SwiftUI List single selectable item - swiftui

Question

I'm trying to create a List and allow only one item to be selected at a time. How would I do so in a ForEach loop? I can select multiple items just fine, but the end goal is to have only one checkmark in the selected item in the List. It may not even be the proper way to handle what I'm attempting.
struct ContentView: View {
var body: some View {
NavigationView {
List((1 ..< 4).indices, id: \.self) { index in
CheckmarkView(index: index)
.padding(.all, 3)
}
.listStyle(PlainListStyle())
.navigationBarTitleDisplayMode(.inline)
//.environment(\.editMode, .constant(.active))
}
}
}
struct CheckmarkView: View {
let index: Int
#State var check: Bool = false
var body: some View {
Button(action: {
check.toggle()
}) {
HStack {
Image("Image-\(index)")
.resizable()
.frame(width: 70, height: 70)
.cornerRadius(13.5)
Text("Example-\(index)")
Spacer()
if check {
Image(systemName: "checkmark")
.resizable()
.frame(width: 12, height: 12)
}
}
}
}
}

Answer 1

You'll need something to store all of the states instead of storing it per-checkmark view, because of the requirement to just have one thing checked at a time. I made a little example where the logic is handled in an ObservableObject and passed to the checkmark views through a custom Binding that handles checking/unchecking states:
struct CheckmarkModel {
var id = UUID()
var state = false
}
class StateManager : ObservableObject {
#Published var checkmarks = [CheckmarkModel(), CheckmarkModel(), CheckmarkModel(), CheckmarkModel()]
func singularBinding(forIndex index: Int) -> Binding<Bool> {
Binding<Bool> { () -> Bool in
self.checkmarks[index].state
} set: { (newValue) in
self.checkmarks = self.checkmarks.enumerated().map { itemIndex, item in
var itemCopy = item
if index == itemIndex {
itemCopy.state = newValue
} else {
//not the same index
if newValue {
itemCopy.state = false
}
}
return itemCopy
}
}
}
}
struct ContentView: View {
#ObservedObject var state = StateManager()
var body: some View {
NavigationView {
List(Array(state.checkmarks.enumerated()), id: \.1.id) { (index, item) in //<-- here
CheckmarkView(index: index + 1, check: state.singularBinding(forIndex: index))
.padding(.all, 3)
}
.listStyle(PlainListStyle())
.navigationBarTitleDisplayMode(.inline)
}
}
}
struct CheckmarkView: View {
let index: Int
#Binding var check: Bool //<-- Here
var body: some View {
Button(action: {
check.toggle()
}) {
HStack {
Image("Image-\(index)")
.resizable()
.frame(width: 70, height: 70)
.cornerRadius(13.5)
Text("Example-\(index)")
Spacer()
if check {
Image(systemName: "checkmark")
.resizable()
.frame(width: 12, height: 12)
}
}
}
}
}
What's happening:
There's a CheckmarkModel that has an ID for each checkbox, and the state of that box
StateManager keeps an array of those models. It also has a custom binding for each index of the array. For the getter, it just returns the state of the model at that index. For the setter, it makes a new copy of the checkbox array. Any time a checkbox is set, it unchecks all of the other boxes. I also kept your original behavior of allowing nothing to be checked
The List now gets an enumeration of the state.checkmarks -- using enumerated lets me keep your previous behavior of being able to pass an index number to the checkbox view
Inside the ForEach, the custom binding from before is created and passed to the subview
In the subview, instead of using #State, #Binding is used (this is what the custom Binding is passed to)

Answer 2

List {
ForEach(0 ..< RemindTimeType.allCases.count) {
index in CheckmarkView(title:getListTitle(index), index: index, markIndex: $markIndex)
.padding(.all, 3)
}.listRowBackground(Color.clear)
}
struct CheckmarkView: View {
let title: String
let index: Int
#Binding var markIndex: Int
var body: some View {
Button(action: {
markIndex = index
}) {
HStack {
Text(title)
.foregroundColor(Color.white)
.font(.custom(FontEnum.Regular.fontName, size: 14))
Spacer()
if index == markIndex {
Image(systemName: "checkmark.circle.fill")
.foregroundColor(Color(hex: 0xe6c27c))
}
}
}
}
}

