)
var secondNumberConv :Int? = Int(secondNumber.text)
var result = firstNumberConv + secondNumberConv

@IBAction func resultFunction(_ sender: AnyObject) {
    resultNumber.text = result

    }

  }

将您的代码放入viewDidLoad（）方法中，或者在下面执行此操作会更好

  func updateNumber(){

  let firstNumberConv = Int(firstNumber.text!)
  let secondNumberConv = Int(secondNumber.text!)
  let result = firstNumberConv! + secondNumberConv!
  resultNumber.text = String(result!)

  }

然后调用您的方法

@IBAction func resultFunction(_ sender: AnyObject) {
    updateNumber();
}

或者，如果您想转换为Double，只需更改

      Int(firstNumber.text!) to Double(firstNumber.text!)

在Int或Double中转换UITextField

5 个答案: