Passing data through a UINavigationController to a UIViewController - uinavigationcontroller

Question

When an item is selected by the user, I'm trying to pass the selected item's index along with a reference to the records controller to a UINavigationController. The problem I'm having is that I'm not sure how to pass those variables properly. I was trying to avoid passing them 'the wrong way'. [EDIT: The application works perfectly if I save the items in static variables within AppDelegate]
Below I show the code that runs when the user selects an item, the code that runs in the navigation controller (which uses an incorrect way to pass the variables), and finally the code that runs on the view controller that indicates the variables are not being passed.
Here's the code for when the user selects an item:
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let storyboard = storyboard, let controller = storyboard.instantiateViewController(withIdentifier: "DetailNavigationController") as? DetailNavigationController else {
print("ERROR: didn't get the view controller we expected")
return
}
print("initializing the newly created page view controller with index \(indexPath.row)")
controller.bIndexPath = indexPath
controller.bController = bController
present(controller, animated: true, completion: nil)
}
.
That causes the `DetailNavigationController.viewDidLoad()` to run:
override func viewDidLoad() {
super.viewDidLoad()
print("DetailNavigationController vdl and index \(bIndexPath.row)")
guard let storyboard = storyboard, let controller = storyboard.instantiateViewController(withIdentifier: "ManagePageViewController") as? ManagePageViewController else {
print("ERROR: didn't get the view controller we expected")
return
}
controller.bIndexPath = bIndexPath
controller.bController = bController
}
.
The output from that proves that the data is being passed this far:
DetailNavigationController vdl and index 4
But in ManagePageViewController we apparently don't get the same instance, because the variables are not set. I "knew this wouldn't work", but didn't know what else to try.
So below we see the ManagePageViewController.viewDidLoad():
override func viewDidLoad() {
super.viewDidLoad()
print("viewDidLoad ManagePageViewController \(bIndexPath)")
if let viewController = viewPhotoCommentController(currentIndex ?? 0) {
if let bController = bController {
viewController.bController = bController
} else {
print("ManagePageViewController viewDidLoad bController.performFetch")
let bSortedByName = SaucerItem.order(Column("name").asc, Column("name"))
bController = try! FetchedRecordsController(dbQueue, request: bSortedByName)
try! bController.performFetch()
vController.brewController = bController
}
let viewControllers = [viewController]
print("setting a view controller instance with currentIndex \(currentIndex ?? 0)" )
setViewControllers(viewControllers, direction: .forward, animated: false, completion: nil)
}
dataSource = self
}
.
And the output that shows going down the path of making new `bController`:
viewDidLoad ManagePageViewController nil
ManagePageViewController initializing the newly created page view controller with index 0
ManagePageViewController viewDidLoad bController.performFetch
setting a view controller instance with currentIndex 0
.
So that indicates the variables set earlier must have been on some other instance, so that's the wrong approach.
I thought I could make the settings in AppDelegate, but that just seemed wrong to me. There must be a way to pass the data cleanly. Some other things I tried included using the facilities contained within the UINavigationController to figure out what it was going to run, and set the variables on that instance, but I wasn't able to discover the instance that the controller was going to run.
Additional Information:
In order to answer a question about why it seems like I'm going from "A" to "C" through "B", I'll place a diagram here and try to explain why. The bottom line is that it must be configured this way to enable the paging on the detail screen.
Printing controller from DetailNavigationController.viewDidLoad() said ManagePageViewController, and printing viewController from ManagePageViewController.viewDidLoad() said PageViewController.
So what's the right way to pass this information to the next view controller?