How do I update a List in SwiftUI?

Question

My code is a little more complex than this so I created an example that gets the same error.

When I navigate into a view, I have a function I want to perform with a variable passed into this view. That function then produces an array. I then want to put that array into a List, but I get an error.

How do I get the List to show the produced array?

I think the issue is the List can't be updated because it already has the declared blank array.

struct ContentView : View {

    @State var array = [String]()

    var body: some View {
        List(self.array,id: \.self) { item in
            Text("\(item)")
            }
            .onAppear(perform: createArrayItems)
    }

    func createArrayItems() {
        array = ["item1", "item2", "item3", "item4", "item5"]
    }

}

Answer 1

You can use ObservableObject data providers(eg : ViewModel) with @Published properties.

struct ListView: View {
   @ObservedObject var viewModel = ListViewModel()

   var body: some View {
      NavigationView {
         List(){
            ForEach(viewModel.items) { item in
               Text(item)
            }
         }
      }  
   }
}



#if DEBUG

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
     ListView()
  }
}
#endif



class ListViewModel: ObservableObject {

   @Published var items = ["item1", "item2", "item3", "item4", "item5","item6"]

   func addItem(){
      items.append("item7")
   }
}

Answer 2

@txagPman

I too have your problem to understand how to modify a list. I was able to write this code. I hope it's useful.

    import SwiftUI

struct ContentView: View {

    @State private var array = createArrayItems()
    //     @State private var array = [""] - This work
    //    @State private var array = [] - This not work
    @State private var text = ""

    var body: some View {
        VStack {
            TextField("Text", text: $text, onCommit: {
//                self.array = createArrayItems() - This work after press return on textfield
                self.array.append(self.text)
            }).padding()
            List (self.array, id: \.self) {item in
                Text("\(item)")
            }
        }
//        .onAppear {
//            self.array = createArrayItems() - This not work
//        }
    }
}

func createArrayItems() -> [String] {
    return ["item_01","item_02","item_03","item_04" ]
}