SwiftUI How to create LazyVStack with selection as List - swift

Question

I would like to have something like List(selection: ) in LazyVStack.
The problem is that I don't know how to manage the content to split in each element that it contains.
What I've tried to do:
public struct LazyVStackSelectionable<SelectionValue, Content> : View where SelectionValue : Hashable, Content : View {
let content: Content
var selection: Binding<Set<SelectionValue>>?
#Environment(\.editMode) var editMode
public init(selection: Binding<Set<SelectionValue>>?, #ViewBuilder content: () -> Content) {
self.content = content()
self.selection = selection
}
public var body: some View {
if self.editMode?.wrappedValue == EditMode.active {
HStack {
content //here I would like to have something like ForEach (content, id:\.self)
Button(action: {
//add the UUID to the list of selected item
}) {
Image(systemName: "checkmark.circle.fill")
//Image(systemName: selection?.wrappedValue.contains(<#T##member: Hashable##Hashable#>) ? "checkmark.circle.fill" : "circle")
}
}
}
else {
content
}
}
}
struct ListView: View {
#State private var editMode: EditMode = .inactive
#State private var selection = Set<UUID>()
#State private var allElements: [MyElement] = [MyElement(id: UUID(), text: "one"),
MyElement(id: UUID(), text: "two" ),
MyElement(id: UUID(), text: "tree" )
]
var body: some View {
NavigationView {
VStack {
Divider()
Text("LazyVStack")
.foregroundColor(.red)
LazyVStack {
ForEach(allElements, id: \.self) { element in //section data
Text(element.text)
}
}
Divider()
Text("LazyVStackSelectionable")
.foregroundColor(.red)
LazyVStackSelectionable(selection: $selection) {
ForEach(allElements, id: \.self) { element in //section data
Text(element.text)
}
}
Divider()
}
.environment(\.editMode, self.$editMode)
.navigationBarTitle(Text("LIST"), displayMode: .inline)
.navigationBarItems(//EDIT
trailing:
Group {
HStack (spacing: 15) {
self.editButton
self.delInfoButton
.contentShape(Rectangle())
}
}
)
}
}
//MARK: EDIT MODE
private func deleteItems() {
DispatchQueue.global(qos: .userInteractive).async {
Thread.current.name = #function
selection.forEach{ idToRemove in
if let index = allElements.firstIndex(where: { $0.id == idToRemove }) {
allElements.remove(at: index)
}
}
}
}
private var editButton: some View {
Button(action: {
self.editMode.toggle()
self.selection = Set<UUID>()
}) {
Text(self.editMode.title)
}
}
private var delInfoButton: some View {
if editMode == .inactive {
return Button(action: {}) {
Image(systemName: "square.and.arrow.up")
}
} else {
return Button(action: deleteItems) {
Image(systemName: "trash")
}
}
}
}
struct ListView_Previews: PreviewProvider {
static var previews: some View {
ListView()
}
}
edit = .inactive
edit = .active
UPDATE
with Asperi's solution, I lose the propriety of LazyVStack, all the rows are loaded also if not displayed (and is also not scrollable:
struct SampleRow: View {
let number: Int
var body: some View {
Text("Sel Row \(number)")
}
init(_ number: Int) {
print("Loading LazySampleRow row \(number)")
self.number = number
}
}
struct LazySampleRow: View {
let number: Int
var body: some View {
Text("LVS element \(number)")
}
init(_ number: Int) {
print("Loading LazyVStack row \(number)")
self.number = number
}
}
var aLotOfElements: [MyElement] {
var temp: [MyElement] = []
for i in 1..<200 {
temp.append(MyElement(id: UUID(), number: i))
}
return temp
}
struct ContentView: View {
#State private var editMode: EditMode = .inactive
#State private var selection = Set<UUID>()
#State private var allElements: [MyElement] = aLotOfElements//[MyElement(id: UUID(), number: 1)]
var body: some View {
NavigationView {
HStack {
VStack {
Text("LazyVStack")
.foregroundColor(.red)
ScrollView {
LazyVStack (alignment: .leading) {
ForEach(allElements, id: \.self) { element in //section data
LazySampleRow(element.number)
}
}
}
}
Divider()
VStack {
LazyVStack (alignment: .leading) {
Divider()
Text("LazyVStackSelectionable")
.foregroundColor(.red)
LazyVStackSelectionable(allElements, selection: $selection) { element in
SampleRow(element.number)
}
Divider()
}
}
}
.environment(\.editMode, self.$editMode)
.navigationBarTitle(Text("LIST"), displayMode: .inline)
.navigationBarItems(//EDIT
trailing:
Group {
HStack (spacing: 15) {
self.editButton
self.delInfoButton
.contentShape(Rectangle())
}
}
)
}
}
//MARK: EDIT MODE
private func deleteItems() {
DispatchQueue.global(qos: .userInteractive).async {
Thread.current.name = #function
selection.forEach{ idToRemove in
if let index = allElements.firstIndex(where: { $0.id == idToRemove }) {
allElements.remove(at: index)
}
}
}
}
private var editButton: some View {
Button(action: {
self.editMode.toggle()
self.selection = Set<UUID>()
}) {
Text(self.editMode.title)
}
}
private var delInfoButton: some View {
if editMode == .inactive {
return Button(action: {}) {
Image(systemName: "square.and.arrow.up")
}
} else {
return Button(action: deleteItems) {
Image(systemName: "trash")
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
extension EditMode {
var title: String {
self == .active ? NSLocalizedString("done", comment: "") : NSLocalizedString("edit", comment: "")
}
mutating func toggle() {
self = self == .active ? .inactive : .active
}
}

