TableView seguing and cause unexpectedly nil returned - ios

Question

Here is my current setup:
MainMenuViewController -> SubMenuViewController -> UserInputViewController -> ResultViewController
All of my view controllers contains a tableView.
When a user taps on a cell in MainMenuViewControlle, it will segue to SubMenuViewController. All fine and dandy.
Here is where it gets tricky, in SubMenuViewController, there are cells that needs to instantiate another SubMenuViewController because the sub menu options can be several levels deep.
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let selectedNode = node?.childenNode[indexPath.row] else {
return
}
if selectedNode.isLeaveNode() {
performSegue(withIdentifier: "userInput", sender: self)
} else {
let subMenuViewController = SubMenuViewController(node: selectedNode)
self.navigationController?.pushViewController(subMenuViewController, animated: true)
}
When there are no child nodes, then it will segue to UserInputViewController, but when there are more options, it needs to instantiate another SubMenuViewController and the tableView will populate itself based on cell the user had tapped previously until selectedNode.isLeaveNode() is true (which means there won't be any child nodes).
This problem is when this code runs :
let subMenuViewController = SubMenuViewController(node: selectedNode)
self.navigationController?.pushViewController(subMenuViewController, animated: true)
it give me the following error:
fatal error: unexpectedly found nil while unwrapping an Optional value
From where I registered my cells which is here:
let bundle = Bundle(for: type(of: self))
let nib = UINib(nibName: "SubMenuTableViewCell", bundle: bundle)
tableView.register(nib, forCellReuseIdentifier: "SubMenuCell")
All my tableView cells are instantiated using a xib file, and I have registered my cells in viewDidLoad()
Can anybody see the problem?
UPDATE
Here is the rest of my code:
UIViewController
class SubMenuViewController: UIViewController {
var node: Node?
init(node: Node) {
self.node = node
super.init(nibName: nil, bundle: nil)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
#IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.isNavigationBarHidden = false
self.navigationItem.title = node?.value.rawValue
let bundle = Bundle(for: type(of: self))
let nib = UINib(nibName: "SubMenuTableViewCell", bundle: bundle)
tableView.register(nib, forCellReuseIdentifier: "SubMenuCell")
}
}
UITableViewDataSource
extension SubMenuViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return node!.childCount
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
print("called")
let cell = tableView.dequeueReusableCell(withIdentifier: "SubMenuCell", for: indexPath) as! SubMenuTableViewCell
let desciptionModule = node?.childenNode[indexPath.row].value
let description = Modules.description(module: desciptionModule!)
cell.title.text = description.main
cell.subtitle.text = description.sub
return cell
}
}
UITableViewDelegate
extension SubMenuViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 68
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let selectedNode = node?.childenNode[indexPath.row] else {
return
}
if selectedNode.isLeaveNode() {
performSegue(withIdentifier: "userInput", sender: self)
} else {
let subMenuViewController = SubMenuViewController(node: selectedNode)
self.navigationController?.pushViewController(subMenuViewController, animated: true)
}
}
}

Answer 1

In your viewDidLoad() method, make sure to do the following:
Based on the code you've posted, you might be having issues with this line:
let bundle = Bundle(for: type(of: self))
I would recommend replacing it with the following line:
let bundle = Bundle(forClass: self)
or
let bundle = Bundle.main
If you're still having trouble with this, then try modifying the following lines of code:
let nib = UINib(nibName: "SubMenuTableViewCell", bundle: bundle)
to
let nib = UINib(nibName: "SubMenuTableViewCell", bundle: nil)
In your tableView:cellForRowAtIndexPath UITableViewControllerDelegate method, include the following lines:
var cell = tableView.dequeueReusableCellWithIdentifier("SubMenuCell") as? UITableViewCell
if cell == nil {
tableView.registerNib(UINib(nibName: "SubMenuTableViewCell", bundle: nil), forCellReuseIdentifier: "SubMenuCell")
cell = tableView.dequeueReusableCellWithIdentifier("SubMenuCell") as SubMenuTableViewCell!
}
cell.configure(data: data[indexPath.row])
tableView.reloadData()
return cell
Note
Make sure that the UITableViewCell's reuseIdentifier is "SubMenuCell"
Make sure that the SubMenuTableViewCell.xib file's owner is SubMenuTableViewCell
Make sure the Module does not say "None" (i.e. the Module should be the name of your Project's Target).
Make sure to call tableView.reloadData() in your viewDidLoad() function.

Answer 2

Problem solved
The problem lies in the fact that I instantiated my view controller wrong. The line:
let subMenuViewController = SubMenuViewController(node: selectedNode)
only return a raw object with no outlets, that is why I was getting the optional nil error because there weren't a tableView to start with.
The correct approach would be to instantiate it using your storyboard. Each view controller has a storyboard property as an optional, since my view controller exists in a storyboard, that property will not be nil.
Instead of doing this:
let subMenuViewController = SubMenuViewController(node: selectedNode)
self.navigationController?.pushViewController(subMenuViewController, animated: true)
I actually needed to do this:
let subMenuViewController = storyboard!.instantiateViewController("SubMenuViewController")
That way I know for sure that my subMenuViewController will contain my tableView property which is an IBOutlet from storyboard.