Checklists v5.0 Optional error on configureCheckmark method

📚 Official Books iOS Apprentice
1

Am on page 112 of the PDF version with the configureCheckmark method, and for the line which starts “let label =”, the debugger reads: “fatal error: unexpectedly found nil while unwrapping an Optional value” I have configured the new label with checkmark in the storyboard, and have set its tag attribute to 1001.

import UIKit

class ChecklistViewController: UITableViewController, AddItemViewControllerDelegate {
    
    var items: [ChecklistItem]
    
    required init?(coder aDecoder: NSCoder) {
        items = [ChecklistItem]()
        
        let row0item = ChecklistItem()
        row0item.text = "Walk the dog"
        row0item.checked = false
        items.append(row0item)
        
        let row1item = ChecklistItem()
        row1item.text = "Brush my teeth"
        row1item.checked = true
        items.append(row1item)
        
        let row2item = ChecklistItem()
        row2item.text = "Learn iOS development"
        row2item.checked = true
        items.append(row2item)
        
        let row3item = ChecklistItem()
        row3item.text = "Soccer practice"
        row3item.checked = false
        items.append(row3item)
        
        let row4item = ChecklistItem()
        row4item.text = "Eat ice cream"
        row4item.checked = true
        items.append(row4item)
        
        super.init(coder: aDecoder)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "ChecklistItem", for: indexPath)
        
        let item = items[indexPath.row]
        
        configureText(for: cell, with: item)
        configureCheckmark(for: cell, with: item)
        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath:IndexPath) {
        
        if let cell = tableView.cellForRow(at: indexPath) {
            let item = items[indexPath.row]
            item.toggleChecked()
            
            configureCheckmark(for: cell, with: item)
        }
        tableView.deselectRow(at: indexPath, animated: true)
    }
    
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath:IndexPath) {
        
        items.remove(at: indexPath.row)
        
        let indexPaths = [indexPath]
        tableView.deleteRows(at: indexPaths, with: .automatic)
    }
    
    func configureCheckmark(for cell: UITableViewCell, with item: ChecklistItem) {
        
        let label = cell.viewWithTag(1001) as! UILabel
        
        if item.checked {
            label.text = "√"
        } else {
            label.text = ""
        }
    }
    
    func configureText(for cell: UITableViewCell, with item:ChecklistItem) {
        let label = cell.viewWithTag(1000) as! UILabel
        label.text = item.text
    }
    
    
    func addItemViewControllerDidCancel(_ controller: AddItemViewController) {
        dismiss(animated: true, completion: nil)
    }
    
    func addItemViewController(_ controller: AddItemViewController, didFinishAdding item: ChecklistItem) {
        let newRowIndex = items.count
        items.append(item)
        
        let indexPath = IndexPath(row: newRowIndex, section: 0)
        let indexPaths = [indexPath]
        tableView.insertRows(at: indexPaths, with: .automatic)
        
        dismiss(animated: true, completion: nil)
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        
        if segue.identifier == "AddItem" {
            let navigationController = segue.destination as! UINavigationController
            let controller = navigationController.topViewController as! AddItemViewController
            controller.delegate = self
        }
    }

}
2

A few possibilities:

  • there is another view with tag 1001 (although then the error message would be different, so it’s probably not this)
  • you did not put the label inside the cell’s Content View but possibly elsewhere
3

Hi,

Is there a solution to this? I get the exact same error…can’t figure out why this is happening.

Thanks,
D.

