Add item to array if Bool = false - swiftui

Question

What i want to be able to do is to add items to an array if the Bool attached to them is true.
For example :
Here is my data model
struct ListModel: Identifiable, Hashable {
var id = UUID()
var name:String
var amount:Int
var code:String
var users:[User]
var items:[Item]
}
struct User: Identifiable, Hashable{
var id = UUID()
var foreName:String
var surName:String
var username:String
var pfp:String
}
struct Item:Identifiable, Hashable{
var id = UUID()
var name:String
var image:String?
var showItem:Bool
var amount:String
}
and when an the property showItem is true i want to add it to a new array
I have tried an approach like this
import SwiftUI
struct ListTest: View {
var list:ListModel
#State var nonHiddenItems:[Item] = []
var body: some View {
VStack{
ForEach(0..<list.items.count){item in
ItemView(item: list.items[item])
}
}
.onAppear(){
ForEach(0..<list.items.count){item in
if list.items[item].showItem == true{
nonHiddenItems.append(list.items[item])
}
}
}
}
}
struct ListTest_Previews: PreviewProvider {
static var previews: some View {
ListTest(list: ListModel(name: "Family Shopping", amount: 0, code: "1001", users: [User(foreName: "Elon", surName: "Musk", username: "Elon123", pfp: "Musk"), User(foreName: "Jeff", surName: "Bezos", username: "Jefferey", pfp: "Bezos")], items: [Item(name: "Cheese", image: "Pizza", showItem: true, amount: "5g"), Item(name: "Ham", showItem: false, amount: "5g")]))
}
}
But i get errors such as Type '()' cannot conform to 'View' on my ForEach loop
How can i fix m errors?
Many Thanks
Sean

Answer 1

A ForEach (uppercase) expression is a view builder, not a classic for loop. You cannot use ForEach in onAppear
Instead use forEach (lowercase)
(0..<list.items.count).forEach{ index in
if list.items[index].showItem == true{
nonHiddenItems.append(list.items[index])
}
}
or swiftier
nonHiddenItems = list.items.filter(\.showItem)

Answer 2

You should not use ForEach(...) in .onAppear(...) like you do.
I suggest you read the basics of SwiftUI here: https://developer.apple.com/tutorials/swiftui/
Try this approach:
struct ListTest: View {
var list: ListModel
#State var nonHiddenItems:[Item] = []
var body: some View {
VStack{
ForEach(list.items){ item in // <-- here
ItemView(item: item)
}
}
.onAppear{
for i in list.items.indices { // <-- here
if list.items[i].showItem {
nonHiddenItems.append(list.items[i])
}
}
}
}
}
EDIT-1: my guess is, what you probably wanted to do, is this:
struct ListTest: View {
var list: ListModel
var body: some View {
VStack {
ForEach(list.items.filter{$0.showItem}){ item in
ItemView(item: item)
}
}
}
}
This way you do not "duplicate" your source of truth array in ListModel.