使用Swift将字符串转换为Int

Question

该应用程序基本上通过输入初始速度和最终速度以及时间来计算加速度，然后使用公式来计算加速度。但是，由于文本框中的值是字符串，所以我无法将它们转换为整数。

@IBOutlet var txtBox1 : UITextField
@IBOutlet var txtBox2 : UITextField
@IBOutlet var txtBox3 : UITextField
@IBOutlet var lblAnswer : UILabel


@IBAction func btn1(sender : AnyObject) {

    let answer1 = "The acceleration is"
    var answer2 = txtBox1
    var answer3 = txtBox2
    var answer4 = txtBox3

Answer 1

基本概念， 请注意，这仅在Swift 1.x中有效

    // toInt returns optional that's why we used a:Int?
    let a:Int? = firstText.text.toInt() // firstText is UITextField
    let b:Int? = secondText.text.toInt() // secondText is UITextField

    // check a and b before unwrapping using !
    if a && b {
        var ans = a! + b!
        answerLabel.text = "Answer is \(ans)" // answerLabel ie UILabel
    } else {
        answerLabel.text = "Input values are not numeric"
    }

Swift 4更新

...
let a:Int? = Int(firstText.text) // firstText is UITextField
let b:Int? = Int(secondText.text) // secondText is UITextField
...