4

Here’s my code:

import UIKit

class ChecklistViewController: UITableViewController, AddItemViewControllerDelegate {

var items: [ChecklistItem]

required init?(coder aDecoder: NSCoder) {
    items = [ChecklistItem]()
    
    let row0item = ChecklistItem()
    row0item.text = "Walk the dog"
    row0item.checked = false
    items.append(row0item)
    
    let row1item = ChecklistItem()
    row1item.text = "Brush my teeth"
    row1item.checked = true
    items.append(row1item)
    
    let row2item = ChecklistItem()
    row2item.text = "Learn iOS Development"
    row2item.checked = true
    items.append(row2item)
    
    let row3item = ChecklistItem()
    row3item.text = "Soccer practice"
    row3item.checked = false
    items.append(row3item)
    
    let row4item = ChecklistItem()
    row4item.text = "Eat ice cream"
    row4item.checked = true
    items.append(row4item)
    
    super.init(coder: aDecoder)
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

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

override func tableView(_ tableView: UITableView,
                        cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(
        withIdentifier: "ChecklistItem", for: indexPath)
    
    let item = items[indexPath.row]
    
    configureText(for: cell, with: item)
    configureCheckmark(for: cell, with: item)
    return cell
}

override func tableView(_ tableView: UITableView,
                        didSelectRowAt indexPath: IndexPath) {
    
    if let cell = tableView.cellForRow(at: indexPath) {
    let item = items[indexPath.row]
        item.toggleChecked()
        configureCheckmark(for: cell, with: item)
    }
    
    tableView.deselectRow(at: indexPath, animated: true)
}

override func tableView(_ tableView: UITableView,
                        commit editingStyle: UITableViewCellEditingStyle,
                        forRowAt indexPath: IndexPath) {
    // 1 - removes items from data model
    items.remove(at: indexPath.row)
    
    // 2 - delete corresponding row from table
    let indexPaths = [indexPath]
    tableView.deleteRows(at: indexPaths, with: .automatic)
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    // 1
    if segue.identifier == "AddItem" {
        // 2
        let navigationController = segue.destination as! UINavigationController
        // 3
        let controller = navigationController.topViewController as! AddItemViewController
        // 4
        controller.delegate = self
    }
}

func configureCheckmark(for cell: UITableViewCell, with item: ChecklistItem) {
    let label = cell.viewWithTag(1001) as! UILabel
    
    if item.checked {
        label.text = "√"
    } else {
        label.text = ""
    }
}

func configureText(for cell: UITableViewCell, with item: ChecklistItem) {
    let label = cell.viewWithTag(1000) as! UILabel
    label.text = item.text
}

func addItemViewControllerDidCancel(_ controller: AddItemViewController) {
    dismiss(animated: true, completion: nil)
}

func addItemViewController(_ controller: AddItemViewController, didFinishAdding item: ChecklistItem) {
    let newRowIndex = items.count
    items.append(item)
    
    let indexPath = IndexPath(row: newRowIndex, section: 0)
    let indexPaths = [indexPath]
    tableView.insertRows(at: indexPaths, with: .automatic)
    
    dismiss(animated: true, completion: nil)
}

}
5

If you zip up your project folder and upload it somewhere, I can take a look.

6

Hi Hollance,

Wow. thanks for the super quick reply. I’ve just been playing around with the code and I seem to have got it working? Not sure how but hey…it’s working. Thanks for your help :slight_smile:

7

Hey buddy,

Okay. So I wasn’t convinced when I (somehow) managed to fix the error, so I deleted my files and started the exercise again (as I want to know how it works rather than just accepting it does)…anyway, I deleted my files and restarted the exercise, and when I get to the same point on pg 112 I get the exact same error…but this time I really have no idea what I did to fix it, or even how to fix it. Also, for (whatever reason) I can’t upload a file to this message (I get a message saying new users can’t)…anyway, below is a link to download my project…if you could have a quick look at it, it would be hugely appreciated.

https://wetransfer.com/downloads/755e3f2becb43dea81440d9f93a5f48c20170519133357/c57ae43ff8fcbffed725ee4d073a0d0520170519133357/215d1a

Thanks in advance.

Best,
D.

8

So I’ve deleted the last bit of code on page 112 (change “configureCheckmark(for:with)” to go back one step and the app runs fine at that point. As soon as I add in the new code I get the error. Not sure if I’m missing a step. Do I need to link the “√” label to somewhere?

Thanks,
D.

