SWIFTUI - OberservableObject class being set to nill each time called

Question

I am trying to learn Swift, and swiftUI.

I have a class : ObservableObject called within a button.

the class fetches some data, and stores it in a data var (an array of (string:any))

the class function fetch data is called within onAppear function in the main view VStack. the results of the function populates a list.

it all works fine, but each time I recall the view, the list empties itself.

here s the class opening

class fetchDataModel: ObservableObject {

@Published var datas:[data] = [data]()

now the datalist view :

struct allData: View {
@ObservedObject var datas =  fetchDataModel()

var body: some View {
    VStack{
        NavigationView {
            List(datas.data){ data in

                    NavigationLink(destination: data(data: data)){
                    HStack{
                        Text(data.someText)
                    }

                }
            }

        }
    }.navigationBarTitle(Text("Landmarks"))
        .onAppear(){
            self.datas.fetchData()

    }

}

}

I have a side menu that populates a motherView, once a button from the side menu is clicked, it calls datalist() (session is an environmentalObject)

if session.currentPage == "data" {
         myview =  AnyView(allDatas())

    } 

So I guess, each time I set myView to allDatas, it reinitialises the datas = fetchDataModel() class, and sets all its values to 0. Is there a way to avoid this problem ?