Question

我无法将一些数据传递给另一个视图控制器。

我需要将注释的标题传递给我的第二个VC上的标签。

我不知道我到底哪里出错了，我整天都在摸不着头脑，试图解决它。

ViewController.swift

//Perform segue when callout has been tapped
func mapView(_ mapView: MKMapView, annotationView view: MKAnnotationView, calloutAccessoryControlTapped control: UIControl) {

  self.performSegue(withIdentifier: "showAnnotationInfo", sender:view)

   }

我目前正在尝试使用func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView)，但我收到的错误是：“在进行初始化之前使用”常量'destVC'。

在didSelect函数中，我能够在控制台中完美地显示所选的注释标题。

//Idenify when callout has been selected
 func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {

        print("Annotation selected")

        if let annotation = view.annotation as? POIAnnotations {

           let destVC : ShopDetailViewController?

            //error: constant 'destVC' used before being initialized
            destVC?.shopNameData = annotation.title!

            print("Your annotation title is: \(annotation.title!)");

        }

    }

func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showAnnotationInfo" {

      //I'm not sure what goes here. 

            }
        }

ShopDetailViewController.swift

一旦annotation.title传递给shopNameData，它就会传递给标签，如下所示。

var shopNameData = "thisDataMustChange"

    override func viewDidLoad() {
        super.viewDidLoad()

        self.shopName.text = self.shopNameData

        // Do any additional setup after loading the view.
    }

Answer 1

改为在prepareForSegue中设置shopNameData。

if segue.identifier == "showAnnotationInfo" {
    guard let annotationTitle = annotationTitle else {
        print("annotation title not set before segue to ShopDetailViewController.")
        return
    }
    guard let controller = segue.destination as? ShopDetailViewController else {
        print("improper controller for this segue")
        return
    }

    controller.shopNameData = annotationTitle
}

在地图上选择时设置annotationTitle的位置。见下文。

var annotationTitle = ""
func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {
  if let annotation = view.annotation as? POIAnnotations {
    annotationTitle = annotation.title!
  }
}

Answer 2

在SE上尝试一些类似的问题，我得出了这样的结论：

var annotationTitle = ""
func mapView(_ mapView: MGLMapView, annotation: MGLAnnotation, calloutAccessoryControlTapped control: UIControl) {
    // mapView.deselectAnnotation(annotation, animated: true) // Hide the callout view.
    annotationTitle = annotation.title!!
    performSegue(withIdentifier: "toDetail", sender: view)
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if (segue.identifier == "toDetail" ) {
        print("Segue toDetail")
        let annotationTitle = self.annotationTitle
        let theDestination = segue.destination as! StationController
        theDestination.LabelText = annotationTitle
    }
}

Swift：将注释标题传递给我的第二个视图控制器标签

2 个答案: