debug problem in Xcode13

struct ContentView: View {

    @State private var num = 0

    

    var body: some View {

        VStack{

        Text(String(num))

            .padding()

        Button(action: {

            num += 1

        }, label: {Text("click+1")})

        }

    }

}

Question 1:

If I run the code above on simulator, I could get the value of "num" on the console by using"po _num".

However, if I run the code in previews(by "Debug-Attach to process"), I only get the error"error: :3:1: error: cannot find '_num' in scope" on the console by using"po _num"

Xcode 13.2.1

Question 2:

I could use "po num"/"po _num" to get the value of "num" with Xcode 12.

BUT, only "po _num" works in Xcode13. "po num" will raise the error:" error: Couldn't lookup symbols: Preview2.ContentView.num.getter : Swift.Int"

Any help will be appreciated.