Question

Xcode返回错误，表示表视图无法从其数据源获取单元格。我正在使用搜索栏输入搜索字词，并将其显示在表格视图下方。

我的第一个想法是检查我是否已将单元格标识符设置为cell，这是正确的，但我认为此代码中可能还有其他内容。如果有必要，我可以添加其余的代码，但我只想先看看我是否遗漏了一些内容。

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("cell")!
        let selectedItem = searchedItems[indexPath.row].placemark
        cell.textLabel?.text = selectedItem.name
        cell.detailTextLabel?.text = ""
        return cell
    }
}

编辑以从两个视图控制器添加完整代码。到目前为止的目的是获得用户的位置，然后能够输入搜索词，例如，在搜索栏中定位目标，并在表格视图中显示搜索结果。

第一视图控制器

import UIKit
import MapKit
import CoreLocation

class ViewController: UIViewController {

    //this variable is for access to the location manager throughout the scope of the controller
    let locationManager = CLLocationManager()

    @IBOutlet weak var mapView: MKMapView!

    var resultSearchController:UISearchController? = nil

    override func viewDidLoad() {
        super.viewDidLoad()
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.requestWhenInUseAuthorization() //this triggers authorization alert - one time only
        locationManager.requestLocation() //triggers an also one time location request

        let locationSearchTable = storyboard!.instantiateViewController(withIdentifier: "LocationSearchTable") as! LocationSearchTable
        resultSearchController = UISearchController(searchResultsController: locationSearchTable)
        resultSearchController?.searchResultsUpdater = locationSearchTable


        //configure the search bar and embed within the navigation bar
        let searchBar = resultSearchController!.searchBar
        searchBar.sizeToFit()
        searchBar.placeholder = "Search for places"
        navigationItem.titleView = resultSearchController?.searchBar

        //configure the UISearchController appearance
        resultSearchController?.hidesNavigationBarDuringPresentation = false //ensure search bar is accessible at all times
        resultSearchController?.dimsBackgroundDuringPresentation = true //for when search bar is selected
        definesPresentationContext = true

        locationSearchTable.mapView = mapView //passes along a handle of the mapView from the main VC onto the locationSearchTable

    }

}

//extension used for code organization to group delegate methods

extension ViewController : CLLocationManagerDelegate {

    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        if status == .authorizedWhenInUse { //is user responded with allow
            locationManager.requestLocation() //essentially requesting on the double as first is a permission failure before allow is pressed
        }
    }

    //gets called when location information comes back. You get an array of locations but only interested in first item. Eventually will zoom to this location
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

        if let location = locations.first {
            let span = MKCoordinateSpanMake(0.05, 0.05) //span is the zoom level set at arbitrary level for now
            let region = MKCoordinateRegionMake(location.coordinate, span)
            //once you combine coordinate and span into a region you can zoom using setRegion(_:animated:)
            mapView.setRegion(region, animated: true)
        }
    }

    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        print("error:: (error)")
    }

}

第二视图控制器

import UIKit
import MapKit


class LocationSearchTable : UITableViewController {

    var matchingItems:[MKMapItem] = [] //for stashing search results for easy access
    var mapView: MKMapView? = nil //search queries rely on map region for local results. This is ahandle to the map from the previous screen



    //this method converts the placemark to a custom address format like: "4 Melrose Place, Washington DC"

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


}

Answer 1

两件事。

确保您已分配正确的数据源。
确保您在数据源中说过它是UITableView的数据源。它符合UITableViewDataSource

YourViewController : UITableViewDataSource

无法从数据源获取单元格？

1 个答案: