ObservableObject not updating view in nested loop SWIFTUI - ios

Question

Regarding the following project :
You have an amountSum of 100
When you click on one user "plus" button, this specific user have to pay this amount but if you click on multiple user "plus" button, the amount to pay is divided between them equally.
Any idea how I can update the entire Model2.MustPayM2 prop when I click on the "plus" button please ?
import SwiftUI
struct Model1: Identifiable, Codable {
var id: String = UUID().uuidString
var nameM1: String
var amountM1: Double
var amountSumM1: Double = 100
var arrayM2: [Model2]
var isVisible: Bool = false
}
struct Model2: Identifiable, Codable {
var id: String = UUID().uuidString
var nameM2: String
var amountM2: Double = 0
var mustPayM2: Bool = false
}
class ViewModel1: ObservableObject {
#Published var Publi1: Model1
#Published var Publi1s: [Model1] = []
#Published var Publi2: Model2
#Published var Publi2s: [Model2] = []
init() {
let pub2 = Model2(nameM2: "init")
let pub1 = Model1(nameM1: "init", amountM1: 0, arrayM2: [pub2])
self.Publi2 = pub2
self.Publi1 = pub1
var newPub1s: [Model1] = []
for i in (0..<5) {
let newNameM1 = "name\(i+1)"
let newAmountM1 = Double(i+1)
var newModel1 = Model1(nameM1: newNameM1, amountM1: newAmountM1, arrayM2: [pub2])
var newPub2s: [Model2] = []
for i in (0..<5) {
let newNameM2 = "\(newNameM1)-user\(i+1)"
let newModel2 = Model2(nameM2: newNameM2)
newPub2s.append(newModel2)
}
newModel1.arrayM2 = newPub2s
newPub1s.append(newModel1)
}
Publi1s = newPub1s
Publi1 = newPub1s[0]
Publi2s = newPub1s[0].arrayM2
Publi2 = newPub1s[0].arrayM2[0]
}
}
struct View1: View {
#EnvironmentObject var VM1: ViewModel1
#State private var tt: String = ""
private let screenHeight = UIScreen.main.bounds.height
var body: some View {
ZStack {
VStack {
ForEach(0..<VM1.Publi2s.count, id: \.self) { i in
Text("\(VM1.Publi2s[i].nameM2)")
Text(tt)
Button {
VM1.Publi2s[i].mustPayM2.toggle()
var a = VM1.Publi2s.filter { $0.mustPayM2 == true }
let b = VM1.Publi1.amountM1 / Double(a.count)
// How can I update the new props between all users ??
// for j in 0..<a.count {
// a[j].amountM2 = b
// }
} label: {
Image(systemName: "plus")
}
}
Spacer()
Button {
VM1.Publi1.isVisible.toggle()
} label: {
Text("SHOW ME")
}
Spacer()
}
View2()
.offset(y: VM1.Publi1.isVisible ? 0 : screenHeight)
}
}
}
struct View2: View {
#EnvironmentObject var VM1: ViewModel1
var body: some View {
VStack {
Spacer()
ForEach(0..<VM1.Publi2s.count, id: \.self) { i in
Text("\(VM1.Publi2s[i].amountM2)")
}
}
}
}
struct View2_Previews: PreviewProvider {
static var previews: some View {
Group {
View1()
}
.environmentObject(ViewModel1())
}
}

Answer 1

You implementation seems overly complicated and error prone. I´ve practically rewritten the code for this. I´ve added comments to make it clear what and why I have done certain things. If you don´t understand why, don´t hesitate to ask a question. But please read and try to understand the code first.
//Create one Model containing the individuals
struct Person: Identifiable, Codable{
var id = UUID()
var name: String
var amountToPay: Double = 0.0
var shouldPay: Bool = false
}
//Create one Viewmodel
class Viewmodel:ObservableObject{
//Entities being observed by the View
#Published var persons: [Person] = []
init(){
//Create data
persons = (0...4).map { index in
Person(name: "name \(index)")
}
}
//Function that can be called by the View to toggle the state
func togglePersonPay(with id: UUID){
let index = persons.firstIndex { $0.id == id}
guard let index = index else {
return
}
//Assign new value. This will trigger the UI to update
persons[index].shouldPay.toggle()
}
//Function to calculate the individual amount that should be paid and assign it
func calculatePayment(for amount: Double){
//Get all persons wich should pay
let personsToPay = persons.filter { $0.shouldPay }
//Calcualte the individual amount
let individualAmount = amount / Double(personsToPay.count)
//and assign it. This implementation will trigger the UI only once to update
persons = persons.map { person in
var person = person
person.amountToPay = person.shouldPay ? individualAmount : 0
return person
}
}
}
struct PersonView: View{
//pull the viewmodel from the environment
#EnvironmentObject private var viewmodel: Viewmodel
//The Entity that holds the individual data
var person: Person
var body: some View{
VStack{
HStack{
Text(person.name)
Text("\(person.amountToPay, specifier: "%.2f")$")
}
Button{
//toggle the state
viewmodel.togglePersonPay(with: person.id)
} label: {
//Assign label depending on person state
Image(systemName: "\(person.shouldPay ? "minus" : "plus")")
}
}
}
}
struct ContentView: View{
//Create and observe the viewmodel
#StateObject private var viewmodel = Viewmodel()
var body: some View{
VStack{
//Create loop to display person.
//Dont´t itterate over the indices this is bad practice
// itterate over the items themselves
ForEach(viewmodel.persons){ person in
PersonView(person: person )
.environmentObject(viewmodel)
.padding(10)
}
Button{
//call the func to calculate the result
viewmodel.calculatePayment(for: 100)
}label: {
Text("SHOW ME")
}
}
}
}