SwiftUI - Indexset to index in array

问题

I am using ForEach within a NavigationView and list combined with a function called when the user deletes a row using .onDelete() as per below.

struct PeriodListView: View {
@ObservedObject var theperiodlist = ThePeriodList()
@EnvironmentObject var theprofile: TheProfile

@State private var showingAddPeriod = false

var dateFormatter: DateFormatter {
    let formatter = DateFormatter()
    formatter.dateStyle = .long
    return formatter
}

var body: some View {
    NavigationView {
        List {
            ForEach(theperiodlist.periods) {period in
                PeriodRow(period: period)
            }
            .onDelete(perform: removePeriods)
        }
        .navigationBarTitle("Periods")
            .navigationBarItems(trailing:
                Button(action: {self.showingAddPeriod = true}) {
                    Image(systemName: "plus")
                }
            )
        .sheet(isPresented: $showingAddPeriod) {
            AddPeriod(theperiodlist: self.theperiodlist).environmentObject(self.theprofile)
        }
    }
}
func removePeriods(at offsets: IndexSet) {
    AdjustProfileRemove(period: theperiodlist.periods[XXX])
    theperiodlist.periods.remove(atOffsets: offsets)
}

I have a separate function (AdjustProfileRemove(period)) which I want to call with the removed period as the variable - e.g. I want to find XXX in AdjustProfileRemove(period: theperiodlist.periods[XXX]). Is there a simple way to do this (I am guessing from IndexSet) or am I missing something fundamental?

Thanks.

回答1:

.onDelete is declared as

@inlinable public func onDelete(perform action: ((IndexSet) -> Void)?) -> some DynamicViewContent

IndexSet is simply Set of all indexes of the elements in the array to remove. Let try this example

var arr = ["A", "B", "C", "D", "E"]
let idxs = IndexSet([1, 3])

idxs.forEach { (i) in
    arr.remove(at: i)
}
print(arr)

so the resulting arr is now

["A", "C", "D"]

The reason, why .onDelete use IndexSet is that more than one row in List could be selected for delete operation.

BE CAREFULL! see the resulting array! Actually removing elements one by one needs some logic ...

Let's try

var arr = ["A", "B", "C", "D", "E"]
let idxs = IndexSet([1, 3])

idxs.sorted(by: > ).forEach { (i) in
    arr.remove(at: i)
}
print(arr)

it works now as you expected, is it? the result now is

["A", "C", "E"]

Based on

theperiodlist.periods.remove(atOffsets: offsets)

it seems, that the ThePeriodList already has build-in function with required functionality.

in your case just replace

AdjustProfileRemove(period: theperiodlist.periods[XXX])

with

offsets.sorted(by: > ).forEach { (i) in
    AdjustProfileRemove(period: theperiodlist.periods[i])
}

回答2:

Here is possible approach (taking into account that in general offsets can contain many indexes)

func removePeriods(at offsets: IndexSet) {
    theperiodlist.periods = 
        theperiodlist.periods.enumerated().filter { (i, item) -> Bool in
            let removed = offsets.contains(i)
            if removed {
                AdjustProfileRemove(period: item)
            }
            return !removed
        }.map { $0.1 }
}

来源：https://stackoverflow.com/questions/59868180/swiftui-indexset-to-index-in-array

标签

arrays

swift

swiftui