Unknown class QuoteDetailViewController in Interface Builder file with Xcode 12

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Created Aug ’21

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I saw a lot of posts about this error in Xcode but all of them are quite old. I'm learning how to code in Swift and I'm following the instruction of book.

My Xcode is version 12.5.1. The goal of this app is to display a list of quotes (string) and when I tap on one of them, display a new view that has as a title the quote.

I have a very simple storyboard. There is a TableView with a segue to a View. I created a new Cocoa file for tableview. TableView is working.

I connect the TableView with the View.

I repeated the some process for the View. I added a new Cocoa file called QuoteDetailViewController, click on top of the view and in the Class I selected from the list the file.

When I run the application in the iPhone 11 simulator, the view doesn't have any quote as title. I put a breakpoint in the code connected to the TableView and the app stops there. If I put a breakpoint in the QuoteDetailViewController nothing happens but I see an error in the output

2021-08-11 19:13:17.215204+0100 QuoteApp[80238:4055489] [Storyboard] Unknown class QuoteDetailViewController in Interface Builder file.

The QuoteDetailViewController is very basic.

The QuoteDetailViewController is very basic.

    import UIKit

    class QuoteDetailViewController: UIViewController {

        override func viewDidLoad() {
            super.viewDidLoad()
        }
        
        override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
            if let quoteViewController = segue.destination as? QuoteDetailViewController {
                if let selectedQuote = sender as? String {
                    quoteViewController.title = selectedQuote
                }
            }
        }
    }

I tried to build again and again the app. I tried to Clean Build Folder and build again. I tried to recreate the View and the code. After all of that, nothing changed. The error is still there.

The source code is on GitHub.

Update

If I click on the arrow at the end of Class and just before the dropdown, Xcode opens the file I expect to be opened.

Answered by ForumsContributor in

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Answer 1

Claude31 OP

Aug ’21

Accepted Answer

You put the prepare in the wrong class.

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destination.
        // Pass the selected object to the new view controller.
        if let quoteViewController = segue.destination as? QuoteDetailViewController {
            if let selectedQuote = sender as? String {
                quoteViewController.quote = selectedQuote
            }
        }
    }

It should be in the QuoteTableViewController and not in QuoteDetailViewController.

I changed and now one get the label.

Simulator Screen Shot - iPhone 12 Pro Max - 2021-08-12 at 15.42.16.png

In fact, there is no segue from QuoteDetailViewController.

Note: the code on GitHub is

quoteViewController.quote = selectedQuote

not

quoteViewController.title = selectedQuote

Just change and get :

ScreenShot 2.png

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