NavigationController不会从函数调用+ swift推送

Question

I am basically trying to recreate whatsapp. My MainVC has a TableView that shows all current conversations and has a push segue to the ChatVC to display the entire conversation.

When a user wants to start a new conversation they click the button on the top right corner and the UserListVC comes from the bottom and displays a list of users.

My thinking here is that when a user clicks a user the "UsersListVC" dismisses (showing the mainVC) and calls a function to open up the ChatVC. However I havent been able call a function successfully after this dimiss from MainVC.

Please not right now I am not pushing any data through I just want to get the segues working correctly

MainVC.swift

func showChatVC() {

    print("FUnction called")
    let showChat = ChatVC()
    navigationController?.pushViewController(showChat, animated: false)

}

UsersListVC.swift

       func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            dismiss(animated: true) { 
                MainVC().showChatVC()
            }
        }

I have tried a few different variations and I cant seem to call the function in MainVC at all. Am I being too stubborn with my thinking doing the segues this way? Should I have a direct segue from UsersListVC to ChatVC

Answer 1

Try Below Code

Step - 1

• set up the storyboard identifiers .

• then try below code

  MainVC.swift

    func showChatVC() { let showChat = self.storyboard!.instantiateViewControllerWithIdentifier("ChatVc_ID") as! ChatVC self.navigationController?.pushViewController(showChat, animated: false) } 

UsersListVC.swift

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    dismiss(animated: true) { 
   let mainVC = self.storyboard!.instantiateViewControllerWithIdentifier("MainVC_ID") as! MainVC 
   mainVC.showChatVC()
         }
}

Answer 2

lots of answers here, thought I should add my go to solution for these types of problems, using a delegate pattern.

With a delegate you can call a function in MainVC from UsersListVC, this makes it much easier to segue to ChatVC and will also help when you are passing the selected user to ChatVC.

To make a delegate pattern you:

1. create a protocol which specifies the function your delegate class must implement, typically I do this above the delegate class, so MainVC.

    protocol UsersListDelegate: class { func newConversationCreated(withUser user: AnyObject) } 

---

2. have your delegate class (MainVC) conform to the protocol and implement the required function

    class MainVC: UIViewController, UsersListDelegate { func newConversationCreated(withUser user: AnyObject) { //I'll fill this in later in my answer } } 

---

3. create a variable in UsersListVC to hold the delegate class in

    class UsersListVC: UIViewController { weak var delegate: UsersListDelegate! } 

---

4. when you present UsersList from MainVC set the delegate variable to MainVC (self), for example if you segue to UsersList then this can be done in prepare for segue.

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if let destination = segue.destination as? UsersListVC { destination.delegate = self } } 

   or if you present it without a segue:

    func presentUsersList() { let userListsVC = UsersListVC() userListsVC.delegate = self self.present(userListsVC, animated: true) } 

---

Your delegate pattern is finished now. To call the delegate function when you want to create the new conversation and dismiss UserListsVC, you do it like this

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        delegate.newConversationCreated(withUser: /*Your User Object*/)

    }

And in MainVC you can implement the newConversationCreated function to:

• Dismiss UserLists
• Create ChatVC
• Pass on the user to ChatVC
• Present ChatVC

eg

    func newConversationCreated(withUser user: AnyObject) {

        dismiss(animated: true) { 

            let showChat = ChatVC()
            showChat.user = user
            navigationController?.pushViewController(showChat, animated: false)

        }

    }

---

ps It may seem weird to call dismiss from MainVC, but this is actually best practice according to apple (see the answer in this question for why). It will dismiss UserLists don't worry.

Answer 3

Try to send action from your tableView's didSelectRow method like

UIApplication.sharedApplication().sendAction("showChatVC", to: nil, from: nil, forEvent: nil)

Hope this helps.

Answer 4

I would recommend using the NotificationCenter :

In MainVC register for NewChatCreateNotification like:

NotificationCenter.default.addObserver(self, selector: #selector(autoNavigateToNewChat(_:)), name: NSNotification.Name(rawValue: "NewChatCreateNotification"), object: nil)

Still in MainVC , in the autoNavigateToNewChat: method, push ChatVC

Then post your notification after you dismiss UsersListVC

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    //Use this dict to populate the userInfo of the notification, then you can use it when you push to ChatVC. 
    //You can obviously add more info to it like userId etc. as long as the data conforms to: [AnyHashable: Any]
    let dict = ["chatId" as NSString : <the selected chatId> as NSNumber]

    dismiss(animated: true) { 
        NotificationCenter.default.post(name: Notification.Name(rawValue: "NewChatCreatedNotification"), object: self, userInfo: dict as [AnyHashable: Any])
    }
}

Answer 5

The following should work with your storyboard setup. Make sure to set the segue identifiers in the storyboard. I am using a button instead of table view cell in the UsersListVC .

import Foundation
import UIKit

internal enum SegueIdentifier: String {
    case showChat = "showChat"
    case showUserList = "showUserList"
}

internal final class MainVC: UIViewController {

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == SegueIdentifier.showUserList.rawValue, let vc = segue.destination as? UsersListVC {
            vc.completion = {
                [weak self] in self?.performSegue(withIdentifier: SegueIdentifier.showChat.rawValue, sender: nil)
            }
        }
    }
}

internal final class ChatVC: UIViewController {

}

internal final class UsersListVC: UIViewController {

    internal var completion: (() -> ())? = nil

    @IBAction func close(_ sender: UIButton) {
        dismiss(animated: true) {
            [weak self] in self?.completion?()
        }
    }
}

Answer 6

If I'm not mistaken, you create a new instance of MainVC in your dismiss closure.

dismiss(animated: true) { 
    MainVC().showChatVC()
}

Since this new ViewController is never shown on screen, it also cannot show another ViewController.

Try getting a reference to your existing MainVC .

dismiss(animated: true) { [weak self] in
    if let mainVC = self?.presentingViewController as? MainVC {
        self?.mainVC.showChatVC()
    }
}

Otherwise try using the Notification approach.