ios - 尝试从文本字段获取纬度和经度时无法转换类型的值

Question

Image of the project

我的代码不工作。当用户输入纬度和经度时，它应该转到 map ，但它只是抛出一个错误。它仅在我对纬度和经度进行硬编码时有效。

import UIKit
import MapKit

class ViewController: UIViewController {
    @IBOutlet weak var Longitude: UITextField!
    @IBOutlet weak var Latitude_button: UITextField!

    @IBAction func showMeWhere(_ sender: Any)
    {
        //Defining destination
        let latitude:CLLocationDegrees = Latitude_button
        let longitude:CLLocationDegrees = Longitude

      //        let latitude:CLLocationDegrees = 39.048825
    //        let longitude:CLLocationDegrees = -120.981227

        let regionDistance:CLLocationDistance = 1000;
        let coordinates = CLLocationCoordinate2DMake(latitude, longitude)
        let regionSpan = MKCoordinateRegionMakeWithDistance(coordinates, regionDistance, regionDistance)

        let options = [MKLaunchOptionsMapCenterKey: NSValue(mkCoordinate: regionSpan.center), MKLaunchOptionsMapSpanKey: NSValue(mkCoordinateSpan: regionSpan.span)]

        let placemark = MKPlacemark(coordinate: coordinates)
        let mapItem = MKMapItem(placemark: placemark)
        mapItem.name = "Test Location"
        mapItem.openInMaps(launchOptions: options)
    }
}

Answer 1

在您的 let latitude:CLLocationDegrees = Latitude_button 行中，您试图将类型为 UITextField 的变量分配给类型为 CLLocationDegrees 的变量。

您需要做的是从文本字段中获取文本并尝试将其转换为数字，然后将该数字分配给您的变量。

guard let latitude = CLLocationDegrees(Latitude_button.text!),
      let longitude = CLLocationDegrees(Longitude.text!) else {
    // show some sort message to the user that the values are invalid
    return
}