swift - prepareForSegue 中的函数不会执行

Question

我正在制作一个表格 View ，其中包含 channel ，用户可以点击该 channel 进入该 channel 。当用户点击该 channel 时，我想从 firebase 获取 channel 的 ID 和名称。下面的函数应该可以工作，但实际上没有。 prepare for segue 函数本身被执行，但 if let channel = sender as? Channel {//不执行 }.所以我没有看到“已执行”打印。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)
        if let channel = sender as? Channel {
        print("executed")
        let chatVc = segue.destination as! channelMultiplayerViewController
        chatVc.channel = channel
        chatVc.channelRef = channelRef.child(channel.id)
    }
}

如果您需要，这是我的完整代码:

import UIKit
import Firebase
import Foundation

enum Section: Int {
    case createNewChannelSection = 0
    case currentChannelsSection
}

extension multiplayerChannelView: UISearchResultsUpdating {
    func updateSearchResults(for searchController: UISearchController) {
        filterContentForSearchText(searchText: searchController.searchBar.text!)
    }
}

class multiplayerChannelView: UITableViewController {


    // MARK: Properties
    var channels: [Channel] = []
    let searchController = UISearchController(searchResultsController: nil)
    var filteredChannels = [Channel]()
    private lazy var channelRef: FIRDatabaseReference = FIRDatabase.database().reference().child("channels")
    private var channelRefHandle: FIRDatabaseHandle?
    var senderDisplayName: String?
    var newChannelTextField: UITextField?


    override func viewDidLoad() {
        super.viewDidLoad()
        title = "Rooms"
        observeChannels()
        searchController.searchResultsUpdater = self
        searchController.dimsBackgroundDuringPresentation = false
        definesPresentationContext = true
        tableView.tableHeaderView = searchController.searchBar
    }
    deinit {
        if let refHandle = channelRefHandle {
            channelRef.removeObserver(withHandle: refHandle)
        }
    }
    func filterContentForSearchText(searchText: String, scope: String = "All") {
        filteredChannels = channels.filter { Channel in
            return (Channel.name.lowercased().range(of: searchText.lowercased()) != nil)
        }

        tableView.reloadData()
    }
    @IBAction func createChannel(_ sender: AnyObject) {
        if let name = newChannelTextField?.text {
            let newChannelRef = channelRef.childByAutoId()
            let channelItem = [
                "name": name
            ]
            newChannelRef.setValue(channelItem)
        }
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    }
    private func observeChannels() {
        channelRefHandle = channelRef.observe(.childAdded, with: { (snapshot) -> Void in // 1
            let channelData = snapshot.value as! Dictionary<String, AnyObject> // 2
            let id = snapshot.key
            if let name = channelData["name"] as! String!, name.characters.count > 0 {
                self.channels.append(Channel(id, name: name))
                self.tableView.reloadData()
            } else {
                print("Error! Could not decode channel data")
            }
        })
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 2
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if let currentSection: Section = Section(rawValue: section) {
            switch currentSection {
            case .createNewChannelSection:
                return 1

            case .currentChannelsSection:
                if searchController.isActive && searchController.searchBar.text != "" {
                    return filteredChannels.count
                }
                else{
                    return channels.count
                }
            }
        } else {
            return 0
        }
    }
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let reuseIdentifier = (indexPath as NSIndexPath).section == Section.createNewChannelSection.rawValue ? "NewChannel" : "ExistingChannel"
        let cell = tableView.dequeueReusableCell(withIdentifier: reuseIdentifier, for: indexPath)

        if (indexPath as NSIndexPath).section == Section.createNewChannelSection.rawValue {
            if let createNewChannelCell = cell as? CreateChannelCell {
                newChannelTextField = createNewChannelCell.newChannelNameField
            }
        } else if (indexPath as NSIndexPath).section == Section.currentChannelsSection.rawValue {
            if searchController.isActive && searchController.searchBar.text != "" {
                cell.textLabel?.text = filteredChannels[(indexPath as NSIndexPath).row].name
            } else {
                cell.textLabel?.text = channels[(indexPath as NSIndexPath).row].name
            }
        }

        return cell
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        super.prepare(for: segue, sender: sender)
            if let channel = sender as? Channel {
            print("executed")
            let chatVc = segue.destination as! channelMultiplayerViewController
            chatVc.channel = channel
            chatVc.channelRef = channelRef.child(channel.id)
        }
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        if indexPath.section == Section.currentChannelsSection.rawValue {
            var channel = channels
            if searchController.isActive && searchController.searchBar.text != "" {
                channel = [filteredChannels[(indexPath as NSIndexPath).row]]
                     }
            else
            {
                channel = [channels[(indexPath as NSIndexPath).row]]
            }

            self.performSegue(withIdentifier: "ShowChannel", sender: channel)
        }
    }

}

这是一个 Channel 类型的 .swift 文件

import Foundation

class Channel: NSObject {
    let id:String
    let name:String
    init (_ id:String, name:String){
        self.id = id
        self.name = name
    }
}

谢谢!

Answer 1

我也回复了你的上一篇文章，但你发送了一系列 channel 到

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)
        if let channel = sender as? Channel {
        print("executed")
        let chatVc = segue.destination as! channelMultiplayerViewController
        chatVc.channel = channel
        chatVc.channelRef = channelRef.child(channel.id)
    }
}

所以 block - 如果让 channel = 发件人作为？ channel - 将不起作用。

将单元格选择代码更改为:

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    if indexPath.section == Section.currentChannelsSection.rawValue {
        if searchController.isActive && searchController.searchBar.text != "" {
            let channel = filteredChannels[indexPath.row]
            self.performSegue(withIdentifier: "ShowChannel", sender: channel)
                 }
        else
        {
            let channel = channels[indexPath.row]
            self.performSegue(withIdentifier: "ShowChannel", sender: channel)
        }
    }
}