Question 371379 in IOS Swift Question posted in
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Ios swift – Deleting item of sorted data in a ForEach

I have a ForEach that I use to display some info, sorted on it’s date attribute:

My view looks like:

ForEach(records.sorted(by: < ), id: .self) { record in
                Text("(record.date")
            }
            .onDelete(perform: deleteRecord)

Record.swift

class Record : Comparable {
    
    var value: Float
    var date: Date
    
    
    init(value: Float = 0.0, date: Date = Date.now) {
        self.value = value
        self.date = date
    }
    
    static func < (lhs: Record, rhs: Record) -> Bool {
        return lhs.date < rhs.date
    }
    
}

My problem is that whenever I delete an item, the wrong one is actually removed.

deleteRecord()

func deleteRecord(_ indexSet: IndexSet) {
        for index in indexSet {
            movement.records.remove(at: index)
        }
    }

I’v tried changing the deleteRecord() method to something like:

func deleteRecord(at offsets: IndexSet) {
        movement.records.remove(atOffsets: offsets)
    }

but this did not solved my issue.

Tags:

3

Answers


  1. Chosen as BEST ANSWER
    0

    I managed to make a simple solution:

    First I sorted the ForEach like this:

        ForEach(records.sorted(by: {$0.date < $1.date}), id:  .self) { record in
            Text("(record.date)")      
        }
        .onDelete(perform: deleteRecord)

    After that, in deleteRecord():

            func deleteRecord(_ indexSet: IndexSet) {
        
        // Sorting the data before it's in the view
        var tmpSortedData = records.sorted(by: {$0.date < $1.date})
         
        // Removing the item
         for index in indexSet {
             tmpSortedData.remove(at: index)
         }
         
        // Updating data model
        records = tmpSortedData
    
    }

  2. 0

    You can sort the record array not on the ForEach but after you add the records.

    Remove the .sorted(by: < ) from the ForEach and add it to the end of the data fetching. And it should work like a charm.

    Warning: You should create a temporary array, sort the temporary array and then save it to records so it doesn’t do some weird moving animations.

    Tip: You should use structs instead of classes. Because classes are reference type and structs are value type.
    More info about it here: Value And Reference Types In Swift

    Login or Signup to reply.
  3. 0

    Problem

    The index of your sorted array and the original index of the records data are different. That’s why you are removing wrong item.

    Solution

    You can make a conversion of your sorted item index to the original index in your delete function. I’m sharing the demo code:

    class Record: Equatable {
    var value: Float
    var date: Date
    
    
    init(value: Float = 0.0, date: Date = Date.now) {
        self.value = value
        self.date = date
    }
    
    static func == (lhs: Record, rhs: Record) -> Bool {
        return lhs.value == rhs.value
    }
    
    static func < (lhs: Record, rhs: Record) -> Bool {
        return lhs.value < rhs.value
    }
}

struct ContentView: View {
    @State private var records: [Record] = [.init(value: 4, date: .now), .init(value: 2, date: .now), .init(value: 3, date: .now)]
    
    private var sortedRecords: [Record] {
        records.sorted(by: <)
    }
    
    var body: some View {
        List {
            ForEach(sortedRecords, id: .value) { record in
                Text("Value: (record.value)")
            }
            .onDelete(perform: deleteRecord)
        }
    }
    
    func deleteRecord(_ indexSet: IndexSet) {
        for index in indexSet {
            let recordToRemove = sortedRecords[index]
            guard let indexToDelete = records.firstIndex(of: recordToRemove) else { return } // --> Here it is
            records.remove(at: indexToDelete)
        }
    }
}

    Note this is a demo code, because I don’t know what’s your movement property is doing, or any other details which you haven’t shared. I guess you can update your code according to this demo.

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