#State variable is cleared once new SwiftUI view has been fully loaded - swiftui

Question

Whenever I call the view CardronaView() the #State variable will be loaded with the correct data for about 3 seconds then it will be reset back to it's default which is an empty string. How can I fix this? I am calling the new view with this:
NavigationView {
List {
// MARK: - Display Cardrona
NavigationLink(destination: CardronaView()) {
ZStack(alignment: .topLeading) {
Image("Cardrona-header")
Text("Cardrona").font(.largeTitle).fontWeight(.semibold).foregroundColor(Color.black)
Text(cardTemp).foregroundColor(Color.black).padding(.top, 50).font(.title3)
}
}
}
}
The code in the new view is this:
struct CardronaView: View {
#State var cardDate: String = ""
var body: some View {
List {
Text(cardDate)
}.onAppear {
Api().getJsonCard { (Cardrona) in
cardDate = "\(Cardrona.data_updated)"
}
}
}
}

Answer 1

When making a network request, it is good practice to perform it before loading the next view. There are many good reasons to do so, as in case the call is not successful, the new view is not loaded and avoid a bad user experience. This is where you show an alert to your user saying that the call couldn't be made.
If the network call succeeds, you pass your result to the new view and populate it.
As a network call is asynchronous and you make this call .onAppear, if the call is taking too long, you will see the empty String because your view as already been loaded.
I changed your code in a way that the network call is being made on the precedent view. But maybe you should add the code when the user taps the ListCell and if the call is successful, then the NavigationLink triggers its destination parameter, which is CardonaView(cardDate:).
struct ContentView: View {
#State var cardDate: String = ""
var body: some View {
NavigationView {
List {
// MARK: - Display Cardrona
NavigationLink(destination: CardronaView(cardDate: cardDate)) {
ZStack(alignment: .topLeading) {
Image("Cardrona-header")
Text("Cardrona").font(.largeTitle).fontWeight(.semibold).foregroundColor(Color.black)
Text(cardTemp).foregroundColor(Color.black).padding(.top, 50).font(.title3)
}
}
}
}
.onAppear {
Api().getJsonCard { (Cardrona) in
cardDate = "\(Cardrona.data_updated)"
}
}
}
struct CardronaView: View {
var cardDate: String
var body: some View {
List {
Text(cardDate)
}
}
}