Passing Data from ViewController to UITableViewController - ios

Question

Help me to understand what I am missing please?
Storyboard setup:
ViewController -> TabBarController -> NavigationController which contains a TableViewController
There is a segue with Identifier "startUp" from the ViewController to the TabBarController
The ViewController is the Initial Entry Screen.
The ViewController has a SegmentedControl and a Button
USAGE: User selects one of the segments and presses the button. The view should segue to the TableViewController and replace the NavigationItem.Title with the title from the SegmentedControl segment which was selected.
PROBLEM: The data is not being passed from the ViewController to the TableViewController (and through the TabBarController and NavigationController). I am always ending up with a blank Header Title on the TableViewController. I have walked carefully through a couple dozen 'how-tos' over the past few days both here and other locations on the web using segue and other methods. At this point nothing seems to work and I'm dizzy (and probably missing something really, really basic).
Here is the way the code currently 'sits'
ViewController Code:
import UIKit
class ViewController: UIViewController {
var someData: String? = ""
#IBOutlet weak var cpChoice: UISegmentedControl!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func startBut(_ sender: Any) {
performSegue(withIdentifier: "startUp", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let theIndex = cpChoice.selectedSegmentIndex
someData = cpChoice.titleForSegment(at: theIndex)
print(someData!) //outputs correctly to console
if segue.destination is CheckpointVC
{
let vc = segue.destination as? CheckpointVC
vc?.data = someData!
}
}
}
TableViewController Code:
import UIKit
class CheckpointVC: UITableViewController {
var data: String = ""
#IBOutlet weak var theHeader: UINavigationItem!
override func viewDidLoad() {
super.viewDidLoad()
self.navigationItem.title = data
//theHeader.title = data
}
override func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 0
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return 0
}
}

Answer 1

Did you breakpoint on the segue to actually check if segue.destination is CheckpointVC? The solution has been right in front of your eyes all along. Since you have setup the viewcontrollers as such...
ViewController -> TabBarController -> NavigationController which contains a TableViewController
Your segue.destination is technically TabBarController unless the segue with identifier startUp leads to TableViewVC.
A short way to solve it is to unwrap the TableVC from your TabBarVC as such:
(tabBarVC.viewControllers[indexOfYourNavVC] as? NavigationController).viewControllers.first as? TableVC)
The longer but cleaner way of doing it is to implement a routing pattern from this blog. Sorry to say that I myself am still learning about this so I can only recommend websites to start with:
https://clean-swift.com/routing-in-clean-swift/

Answer 2

Just replace the segue target to a Navigation Controller Which contain your CheckpointVC as a root view controller.

Answer 3

The solution
PIECE DEFINITIONS
ViewController.swift
import UIKit
class ViewController: UIViewController {
var someData: String? = ""
#IBOutlet weak var cpChoice: UISegmentedControl!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func startBut(_ sender: Any) {
performSegue(withIdentifier: "startUp", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
//get the string representing the segment chosen and assign it to someData
let theSegmentChosen = cpChoice.selectedSegmentIndex
someData = cpChoice.titleForSegment(at: theSegmentChosen)
let barVC = segue.destination as! UITabBarController //
let navigationControllerDestination = barVC.viewControllers?[0] as? navVC //the array index [0] indicates the first view controller belonging to the TabBarController
let firstViewControllerOfNavigationController = navigationControllerDestination?.topViewController as! CheckpointVC
firstViewControllerOfNavigationController.data = someData!
}
}
TabBarVC
import UIKit
class TabBarVC: UITabBarController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
NavVC
import UIKit
class navVC: UINavigationController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
CheckpointVC.swift
import UIKit
class CheckpointVC: UITableViewController {
//the variable we'll pass the data to from the starting viewcontroller
var data: String = ""
#IBOutlet weak var theHeader: UINavigationItem!
override func viewDidLoad() {
super.viewDidLoad()
theHeader.title = data
}
override func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 0
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return 10
}
}