swift - 无法使用 swift 3 从其数据源获取单元格

Question

我将以下 UITableViewController 作为 searchResultsController 附加:

import UIKit
import MapKit

class LocationSearchTable : UITableViewController {
    var matchingItems:[MKMapItem] = []
    var mapView: MKMapView? = nil

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.dataSource = self
        tableView.delegate = self
    }
}

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 {
        print(matchingItems.count)
        return matchingItems.count
    }

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

例如，一旦 matchingItems.count 不等于 0，它就会崩溃:

0 0 10 2016-10-20 15:43:53.914 ios-App[9137:977735] * Assertion failure in -[UITableView _configureCellForDisplay:forIndexPath:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3599.6/UITableView.m:8035 2016-10-20 15:43:53.927 ios-App[9137:977735] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView (; layer = ; contentOffset: {0, -64}; contentSize: {768, 440}>) failed to obtain a cell from its dataSource

当我在 cellForRowAtIndexPath 中添加调试点时，它们从未到达，应用程序似乎在此点之前崩溃了？

Answer 1

错误

failed to obtain a cell from its dataSource

发生是因为cellForRowAtIndexPath的签名错误。在 Swift 3 中是

(override) func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell

并使用便捷的方法

let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for:indexPath)

它总是返回一个有效的非可选单元格。

---

PS:您不需要将数据源和委托(delegate)设置为 self，因为 UITableViewController 会隐式执行此操作