应用程序崩溃尝试在视图控制器和tableviewcontroller之间传递数据

Question

所以我有一个导航控制器，它包含一个视图控制器和一个UITableViewController。视图控制器包含mapview和textfield，tableviewcontroller搜索位置。

当我在表格视图控制器中选择一个位置时，我希望能够将该地址存储在文本字段中。我可以得到我想要打印的地址

然而，每当我尝试将该地址分配给文本字段时，应用程序崩溃时出现“致命错误：在展开可选值时意外发现nil”有人知道原因吗？这是我的tableview控制器代码：

import UIKit
import MapKit

class LocationSearchTable: UITableViewController {


    weak var handleMapSearchDelegate: HandleMapSearch?
    var matchingItems: [MKMapItem] = []
    var mapView: MKMapView?


    func parseAddress(_ selectedItem:MKPlacemark) -> String {

        // put a space between "4" and "Melrose Place"
        let firstSpace = (selectedItem.subThoroughfare != nil &&
                            selectedItem.thoroughfare != nil) ? " " : ""

        // put a comma between street and city/state
        let comma = (selectedItem.subThoroughfare != nil || selectedItem.thoroughfare != nil) &&
                    (selectedItem.subAdministrativeArea != nil || selectedItem.administrativeArea != nil) ? ", " : ""

        // put a space between "Washington" and "DC"
        let secondSpace = (selectedItem.subAdministrativeArea != nil &&
                            selectedItem.administrativeArea != nil) ? " " : ""

        let addressLine = String(
            format:"%@%@%@%@%@%@%@",
            // street number
            selectedItem.subThoroughfare ?? "",
            firstSpace,
            // street name
            selectedItem.thoroughfare ?? "",
            comma,
            // city
            selectedItem.locality ?? "",
            secondSpace,
            // state
            selectedItem.administrativeArea ?? ""


        )

        return addressLine
    }



}

extension LocationSearchTable : UISearchResultsUpdating {

    func updateSearchResults(for searchController: UISearchController) {
        guard let mapView = mapView,
            let searchBarText = searchController.searchBar.text else { return }

        let request = MKLocalSearchRequest()
        request.naturalLanguageQuery = searchBarText
        request.region = mapView.region
        let search = MKLocalSearch(request: request)

        search.start { response, _ in
            guard let response = response else {
                return
            }
            self.matchingItems = response.mapItems
            self.tableView.reloadData()


        }

    }

}

extension LocationSearchTable {

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return matchingItems.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell")!
        let selectedItem = matchingItems[indexPath.row].placemark
        cell.textLabel?.text = selectedItem.name
        cell.detailTextLabel?.text = parseAddress(selectedItem)

       // let right = (cell.detailTextLabel?.text)!

       // print(right)

        //print(selectedItem.name)
      //  print(parseAddress(selectedItem))

        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let selectedItem = matchingItems[indexPath.row].placemark
        handleMapSearchDelegate?.dropPinZoomIn(selectedItem)
        dismiss(animated: true, completion: nil)

         let cell = tableView.dequeueReusableCell(withIdentifier: "cell")!


         cell.detailTextLabel?.text = parseAddress(selectedItem)






        DispatchQueue.main.async {
        let right = cell.detailTextLabel?.text
        print (right!)
        let vc = ViewController()
        vc.testTxt.text = right!

        }


}
}

Answer 1

您不应该在cell = tableView.dequeueReusableCell(withIdentifier: "cell")!方法中执行此操作didSelectRow。如果你想看看哪个项目被选中，你需要通过indexPath.row从数组中获取它作为这样的索引

verride func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let selectedItem = matchingItems[indexPath.row].placemark
}

要将此数据传递给上一个视图控制器，您需要一个展开segue like this post。

Answer 2

在<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/colorPrimary" android:minHeight="?attr/actionBarSize" app:popupTheme="@style/ThemeOverlay.AppCompat.Light" android:theme="@style/ThemeOverlay.AppCompat.Dark" app:titleTextColor="@android:color/white" app:contentInsetStartWithNavigation="0dp"> </android.support.v7.widget.Toolbar> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:text="Price:" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center|bottom" android:textStyle="bold" android:textColor="@color/colorPrimary" android:paddingLeft="2dp" android:layout_margin="5dp"/> <TextView android:text="block" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center|bottom" android:textStyle="bold" android:textColor="@color/colorPrimary" android:paddingLeft="2dp" android:layout_margin="5dp"/> <TextView android:text="floor" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center|bottom" android:textStyle="bold" android:textColor="@color/colorPrimary" android:paddingLeft="2dp" android:layout_margin="5dp"/> <LinearLayout android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="5"> <Button android:id="@+id/button01" android:text="button" android:layout_width="match_parent" android:layout_height="wrap_content" android:textStyle="bold" android:layout_gravity="bottom" android:textColor="@android:color/white" /> </LinearLayout> </LinearLayout> 的扩展程序中，您正在解除控制器，然后尝试将单元格出列。由于控制器不再存在，我认为tableView为零，didSelectRow导致崩溃。您可能想要做的是dequeueing pushing您应该在当前TableViewController的引用中传递，然后使用它来设置controller属性

textfield