小编Jam*_*mes的帖子

我正在学习Swift并尝试使用Slider以编程方式更改Label值.我在func中收到错误,说paybackLabel是一个未解析的标识符.该怎么做？

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 …