Answer 3

We can benefit from binding collections of Swift 5.5.
import SwiftUI
struct CheckmarkModel: Identifiable, Hashable {
var id = UUID()
var state = false
}
class StateManager : ObservableObject {
#Published var checkmarks = [CheckmarkModel(), CheckmarkModel(), CheckmarkModel(), CheckmarkModel()]
}
struct SingleSelectionList<Content: View>: View {
#Binding var items: [CheckmarkModel]
#Binding var selectedItem: CheckmarkModel?
var rowContent: (CheckmarkModel) -> Content
#State var previouslySelectedItemNdx: Int?
var body: some View {
List(Array($items.enumerated()), id: \.1.id) { (ndx, $item) in
rowContent(item)
.modifier(CheckmarkModifier(checked: item.id == self.selectedItem?.id))
.contentShape(Rectangle())
.onTapGesture {
if let prevIndex = previouslySelectedItemNdx {
items[prevIndex].state = false
}
self.selectedItem = item
item.state = true
previouslySelectedItemNdx = ndx
}
}
}
}
struct CheckmarkModifier: ViewModifier {
var checked: Bool = false
func body(content: Content) -> some View {
Group {
if checked {
ZStack(alignment: .trailing) {
content
Image(systemName: "checkmark")
.resizable()
.frame(width: 20, height: 20)
.foregroundColor(.green)
.shadow(radius: 1)
}
} else {
content
}
}
}
}
struct ContentView: View {
#ObservedObject var state = StateManager()
#State private var selectedItem: CheckmarkModel?
var body: some View {
VStack {
Text("Selected Item: \(selectedItem?.id.description ?? "Select one")")
Divider()
SingleSelectionList(items: $state.checkmarks, selectedItem: $selectedItem) { item in
HStack {
Text(item.id.description + " " + item.state.description)
Spacer()
}
}
}
}
}
A bit simplified version
struct ContentView: View {
#ObservedObject var state = StateManager()
#State private var selection: CheckmarkModel.ID?
var body: some View {
List {
ForEach($state.checkmarks) { $item in
SelectionCell(item: $item, selectedItem: $selection)
.onTapGesture {
if let ndx = state.checkmarks.firstIndex(where: { $0.id == selection}) {
state.checkmarks[ndx].state = false
}
selection = item.id
item.state = true
}
}
}
.listStyle(.plain)
}
}
struct SelectionCell: View {
#Binding var item: CheckmarkModel
#Binding var selectedItem: CheckmarkModel.ID?
var body: some View {
HStack {
Text(item.id.description + " " + item.state.description)
Spacer()
if item.id == selectedItem {
Image(systemName: "checkmark")
.foregroundColor(.accentColor)
}
}
}
}
A version that uses internal List's selected mark and selection:
import SwiftUI
struct CheckmarkModel: Identifiable, Hashable {
var name: String
var state: Bool = false
var id = UUID()
}
class StateManager : ObservableObject {
#Published var checkmarks = [CheckmarkModel(name: "Name1"), CheckmarkModel(name: "Name2"), CheckmarkModel(name: "Name3"), CheckmarkModel(name: "Name4")]
}
struct ContentView: View {
#ObservedObject var state = StateManager()
#State private var selection: CheckmarkModel.ID?
#State private var selectedItems = [CheckmarkModel]()
var body: some View {
VStack {
Text("Items")
List($state.checkmarks, selection: $selection) { $item in
Text(item.name + " " + item.state.description)
}
.onChange(of: selection) { s in
for index in state.checkmarks.indices {
if state.checkmarks[index].state == true {
state.checkmarks[index].state = false
}
}
selectedItems = []
if let ndx = state.checkmarks.firstIndex(where: { $0.id == selection}) {
state.checkmarks[ndx].state = true
selectedItems = [state.checkmarks[ndx]]
print(selectedItems)
}
}
.environment(\.editMode, .constant(.active))
Divider()
List(selectedItems) {
Text($0.name + " " + $0.state.description)
}
}
Text("\(selectedItems.count) selections")
}
}