ios - 如何从 UILabel 中删除最后输入的数字？

Question

如果我在标签中输入数字，如果输入有误，如何从 UILabel 中删除最后输入的数字？

我已经放置了一个按钮，用于从标签中删除最后一位数字。

按钮的名称是返回。

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var lbltext: UILabel!
    @IBOutlet var scrolview1: UIScrollView!
    @IBOutlet var fi: UITextField!
    @IBOutlet var scrolviewus: UIScrollView!
    @IBOutlet var counterLabel: UILabel!
    var isFirstTime = true

    override func viewDidLoad() {
        super.viewDidLoad()
    }

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


    @IBAction func button(sender: AnyObject) {
        lbltext.numberOfLines = 0
        lbltext.text! = lbltext.text! + "\n" + fi.text! + "\n" + "---"
    }

    @IBAction func back(sender: AnyObject) {

    }
}

Answer 1

试试这个:

@IBAction func back(sender: AnyObject) {
    if let text = lbltext.text {
        lbltext.text = String(text.characters.dropLast())
    }
}

---

因为你想删除的不仅仅是最后添加的数字，所以在一个名为 previous 的属性中保留标签的先前状态，并在按下 back 时恢复它:

var previous = ""

@IBAction func button(sender: AnyObject) {
    lbltext.numberOfLines = 0
    previous = lbltext.text!
    lbltext.text! = lbltext.text! + "\n" + fi.text! + "\n" + "---"
}

@IBAction func back(sender: AnyObject) {
    if !previous.isEmpty {
        lbltext.text = previous
        previous = ""
    }
}

---

对于多级撤销，使用一个数组来保存你之前的标签:

var previous: [String] = []

@IBAction func button(sender: AnyObject) {
    lbltext.numberOfLines = 0
    previous.append(lbltext.text!)
    lbltext.text = lbltext.text! + "\n" + fi.text! + "\n" + "---"
}

@IBAction func back(sender: AnyObject) {
    if let last = previous.last {
        lbltext.text = last
        previous.removeLast()
    }
}