Navigation Title is not showing on SwiftUI - ios

Question

The navigationTitle is not working.
I use Swift5.5.2
In the preview there is no sign of the navigation title just an empty space.
struct ContentView: View {
#State private var firstname = ""
#State private var lastname = ""
#State private var birthdate = Date()
#State private var shouldSendNewsletter = false
var body: some View {
NavigationView {
Form {
Section(header: Text("Personal Information")) {
TextField("First Name", text: $firstname)
TextField("Last Name", text: $lastname)
DatePicker("Birth Date", selection: $birthdate, displayedComponents: .date)
Section(header: Text("Actions")) {
Toggle("Send Newsletter", isOn: $shouldSendNewsletter)
}//:Actions
}
}//:Form
}//: NAVIGATION VIEW
.navigationTitle("ABC")
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Preview of navigation title

Answer 1

NavigationView is a container that hold ChildViews inside it. So .navigationTitle resides inside NavigationView, so in order to change navigationTitle we must call it from inside of NavigationView like this
NavigationView{
VStack{
}
.navigationTitle("ABC")
}

Answer 2

.navigationTitle("ABC") should be attached to the topmost view inside your NavigationView:
NavigationView {
Form {
Section(header: Text("Personal Information")) {
TextField("First Name", text: $firstname)
TextField("Last Name", text: $lastname)
DatePicker("Birth Date", selection: $birthdate, displayedComponents: .date)
Section(header: Text("Actions")) {
Toggle("Send Newsletter", isOn: $shouldSendNewsletter)
} //: Actions
}
} //: Form
.navigationTitle("ABC") /// <- here!
} //: NAVIGATION VIEW