I have two ways to navigate to make CreateWorkout View, one is the user creating a new workout by tapping on a button in the toolbar:

    .toolbar {
        NavigationLink() {
            AddWorkoutView()
        } label : {
            Image(systemName: "plus.circle")
                .resizable()
                   .frame(width: 24, height: 24)
        }

    }

The other is a User clicking on an existing workout in a list to edit it further:
List(workouts) { workout in

        NavigationLink {
            AddWorkoutView(workout: workout)
        } label: {
            VStack {
                Text(workout.name ?? "No name")
            }
        }
       
       
    }

how do I differentiate in my Create Workout View between editing an existing workout and creating a new one? so far I only have code for creating a new one and that is a create a temporary workout object that I will write to swiftData when the user presses the save button later but until then they are free to edit it:

struct AddWorkoutView: View {
    
    @Environment(.modelContext) var modelContext
    @State private var workoutName: String = ""
    @State private var showExercieSheet = false
    @State private var workoutStartTime = Date.now
    @State private var workoutEndTime = Date.now
    
    //I will build this temporary workout object then write it to the db
    @State private var workout: Workout = Workout(id: UUID())
 

I need a way of knowing if a workout has been passed or not so I can use that rather than creating a brand new one, is there any way to do this in SwiftData?