Question

我创建了这个viewController：

import UIKit
import AVFoundation

class SelectClass: UIViewController, UITableViewDelegate, UITableViewDataSource  {

    @IBOutlet weak var tableView: UITableView!

    var list : [QCategoryy] = [QCategoryy]()
    var audioPlayer : AVAudioPlayer!
    var limit = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.delegate = self
        tableView.dataSource = self
        tableView.allowsMultipleSelection = true
        self.title = "Categories"
        list = NearbyPlaces.getCategories()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        list.sort() { $0.views > $1.views}
        tableView.reloadData()
    }

    @IBAction func doneTapp(_ sender: Any) {
        self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: nil)
    }

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

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let identifier = "CATEGORY_CELL"
        let cell = tableView.dequeueReusableCell(withIdentifier: identifier, for: indexPath)
        let selectedIndexPaths = tableView.indexPathsForSelectedRows
        let rowIsSelected = selectedIndexPaths != nil && selectedIndexPaths!.contains(indexPath)
       /* cell.accessoryType = rowIsSelected ? .checkmark : .none  */
        cell.accessoryType = list[indexPath.row].isSelected ? .checkmark : .none
        cell.textLabel?.text = list[indexPath.row].name
        return cell
    }

    let nearbySearchSegueIdentifier = "goToMcourse"

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let cell = tableView.cellForRow(at: indexPath)!
        cell.accessoryType = .checkmark

        /* self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: list[indexPath.row])  */
    }

    func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
        let cell = tableView.cellForRow(at: indexPath)!
        cell.accessoryType = .none
    }

    func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
        if let sr = tableView.indexPathsForSelectedRows {
            if sr.count == limit {
                let alertController = UIAlertController(title: "Oops", message:
                    "You are limited to \(limit) selections", preferredStyle: .alert)
                alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {action in }))
                self.present(alertController, animated: true, completion: nil)
                return nil
            }
        }

        return indexPath
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == nearbySearchSegueIdentifier {
            guard let category = sender as? QCategoryy else {
                return
            }
            if let selectedRows = tableView.indexPathsForSelectedRows {
                if let vc : CourseClass2 = segue.destination as? CourseClass2 {
                    vc.category = category

                }
            }
        }
    }
}

extension QCategoryy {
    private static let ketPrefix = "category-"

    var views:Int {
        get {
            return UserDefaults.standard.integer(forKey: QCategoryy.ketPrefix + name)
        }
    }

    func markView() {
        UserDefaults.standard.set(views + 1, forKey: QCategoryy.ketPrefix + name)
    }
}

其中有一个简单的tableView，我可以选择一行并转到下一个VC

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let cell = tableView.cellForRow(at: indexPath)!
    cell.accessoryType = .checkmark

    /* self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: list[indexPath.row])  */
}

使用此performSegue

/* self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: list[indexPath.row])  */

取决于之前按过的行，结果不同。现在我说你可以选择多个单元格然后继续在下一个VC中有一个按钮

@IBAction func doneTapp(_ sender: Any) 
    self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: nil)
}

要推，但只是不知道为什么，不考虑选定的行，所以当我点击按钮时它会将我发送到下一页，好像我没有选择任何行。问题的原因是什么？我该如何解决？

Answer 1

似乎问题很明显 - doneTap调用performSegue并将sender设置为nil：

@IBAction func doneTapp(_ sender: Any) {
    self.performSegue(withIdentifier: nearbySearchSegueIdentifier, sender: nil)
}

在prepareForSegue中，您在目标视图控制器上设置类别，但在此之前，您有一个guard语句，检查sender是否为选定类别。由于在这种情况下您已将sender设置为nil，因此该守护将导致代码跳过该类别的设置，并且您的代码行为就好像您还没有设置类别一样（因为你真的没有设置它。）

覆盖func prepare（对于segue：UIStoryboardSegue，sender：Any？）{

    if segue.identifier == nearbySearchSegueIdentifier {
        guard let category = sender as? QCategoryy else {
            return
        }
        if let selectedRows = tableView.indexPathsForSelectedRows {
            if let vc : CourseClass2 = segue.destination as? CourseClass2 {
                vc.category = category

            }
        }
    }
}

我的建议是删除guard，而是使用tableView.indexPathsForSelectedRows来确定要发送给下一个视图控制器的类别，并使用它们，例如：

// this will get you the list of selected categories, or if none is selected, an empty list
let selectedCategories: [QCategoryy] = tableView.indexPathsForSelectedRows?.map({ (indexPath) -> QCategoryy in
    return list[indexPath.row]
}) ?? []
vc.categories = selectedCategories

TableView排序项（Swift）

1 个答案: