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SOLVED: Day 58 CoreData One to many relationship Country to Candy - What is the best way to delete a candy object in the list

Forums > 100 Days of SwiftUI
@mradTime  HWS+

struct OneToManyCandyView: View { @Environment(.managedObjectContext) var moc @FetchRequest(sortDescriptors: []) var countries: FetchedResults<Country>

var body: some View {
    VStack {
        List {
            ForEach(countries, id: \.self) { country in
                Section(country.wrappedFullName) {
                    ForEach(country.candyArray, id: \.self) { candy in
                        Text(candy.wrappedName)
                    }
                }
            }
        }

        Button("Add") {
            let candy1 = Candy(context: moc)
            candy1.name = "Mars"
            candy1.origin = Country(context: moc)
            candy1.origin?.shortName = "UK"
            candy1.origin?.fullName = "United Kingdom"

            let candy2 = Candy(context: moc)
            candy2.name = "KitKat"
            candy2.origin = Country(context: moc)
            candy2.origin?.shortName = "UK"
            candy2.origin?.fullName = "United Kingdom"

            let candy3 = Candy(context: moc)
            candy3.name = "Twix"
            candy3.origin = Country(context: moc)
            candy3.origin?.shortName = "UK"
            candy3.origin?.fullName = "United Kingdom"

            let candy4 = Candy(context: moc)
            candy4.name = "Toblerone"
            candy4.origin = Country(context: moc)
            candy4.origin?.shortName = "CH"
            candy4.origin?.fullName = "Switzerland"

            if moc.hasChanges {
                try? moc.save()
            }
        }
    }
}

}

2      

@delawaremathguy  HWS+

hi mrad,

to delete from the sectioned list by swiping, attach this .onDelete modifier to the inner loop:

ForEach(country.candyArray, id: \.self) { candy in
  Text(candy.wrappedName)
}
.onDelete { offsets in deleteCandies(at: offsets, country: country) }

and then add the function deleteCandies to your View:

func deleteCandies(at offsets: IndexSet, country: Country) {

  // (1) identify candies to delete in the country's candyArray
  var candiesToDelete = [Candy]()
  for offset in offsets {
    candiesToDelete.append(country.candyArray[offset])
  }

  // (2) ask the managed object context to delete each of these
  for candy in candiesToDelete {
    moc.delete(candy)
  }

  // (3) save to disk
  try? moc.save()
}

hope that helps,

DMG

3      

@mradTime  HWS+

Thank you DMG.

2      

@TuTees  

Hi @delawaremathguy,

I know this is many months later but I am asking in hopes that you might see this and help me. I've been trying to take your solution above and adapt it to work with a .onTapGesture modifier instead of the .onDelete modifer like so:

List {
    ForEach(countries, id: \.self) { country in
        Section(country.wrappedFullName) {
            ForEach(country.candyArray, id: \.self) { candy in
                Text(candy.wrappedName)
                    .onTapGesture {
                        offsets in deleteCandies(at: offsets, country: country)
                    }
            }
        }
    }
}

The problem I have been running into is trying to figure out how to get the IndexSet which your function requires.

So how could I find the IndexSet and make all this work with the .onTapGesutre modifer as shown above.

Thanks

2      

@haeffb  HWS+

The .onTapGesture should provide the candy entity for the row tapped.

Offsets are provided by the .onDelete modifier and aren't available/provided by .onTapGesture.

I think - but haven't verfied - adding this to the .onTapGesture should do the trick...

moc.delete(candy)

try? moc.save()

2      

@TuTees  

Sadly this won't work, and its because the data of the ForEach loop is coming from country.candyArray which looks like this:

public var candyArray: [Candy] {
        let set = candy as? Set<Candy> ?? []

        return set.sorted {
            $0.wrappedName < $1.unwrappedName
        }
    }

2      

@TuTees  

So I have created a janky modified func from Chat-GPT which creates an somewhat solution and I am not entirely confident its actually deleteing anything.

@State private var indexSet = IndexSet()

func indexSet(for candy: Candy, at country: Country) -> IndexSet {
    var indexSet = IndexSet()
        for (index, arrayItem) in country.candyArray.enumerated() {
            if arrayItem == candy {
                indexSet.insert(index)
            }
        }
        return indexSet
    }
}
ForEach(countries, id: \.self) { country in
    Section(country.wrappedFullName) {
         ForEach(country.candyArray, id: \.self) { candy in
             Text(candy.wrappedName)
                 .onTapGesture {
                     indexSet = self.indexSet(for: candy, at: country)
                         deleteTask(at: indexSet, country: country)

                         print(group.taskArray.count)
                  }
             }
       }
 }

It will "delete" and save but there is no animation and I honestly believe there has to be a more elegant way that will make swiftui more happy

Edit: I have got the animation to work and that is by using withAnimation in the deleteCandies function

2      

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