Hi, I am new to developpement in xcode and am trying to build my first app in SwiftUI.
I am struggling with multi selection in a list of CoreData Items.
I build an application comparing the functionality when using an Array versus when using CoreData
The Array tab is working as I expect but the Core data tab is not.
Am I doing something wrong or is it a bug?
You can see further details/comments in the code.
Thanks,
import SwiftUI
// ########################################################################################
// XCode
// Version 11.4.1 (11E503a)
// Simulator
// Version 11.4.1 (921.9)
// SimulatorKit 581.9.1
// CoreSimulator 704.12.1
// Device
// iPhone SE (2nd generation)
// ########################################################################################
// ########################################################################################
// the CoreData entity is named MyNumber
// I don't think extending it as Identifiable has any effect but it shouldn't hurt to add it
// ########################################################################################
extension MyNumber: Identifiable {
// ########################################################################################
// the entity has these two fields
// @NSManaged public var id: UUID?
// @NSManaged public var stringValue: String?
// ########################################################################################
}
struct ContentView: View {
// Tab variables
@State private var tabSelection = 0
// Array variables
@State var arrayNumbers = ["One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten"]
@State var arrayEditMode = EditMode.inactive
@State var arraySelection = Set<String>()
// Core Data variables
@State var cdEditMode = EditMode.inactive
// ########################################################################################
// Am I using the correct type ? Set<MyNumber>() : I also tried Set<UUID>() without success
// ########################################################################################
// # Using Set<MyNumber>()
@State var cdSelection = Set<MyNumber>()
// ######## OR ############
// # Using Set<UUID>()
// @State var cdSelection = Set<UUID>()
// #####################################################################
@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: MyNumber.entity(), sortDescriptors:[]) var cdNumbers: FetchedResults<MyNumber>
var body: some View {
TabView(selection: $tabSelection){
// Array Tab
VStack{
Text("Array").font(.largeTitle)
NavigationView {
List(selection: $arraySelection) {
ForEach(arrayNumbers, id: \.self) { number in
Text(number)
}
.onDelete(perform: arrayOnSwipeDelete)
}
.navigationBarTitle("Selected count \(arraySelection.count)")
.navigationBarItems(leading: arrayDeleteButton, trailing: EditButton())
.environment(\.editMode, self.$arrayEditMode)
}
}
.tabItem {
VStack {
Image(systemName: "checkmark")
Text("Array")
}
}
.tag(0)
// Core Data Tab
VStack{
VStack{
Text("Core Data").font(.largeTitle)
Button("Add coredata numbers") {
for number in self.arrayNumbers {
let cdNumber = MyNumber(context: self.moc)
cdNumber.id = UUID()
cdNumber.stringValue = "\(number)"
}
try? self.moc.save()
}.disabled(cdEditMode.isEditing)
}
NavigationView {
List(selection: $cdSelection) {
ForEach(cdNumbers, id: \.id) { number in
Text(number.stringValue ?? "NULL")
}
// #####################################################################
// Problem #1
// Without the onDelete, the left selection column does not appear at all
// To reproduce this
// 1 - click "Add coredata records"
// 2 - Click "Edit"
// #####################################################################
// Problem #2
// With the onDelete, rows can be selected but $cdSelection stays empty
// To reproduce this
// 1 - click "Add coredata records"
// 2 - Click "Edit"
// 3 - Select records (notice the selection count is not updated)
// 4 - Even with some selected records, the trashcan stays disabled because of the disabled event
// 5 - Commenting out the disabled event and clicking on the trashcan should delete records but it does nothing
// #####################################################################
.onDelete(perform: cdOnSwipeDelete)
}
.navigationBarTitle("Selected count \(cdSelection.count)")
.navigationBarItems(leading: cdDeleteButton, trailing: EditButton())
.environment(\.editMode, self.$cdEditMode)
}}
.tabItem {
VStack {
Image(systemName: "xmark")
Text("CoreData")
}
}
.tag(1)
}
}
init() {
// Global Navigation bar customizations
UINavigationBar.appearance().largeTitleTextAttributes = [
.font : UIFont.systemFont(ofSize: 18, weight: UIFont.Weight.bold)]
}
// array functions
private var arrayDeleteButton: some View {
return Button(action: arrayDeleteNumbers) {
if arrayEditMode == .active {
Image(systemName: "trash")
}
}.disabled(arraySelection.count <= 0)
}
private func arrayDeleteNumbers() {
for id in arraySelection {
if let index = arrayNumbers.lastIndex(where: { $0 == id }) {
arrayNumbers.remove(at: index)
}
}
arraySelection = Set<String>()
}
// #####################################################################
// Array selecction is not affected by the presence of the arrayOnSwipeDelete function
// #####################################################################
private func arrayOnSwipeDelete(with indexSet: IndexSet) {
indexSet.forEach { index in
arrayNumbers.remove(at: index)
}
}
// Core Data Functions
private var cdDeleteButton: some View {
return Button(action: cdDeleteNumbers) {
if cdEditMode == .active {
Image(systemName: "trash")
}
// #####################################################################
// Even with a commented .disable rule, the trash can deletes nothing
// #####################################################################
}.disabled(cdSelection.count <= 0)
}
private func cdDeleteNumbers() {
for selectedItem in self.cdSelection{
// #####################################################################
// # Using Set<MyNumber>()
self.moc.delete(selectedItem)
// ######## OR ############
// # Using Set<UUID>()
// self.moc.delete(cdNumbers.first(where: {$0.id == selectedItem})!)
// #####################################################################
}
try? self.moc.save()
// #####################################################################
// # Using Set<MyNumber>()
cdSelection = Set<MyNumber>()
// ######## OR ############
// # Using Set<UUID>()
// cdSelection = Set<UUID>()
// #####################################################################
}
// #####################################################################
// Core data selecction is affected by the presence of the cdOnSwipeDelete function
// IE: The selection column is shown in edit mode only if
// this functuion is referenced by ForEach{}.onDelete()
// #####################################################################
private func cdOnSwipeDelete(with indexSet: IndexSet) {
indexSet.forEach { index in
let number = cdNumbers[index]
self.moc.delete(number)
}
try? self.moc.save()
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
