ios - Swift 3 : How do I increase a variable being displayed as a UILabel, 然后以编程方式更新 UILabel？

Question

我有一个应该显示分数的标签，以及一个应该在每次按下时增加该分数的按钮。我的问题是无论我把函数放在哪里都会出错。

如果我在 viewDidLoad 类之上有一个函数，那么我会得到一个错误，因为它出现在我的标签之前，但是如果我把它放在 viewDidLoad 中的任何地方，我会得到一个错误，因为我不能调用本地函数，如果我把它之后的任何地方，然后我调用函数的按钮出现在函数之前。

我应该把这些东西放在哪里？有没有更好的方法一起做这一切？这本来应该如此简单......

import UIKit

class ViewController: UIViewController {

let phrase = "Your score: "
var increasingNum = 0

func scoreGoUp (sender: UIButton){

    increasingNum += 1
    label.text = "\(phrase) \(increasingNum)"

}

override func viewDidLoad() {
    super.viewDidLoad()

    let label = UILabel(frame: CGRect(x: self.view.frame.size.width / 2 - 100, y: self.view.frame.size.height / 2 - 10, width: 200, height: 20))
    label.textAlignment = .center
    label.text = "\(phrase) \(increasingNum)"
    self.view.addSubview(label)

    let button = UIButton(frame: CGRect(x: self.view.frame.size.width / 2 - 150, y: 100, width: 300, height: 50))
    button.backgroundColor = UIColor.cyan
    button.addTarget(self, action: #selector(scoreGoUp), for: .touchUpInside)
    self.view.addSubview(button)

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()

}

}

Answer 1

我已经修改了你的代码。希望对您有所帮助。

class ViewController: UIViewController {

var label:UILabel!
    let phrase = "Your score: "
    var increasingNum = 0


    override func viewDidLoad() {
        super.viewDidLoad()

        label = UILabel(frame: CGRect(x: self.view.frame.size.width / 2 - 100, y: self.view.frame.size.height / 2 - 10, width: 200, height: 20))
        label.textAlignment = .center
        label.text = "\(phrase) \(increasingNum)"
        self.view.addSubview(label)

        let button = UIButton(frame: CGRect(x: self.view.frame.size.width / 2 - 150, y: 100, width: 300, height: 50))
        button.backgroundColor = UIColor.cyan
        button.addTarget(self, action: #selector(scoreGoUp), for: .touchUpInside)

        self.view.addSubview(button)

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()

    }

    func scoreGoUp (sender: UIButton){

        increasingNum += 1
        label.text = "\(phrase) \(increasingNum)"

    }
}

Here is the output