Answer 1

You need to create custom handled containers for all variants of desired content types.
Below is a demo of possible direction on the example of following content support (by example of List)
LazyVStackSelectionable(allElements, selection: $selection) { element in
Text(element.text)
}
Demo prepared and tested with Xcode 12 / iOS 14 (it is used some SwiftUI 2.0 features so if needed SwiftUI 1.0 support some more tuning will be needed)
struct LazyVStackSelectionable<SelectionValue, Content> : View where SelectionValue : Hashable, Content : View {
#Environment(\.editMode) var editMode
private var selection: Binding<Set<SelectionValue>>?
private var content: () -> Content
private var editingView: AnyView?
init(selection: Binding<Set<SelectionValue>>?, #ViewBuilder content: #escaping () -> Content)
{
self.selection = selection
self.content = content
}
var body: some View {
Group {
if editingView != nil && self.editMode?.wrappedValue == .active {
editingView!
} else {
self.content()
}}
}
}
extension LazyVStackSelectionable {
init<Data, RowContent>(_ data: Data, selection: Binding<Set<SelectionValue>>?, #ViewBuilder rowContent: #escaping (Data.Element) -> RowContent) where Content == ForEach<Data, Data.Element.ID, HStack<RowContent>>, Data : RandomAccessCollection, RowContent : View, Data.Element : Identifiable, SelectionValue == Data.Element.ID
{
self.init(selection: selection, content: {
ForEach(data) { el in
HStack {
rowContent(el)
}
}
})
editingView = AnyView(
ForEach(data) { el in
HStack {
rowContent(el)
if let selection = selection {
Button(action: {
if selection.wrappedValue.contains(el.id) {
selection.wrappedValue.remove(el.id)
} else {
selection.wrappedValue.insert(el.id)
}
}) {
Image(systemName: selection.wrappedValue.contains(el.id) ? "checkmark.circle.fill" : "circle")
}
}
}
}
)
}
}

Answer 2

Instead of creating custom LazyVStack I suggest to modify ContentView and pass bindings to it.
struct SampleRow: View {
let element: MyElement
let editMode: Binding<EditMode>
let selection: Binding<Set<UUID>>?
var body: some View {
HStack {
if editMode.wrappedValue == .active,
let selection = selection {
Button(action: {
if selection.wrappedValue.contains(element.id) {
selection.wrappedValue.remove(element.id)
} else {
selection.wrappedValue.insert(element.id)
}
}) {
Image(systemName: selection.wrappedValue.contains(element.id) ? "checkmark.circle.fill" : "circle")
}
}
Text("Sel Row \(element.number)")
}
}
init(_ element: MyElement,
editMode: Binding<EditMode>,
selection: Binding<Set<UUID>>?) {
print("Loading LazySampleRow row \(element.number)")
self.editMode = editMode
self.element = element
self.selection = selection
}
}
And then you can just wrap normal LazyVStack in ScrollView to achieve what you need.
ScrollView {
LazyVStack(alignment: .leading) {
ForEach(allElements, id: \.self) {
SampleRow($0,
editMode: $editMode,
selection: $selection)
}
}
}