#Published array in multiple ViewModels - SwiftUI - arrays

Question

I have app with only two Views, both Views has own ViewModel. ViewA shows and manipulate objects from selectedNumbers array. ViewB owns all available objects(numbers) - in this view I want manipulate selectedNumbers array, that is used by ViewA.
I'm trying to find out, how to share these selectedNumbers array between these two ViewModels. I tried to use EnvironmentObject, StaticObject etc. But nothing works as I need. What approach should I use to achieve desired result. Thanks for help!
import SwiftUI
struct ViewA: View {
#ObservedObject var viewModel = ViewModelA()
var body: some View {
VStack {
Text("\(viewModel.number)")
.font(.largeTitle)
.padding()
.onTapGesture {
viewModel.showNext()
}
ViewB()
}
}
}
class ViewModelA: ObservableObject {
var numbers: [Int] = []
#Published var number: Int
var index = 0
init() {
number = numbers.isEmpty ? 0 : numbers[index]
}
func showNext() {
guard !numbers.isEmpty else { return }
if index < numbers.count - 1 {
index += 1
} else {
index = 0
}
number = numbers[index]
}
}
struct ViewB: View {
#ObservedObject var viewModel = ViewModelB()
var body: some View {
HStack {
ForEach(viewModel.numbers, id: \.self) { number in
Text("\(number)")
.foregroundColor(viewModel.selectedNumbers.contains(number) ? .red : .black)
.onTapGesture {
viewModel.updateSelection(number)
}
}
}
}
}
class ViewModelB: ObservableObject {
#Published var numbers: [Int] = []
#Published var selectedNumbers: [Int] = []
init() {
numbers.append(contentsOf: [1,2,3,4,5,6,7,8])
}
func updateSelection(_ number: Int) {
if selectedNumbers.contains(number) {
selectedNumbers.remove(number)
} else {
selectedNumbers.append(number)
}
}
}
extension Array where Element: Equatable {
mutating func remove(_ object: Element) {
guard let index = firstIndex(of: object) else {return}
remove(at: index)
}
}

Answer 1

You can still keep the logic separate, but you need to keep a single source of truth, and if you want to share data among views, you either need to pass Bindings or you can also share #ObservedObject among Subviews.
import SwiftUI
struct ViewA: View {
#ObservedObject var viewModel = ViewModelA(modelB: ViewModelB())
var body: some View {
VStack {
Text("\(viewModel.number)")
.font(.largeTitle)
.padding()
.onTapGesture {
viewModel.showNext()
}
ViewB(model: viewModel)
}
}
}
class ViewModelA: ObservableObject {
var numbers: [Int] = []
#Published var number: Int
#Published var modelB:ViewModelB
var index = 0
init(modelB:ViewModelB) {
self.modelB = modelB
number = numbers.isEmpty ? 0 : modelB.selectedNumbers[index]
}
func showNext() {
guard !modelB.selectedNumbers.isEmpty else { return }
if index < modelB.selectedNumbers.count - 1 {
index += 1
} else {
index = 0
}
number = modelB.selectedNumbers[index]
}
}
struct ViewB: View {
#ObservedObject var model : ViewModelA
var body: some View {
HStack {
ForEach(model.modelB.selectedNumbers, id: \.self) { number in
Text("\(number)")
.foregroundColor(model.modelB.selectedNumbers.contains(number) ? .red : .black)
.onTapGesture {
model.modelB.updateSelection(number)
}
}
}
}
}
struct ViewModelB {
var selectedNumbers: [Int] = []
init() {
selectedNumbers.append(contentsOf: [1,2,3,4,5,6,7,8])
}
mutating func updateSelection(_ number: Int) {
if selectedNumbers.contains(number) {
selectedNumbers.remove(number)
} else {
selectedNumbers.append(number)
}
}
}
extension Array where Element: Equatable {
mutating func remove(_ object: Element) {
guard let index = firstIndex(of: object) else {return}
remove(at: index)
}
}