I am (slowly) progressing on building a cookbook app for my mother’s recipes.
I have built a ContentsViewController, in which I have a UICollectionView that displays a collection of Chapters in the body of the screen. The ChapterCell has a chapterImage and a chapterName.
When a user taps a Chapter, the screen segues to the ChapterViewController. The collection of Chapters then displays in the left-hand column, and a table of recipes will appear in the body of the screen.
My intention is to re-use the ChapterCell in that left-hand column, but when I do, I get the following app crash in AppDelegate
unexpectedly found nil while unwrapping an optional value uicollectionviewcell
I have put a breakpoint in and done various versions of ‘po chapter’ through to ‘po chapterToDisplay!chapterName’ and values are returned.
As a workaround to keep me going, I have created an almost identical ChapterCell and called it ChapChapterCell. BUT this is going to gnaw away at me, and would like to know one way or the other.
Having googled around, I can see stuff about using multiple collection view in a view controller, but nothing much about what I am trying to do.
… So can multiple view controllers use a single uicollectionviewcell?
I know it is possible, as I have looked at a different app I built and it shares a common ‘uitableviewcell’. And in the cookbook app I am building I am getting the same error for the ‘uitableviewcell’ as the ‘uicollectionviewcell’. This is despite following the same code patern from the previous app. Something else is going wrong, as I am able to run the other app in Xcode 11.3 simulator / devices just fine. Just not the new one.
The difference between the two apps, is the original app only has an ‘AppDelegate.swift’ file, whereas the new one has both an ‘AppDelegate.swift’ file, as well as a ‘SceneDelegate.swift’ file. I am deducing that the problem has got to be in there somewhere.
***Assertion failure in -[UITableView _dequeueReusableCellWithIdentifier:forIndexPath:usingPresentationValues:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKitCore_Sim/UIKit-3901.4.2/UITableView.m:8624
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'unable to dequeue a cell with identifier TableOfRecipesCell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard'
The app works on the first View Controller, but when I tap a row in the second View Controller it crashes the app.
As mentioned, I have double- through quintuple-checked that the second VC and Cell have the cell identifier is correctly set up. It is the same problem for both the Collection and Table views.
I have also tried copying over the ‘AppDelegate’ file from the original app to the new app, but this does not fix it.
My conclusion is that a different code pattern is needed to handle reusing Cell views across View Controllers when both an ‘AppDelegate.swift’ file, as well as a ‘SceneDelegate.swift’ file is automatically included in a new app. OR it is no longer possible to reuse Cell views across View Controllers - but that would be daft!!
Hey @lachlan. Feel free to zip up your project, and send it over to me, and I will take a look. You can send me the version without the workaround, and I will do my best to debug.
Please upload the file to a file sharing service like Box, and paste the link in here. Also, make sure to zip up the entire project folder, not just the Xcode file.
Hi David, thanks for replying and offering to help. I have the app up in GitHub. I can add you as a collaborator (assuming you have an account name you could send me)
Oh, you will see another collaborator there too, who is an iOS developer my employer uses as a contractor, but I normally prefer not to bother her (she is also on holidays at the moment) … but I was at my wits-end!
Also, I have left the CollectionView workaround in there ‘ChapChapterCell’ as a duplicate of ‘ChapterCell’. But the TableOfRecipeCell problem is still there. And I am assuming if a solution is found for TableView, then it would likely be the same for Collection View
Okay, I started looking at your code. It seems like the array that you are getting back from cookbook.chapters[selectedChapterIndex].recipes in cookbookRetrieved is empty, causing your recipes array to be empty. Is this what you intended?
No it is not intended. The same code paternities was used in ChapterViewController, and it works there. But it is empty in RecipeVC it should be populated.
As mentioned above, I have put a breakpoint in at that point and done various versions of ‘po chapter’ through to ‘po chapterToDisplay!chapterName’ and values are returned.
The crash happens after that point in AppDelegate
I have just fixed that as I was referencing selectedChapterIndex. I will push another build of the app, as the same problem is still happening. Putting a breakpoint there now has po recipes returning
it should be populated.