Ios 在Swift中使用UISlider以编程方式更改UILabel

我正在学习Swift，并尝试使用滑块以编程方式更改标签值。我在func中得到一个错误，说paybackLabel是一个未解析的标识符。如何做到这一点

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        //Create Label
        let paybackLabel = UILabel(frame: CGRectMake(0, 0, 300, 41))
        paybackLabel.center = CGPointMake(190, 284)
        paybackLabel.textAlignment = NSTextAlignment.Center
        paybackLabel.font = UIFont(name: paybackLabel.font.fontName, size: 40)
        paybackLabel.textColor = UIColor.whiteColor()
        paybackLabel.text = "Hello World"
        self.view.addSubview(paybackLabel)

        //Create Slider
        let paybackSlider = UISlider(frame: CGRectMake (45,546,310,31))
        paybackSlider.minimumValue = 0
        paybackSlider.maximumValue = 1000
        paybackSlider.continuous = true
        paybackSlider.tintColor = UIColor.blueColor()
        paybackSlider.value = 500
        paybackSlider.addTarget(self, action: "paybackSliderValueDidChange:",forControlEvents: .ValueChanged)

        self.view.addSubview(paybackSlider)

    }

    func paybackSliderValueDidChange(sender: UISlider!)
    {
        print("payback value: \(sender.value)")
        paybackLabel.text = "\(sender.value)"

    }


}

---

在ViewDidLoad（）之外全局声明

另外，不要忘记将userInteractionEnabled设置为true

   paybackLabel.userInteractionEnabled = true
    paybackSlider.userInteractionEnabled = true

---

请按照我在这里的建议更正代码

1.）为外部定义两个变量，以便公开访问和修改标签值

var paybackLabel : UILabel = UILabel()
var paybackSlider : UISlider = UISlider()

2.）将下面的代码放入viewDidload（）中

3.）不放置通过更改slidervaluechanged事件来更改标签上显示值的函数

func paybackSliderValueDidChange(sender: UISlider!)
{
    print("payback value: \(sender.value)")
    paybackLabel.text = "\(sender.value)"
}

结果:

---

现在它的工作很好享受..

是的，事实上代码不应该编译。你必须将viewDidLoad外部的paybackLabel声明为var，并在viewDidLoad中修改它，然后更改PaybackSliderValueDidChange中的文本请检查我给出的答案。如果它的工作正确，请接受我的答案并投票。谢谢。userInteractionEnabled做什么？似乎标签和滑块在没有它的情况下可以工作。另外，为什么要将var paybackSlider声明为全局变量？似乎没有它也行。

//Create Label

paybackLabel = UILabel(frame: CGRectMake(10, 20, 100, 41))
paybackLabel.center = CGPointMake(190, 61)
paybackLabel.textAlignment = NSTextAlignment.Center
paybackLabel.font = UIFont(name: paybackLabel.font.fontName, size:10)
paybackLabel.textColor = UIColor.blueColor()
paybackLabel.text = "Hello World"
self.view.addSubview(paybackLabel)

//Create Slider

paybackSlider = UISlider(frame: CGRectMake (45,70,310,31))
paybackSlider.minimumValue = 0
paybackSlider.maximumValue = 1000
paybackSlider.continuous = true
paybackSlider.tintColor = UIColor.blueColor()
paybackSlider.value = 500
paybackSlider.addTarget(self, action: "paybackSliderValueDidChange:",forControlEvents: .ValueChanged)
paybackLabel.text = "\(paybackSlider.value)"
self.view.addSubview(paybackSlider)

func paybackSliderValueDidChange(sender: UISlider!)
{
    print("payback value: \(sender.value)")
    paybackLabel.text = "\(sender.value)"
}