SwiftUI TabView gives an error message during add/delete the element of CoreData

Question

I am currently trying to use TabView for carousel view(PageTabViewStyle) with CoreData.

The error doesn't occur, when I add a new page in order like this age.name: 3, page.name: 4, page.name: 5

But the error occurs, if I put a number in the first/middle order like page.name: 2

If I put page.name: 6, then no error and it's also same with Alphabet. b c d e -> put "f", no problem, but put "a" error.

After turn off the app and open the app, then I see the updated(Page added/Page deleted) ContentView anyway.

I guess, TabView has a sorting problem, so I tried to sort the list of CoreData, change LifeCycle to SwiftUI, but the error occurs again and again. I've also tried with Firebase, but the same problem.

Error Message:

"libc++abi: terminating with uncaught exception of type NSException
    *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to delete item 1 from section 0 which only contains 1 items before the update'
    terminating with uncaught exception of type NSException"

ContentVIew

TabView() {
    ForEach(pages, id: \.self) { page in
        SubPage(whichPage: page)
    }
}
.tabViewStyle(PageTabViewStyle())
.indexViewStyle(PageIndexViewStyle(backgroundDisplayMode: .always))

AddPage

let page = Page(context: self.moc)
        page.name = pageName

        do {
            print("page.name: \(page.name ?? "Unknown")")
            try self.moc.save()
            
        } catch {
            print(error)
        }

SubPage

@FetchRequest(entity: Page.entity(),
              sortDescriptors: [NSSortDescriptor(keyPath: \Page.name, ascending: true)]
) var pages: FetchedResults<Page>

var whichPage: FetchedResults<Page>.Element

Using VStack or HStack or List instead of TabView works fine without any problem.

`TabView` is not really flexible you would have to create your own `View` to mimic it. — lorem ipsum, May 10 '21 at 13:19
I've run into the same problem. Hoping someone here can offer a solution that allows us to continue to use TabView. — tkhelm, May 25 '21 at 22:37
@tkhelm I've checked just now that this problem is solved in Xcode 13 Beta & iOS15! — Taeeun Kim, Jun 08 '21 at 15:43
I'd like to point our this questions and accepted answer for a very simple iOS 14 workaround: https://stackoverflow.com/a/68423533/12764795 — Marco Boerner, Jul 18 '21 at 23:15

Taeeun Kim · Accepted Answer · 2021-06-08T15:56:57.300

0

Finally, this problem is solved in Xcode 13 & iOS 15 based!

Full Code

TabView {
    ForEach(pages) { page in
        SubPage(whichPage: page)
    }
}
.tabViewStyle(PageTabViewStyle())

or

TabView {
    ForEach(pages) { page in
        SubPage(whichPage: page)
    }
}
.tabViewStyle(.page)

edited Jun 08 '21 at 15:56

answered Jun 08 '21 at 15:33

Taeeun Kim

964
1
8
20

SwiftUI TabView gives an error message during add/delete the element of CoreData

1 Answers1

Linked