EDIT: So I figured it out. I was being a dumbass. I put the label on the wrong view controller. The code works brilliantly. Thanks for your help :grinning:

9

Ah good. I didn’t have time earlier to look so I’m glad you managed to figure it out. :smile:

10

Sorry to revive this old topic, but I am having the same old problem in V6. The program crashes when I try to get it to run, and I get the message “Fatal error: Unexpectedly found nil while wrapping an Optional”. Following is my code for the ChecklistViewController:

import UIKit

class ChecklistViewController: UITableViewController, AddItemViewControllerDelegate {
    
    
    
    var items: [ChecklistItem]
    
    required init?(coder aDecoder: NSCoder) {
        items = [ChecklistItem]()
        
        let row0item  = ChecklistItem()
        row0item.text = "Walk the dog"
        row0item.checked = false
        items.append(row0item)
        
        let row1item = ChecklistItem()
        row1item.text = "Brush my teeth"
        row1item.checked = true
        items.append(row1item)
        
        let row2item = ChecklistItem()
        row2item.text = "Learn iOS development"
        row2item.checked = true
        items.append(row2item)
        
        let row3item = ChecklistItem()
        row3item.text = "Soccer practice"
        row3item.checked = false
        items.append(row3item)
        
        let row4item = ChecklistItem()
        row4item.text = "Eat ice cream"
        row4item.checked = true
        items.append(row4item)
        
        super.init(coder: aDecoder)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        navigationController?.navigationBar.prefersLargeTitles = true
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "ChecklistItem", for: indexPath)
        let item = items[indexPath.row]
        let label = cell.viewWithTag(1000) as! UILabel

        label.text = item.text
        
        configureText(for: cell, with: item)
        configureCheckmark(for: cell, with: item)
        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        
        if let cell = tableView.cellForRow(at: indexPath) {
            
            let item = items[indexPath.row]
            item.toggleChecked()
            configureCheckmark(for: cell, with: item)
        }
        tableView.deselectRow(at: indexPath, animated: true)
    }
    
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        items.remove(at: indexPath.row)
        
        let indexPaths = [indexPath]
        tableView.deleteRows(at: indexPaths, with: .automatic)
    }
    
    func configureText(for cell: UITableViewCell, with item: ChecklistItem) {
        
        
        let label = cell.viewWithTag(1000) as! UILabel
        label.text = item.text
    }

    
    func configureCheckmark(for cell: UITableViewCell, with item: ChecklistItem) {
        
        let label = cell.viewWithTag(1001) as! UILabel
        
        
        if item.checked {
            label.text = "√"
        } else {
            label.text = ""
        }
    }
    
    func addItemViewControllerDidCancel(_ controller: AddItemViewController) {
        navigationController?.popViewController(animated: true)
    }
    
    func addItemViewController(_ controller: AddItemViewController, didFinishAdding item: ChecklistItem) {
        
        let newRowIndex = items.count
        items.append(item)
        
        let indexPath =  IndexPath(row: newRowIndex, section: 0)
        let indexPaths = [indexPath]
        tableView.insertRows(at: indexPaths, with: .automatic)
        
        navigationController?.popViewController(animated: true)
    }
    
//    @IBAction func addItem() {
//        let newRowIndex = items.count
//
//        let item = ChecklistItem()
//        item.text = "I am a new row"
//        item.checked = false
//        items.append(item)
//
//        let indexPath = IndexPath(row: newRowIndex, section: 0)
//        let indexPaths = [indexPath]
//        tableView.insertRows(at: indexPaths, with: .automatic)
//    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "AddItem" {
            
            let controller = segue.destination as! AddItemViewController
            controller.delegate = self
        }
    }

}
11

Sorry to hear that you’re still having trouble. Could you either provide the full text of the error message from the Xcode console, or better yet, provide a copy of your project so that I can test it out at my end to see what is going? That way, I can see what is going on without having to guess at whether perhaps an outlet is not connected or a few other issues that I can’t see just by looking at the provided code :slight_smile: