swift - 错误: Expression pattern of type 'CountableClosedRange' cannot match values of type 'UITextField!'

Question

当我在 Swift 中构建并运行此代码时，出现上述错误。我正在尝试这样做，以便用户可以输入一个数字，并且 switch 语句将返回与该数字对应的以下打印内容。

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var numberInput: UITextField!

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

    @IBAction func inputText(_ sender: Any) {

        switch numberInput {

        case 0 ... 50:
            print("Number is between 0 & 50")
        case 51 ... 100:
            print("Number is between 51 & 100")
        case 101 ... 150:
            print("Number is between 101 & 150")
        default:
            print("Fallback option")
        }
    }
}

Answer 1

您必须从文本字段中获取文本，它是字符串类型，而不是数字。您必须先将其转换为数字，然后在采用整数范围的 switch 语句中使用它。

guard let text = numberInput?.text,let number = Int(text) else { return }
switch number {

    case 0 ... 50:
        print("Number is between 0 & 50")
    case 51 ... 100:
        print("Number is between 51 & 100")
    case 101 ... 150:
        print("Number is between 101 & 150")
    default:
        print("Fallback option")
    }