Ios 计算器swift2中的前导零

我的简单应用程序（计算器）中的前导零有问题。开始时，标签上会打印零，但当我点击按钮（例如“1”）时，我会看到“01”。看起来不太好，所以我想换一下。我的代码如下。有人能帮我吗

import UIKit

class ViewController: UIViewController {

var previousValue:Int?


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

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

//display
@IBOutlet weak var displayLabel: UILabel!

// buttons
@IBAction func buttonPressed(sender: AnyObject) {

   let numb = (sender as! UIButton).tag

    displayLabel.text = "\(displayLabel.text!)\(numb)"

}
//plus    
@IBAction func plusPress(sender: AnyObject) {
    previousValue = Int(displayLabel.text!)
    displayLabel.text = "+"

}
//minus    
@IBAction func minusPress(sender: AnyObject) {
    previousValue = Int(displayLabel.text!)
    displayLabel.text = "-"
}

// count
@IBAction func count(sender: AnyObject) {
    let result = previousValue! + Int(displayLabel.text!)!
    displayLabel.text = "\(result)"

}


@IBAction func clear(sender: AnyObject) {
    displayLabel.text=""
}

}

---

首先检查

displayLabel.text的内容。如果是
0
，则只需将
displayLabel.text
设置为按下的数字即可。此外，如果您在按下的
按钮中声明
发送者
，将其声明为
UIButton
，则不必强制转换：

@IBAction func buttonPressed(sender: UIButton) {
    let numb = sender.tag

    if displayLabel.text == "0" {
        displayLabel.text = "\(numb)"
    }
    else {
        displayLabel.text = "\(displayLabel.text!)\(numb)"
    }
}