iOS Swift-协议将委托发送到错误的TableViewController

Question

I have an app with a chain of TableViewControllers, linked by a notification controller, retrieving information from a webservice. Data from the next table is pulled from an webservice, regarding the data chosen on the previous one. When I pull any table to refresh, it requests again the information a protocol sends a delegate message to the tableview to refresh the information.

Well, so far so good. But, I'm experiencing something strange... Example: I'm on tableView #2 and then use the navigation back button to get to the previous table, the #1. When, on #1, I pull the tableview to refresh, it crashes and gives me one of those "unrecognized selector sent to instance" telling that Tableview #2 doesn't have the optional delegate method, used to get the information to fill TableView #1. And I'm not even on TableView #2 anymore, iOS is sending the delegate message to the wrong ViewController, as the tableViewController wasn't even dismissed when the NavigationController backButton was clicked...

Has anyone experienced it? I know it seems a little bit confuse, but it is what's happening.

Lets get some code in here: Two TableViewControllers: ClientsViewController and ProjectsViewController When you select a client on the ClientsViewController Table, it loads all projects from the client on the ProjectsViewController Table.

ClientsViewController

override func viewDidLoad() {
        super.viewDidLoad()
        wsCommHandler.delegate = self
        self.tableView.delegate = self
        self.tableView.dataSource = self

        self.refreshControl!.addTarget(self, action: Selector("refreshClients:"), forControlEvents: UIControlEvents.ValueChanged)
        wsCommHandler.getClients()

    }

    func refreshClients(sender:AnyObject){
        println("Refreshing")
        self.refreshControl?.beginRefreshing()
        wsCommHandler.getClients()
        self.refreshControl?.endRefreshing()
    }

func didReceiceResponseFromGetClientsRequest(response: [AnyObject]) {
        self.clients = response
        self.tableView.reloadData()

    }

The wsCommHandler 'getClients()' retrieves from a webservice all the clients and uses a delegate 'didReceiceResponseFromGetClientsRequest' to reload the table.

When a client is selected it segues to the next TableViewController, passing a client_id between the ViewControllers.

Here's a code sample from the ProjectsViewController

override func viewDidLoad() {
        super.viewDidLoad()
        wsCommHandler.delegate = self
        self.tableView.delegate = self
        self.tableView.dataSource = self

        self.refreshControl!.addTarget(self, action: Selector("refreshProjects:"), forControlEvents: UIControlEvents.ValueChanged)
        wsCommHandler.getProjectsByClient(client_id) 
    }

    func refreshProjects(sender:AnyObject){
        println("Refreshing")
        self.refreshControl?.beginRefreshing()
        wsCommHandler.getProjectsByClient(client_id)
        self.refreshControl?.endRefreshing()
    }

    func didReceiceResponseFromGetProjectsRequest(response: [AnyObject]) {
        self.projects = response
        self.tableView.reloadData()

    }

It loads the Projects on the screen on the same way as the clients, but now using the delegate 'didReceiceResponseFromGetProjectsRequest'

Now, if I press the navigation controller back button, it brings the ClientsViewController back to front (without reloading it)... When I pull it to refresh. The class is called, retrieves the data and then: Crash!

2015-03-06 09:26:18.978 PostItHours[9174:792018] -[PostItHours.ProjectsViewController didReceiceResponseFromGetClientsRequest:]: unrecognized selector sent to instance 0x7fe0c4132c30 2015-03-06 09:26:18.980 PostItHours[9174:792018] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[PostItHours.ProjectsViewController didReceiceResponseFromGetClientsRequest:]: unrecognized selector sent to instance 0x7fe0c4132c30'

As you guys can see, it is trying to do it on the ProjectsViewController, which was already dismissed, by the backButton.

Any ideas?

Answer 1

I tried and it works for me. 2 viewcontrollers, each with a different data source, a "toSecondVC" segue between the two.

The ViewController :

import UIKit

class ViewController: UITableViewController {
    var texts = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()
        texts.append("viewController")
        self.title = "viewController"
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        refreshControl = UIRefreshControl()
        refreshControl!.addTarget(self,
            action: "handleRefresh:",
            forControlEvents: .ValueChanged)

        tableView.addSubview(refreshControl!)

    }

    func handleRefresh(paramSender: AnyObject){
        //pause it 1 sec
        let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(NSEC_PER_SEC))
        dispatch_after(popTime,
            dispatch_get_main_queue(), {
                self.texts.append(String("viewController-\(self.texts.count+1)"))
                self.refreshControl!.endRefreshing()
                let indexPathOfNewRow = NSIndexPath(forRow: self.texts.count - 1,
                    inSection: 0)

                self.tableView!.insertRowsAtIndexPaths([indexPathOfNewRow],
                    withRowAnimation: .Automatic)
        })
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "toSecondVC" {
            let viewController:SecondVC = segue.destinationViewController as SecondVC
            let indexPath = self.tableView.indexPathForSelectedRow()
            viewController.stringSelected = texts[indexPath!.row]
        }
    }

    //MARK : TableView Delegate
    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
        cell.textLabel.text = texts[indexPath.row]
        return cell
    }

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

The secondVC :

import UIKit

class SecondVC: UITableViewController {
    var texts = [String]()
    var stringSelected = String()

    override func viewDidLoad() {
        super.viewDidLoad()
        self.title = "secondVC"
        texts.append("secondVC")
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        refreshControl = UIRefreshControl()
        refreshControl!.addTarget(self,
            action: "handleRefresh:",
            forControlEvents: .ValueChanged)

        tableView.addSubview(refreshControl!)

        println("stringSelected : \(stringSelected)")
    }

    func handleRefresh(paramSender: AnyObject){

        //pause it 1 sec
        let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(NSEC_PER_SEC))
        dispatch_after(popTime,
            dispatch_get_main_queue(), {
                self.texts.append(String("secondVC-\(self.texts.count+1)"))
                self.refreshControl!.endRefreshing()
                let indexPathOfNewRow = NSIndexPath(forRow: self.texts.count - 1,
                    inSection: 0)

                self.tableView!.insertRowsAtIndexPaths([indexPathOfNewRow],
                    withRowAnimation: .Automatic)

        })

    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
        cell.textLabel.text = texts[indexPath.row]
        return cell
    }

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


}